These are five questions and five answers.
1) Question 1. A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much calcium is contained in 40.0 g of calcium fluoride?
Answer:
20.5 g CaExplanation:
Calcium fluoride being a pure substance, has a fixed chemical compositon, which means that their elements (atoms), in any sample, are always in the same proportion.
Then, you can set the followoing proportion:
7.70 g Ca / 15.0 g CaF₂ = x / 40.0 g CaF₂Now, solve for x:
x = 40.0 g CaF₂ × 7.70 g Ca / 15.0 g CaF₂ = 20.5 g Ca.The answer must be expressed with 3 significan figures, since the three data are given with 3 significan figures.
2) Question 2. Silver has two isotopes. One isotope contains 60 neutrons and has a percent abundance of 51.839% the other contains 62 neutrons. Give the atomic symbols for the two isotopes.
Answer:
Isotope that contains 60 neutrons: ¹⁰⁷₄₇AgIsotope that contains 62 neutrons: ¹⁰⁹₄₇AgExplanation:
Isotopes are atoms of the same element, with different number of neutrons, so all the isotopes of an element have the same atomic number, Z (number of protons) and different mass number A (number of neutrons + protons).The atomic symbols for isotopes uses the chemical symbol of the atom (Ag for silver); a subscript to the left of the chemical symbol that represents the atomic mass (47 for silver); and a superscript to the left of the chemical symbol that represents the mass number.The mass number, A, for each silver isotope is calculated in this way:
Isotope that contains 60 neutrons: A = 60 + 47 = 107
Isotope that contains 62 neutrons: A = 62 + 47 = 109
Then, the respective atomic symboles are:Isotope with 60 neutrons: ¹⁰⁷₄₇Ag
Isotope with 62 neutrons: ¹⁰⁹₄₇Ag
3) Question 3. What is the average atomic weight of silver? What is the mass (in grams) of a single chlorine molecule?
Answer:
107.96 amuExplanation:
The atomic wieght of the elements is the weighted average weight of the different isotopes of the same element found in the nature, taking into account their relative abundance.
Average atomic weight = ∑( abundance × individual atomic weight)
Average atomic weight of silver = (abundace of isotope 1 × atomic weight isotope 1) + (abundance isotope 2 × atomic weight isotope 2)Abundance isotope 1 = 51.839%Atomic weight isotope 1 = mass number = 60 neutrons + 47 protons = 107 a.m.uAbundance isotope 2 = 100% - 51.839% = 48.161%Atomic weight isotope 2 = 62 neutrons + 47 protons = 109 a.m.u.Average atomic weight of silve = 107 amu × 51.839% + 109 amu × 48.161% = 107.96 amu4) Question without number: What is the mass (in grams) of a single chlorine molecule
Answer:
1.177 × 10⁻²² gExplanation:
The chlorine molecule is diatomic. That means that each molecule contains two atoms. The chemical formula of chlorine molecule is Cl₂.
The mass of one mole of molecules of Cl₂ is 2 × 35.453 g/mol = 70.906 g/mol
Mass of a single molecule = mass of one mol / number of molecules in one molMass of a single molecule = 70.906 g/mol / (6.022 × 10²³ molecules / mol)Mass of a single molecule = 11.77 × 10⁻²³ g = 1.177 × 10⁻²² g5) Question 4. How many moles of ethanol (CH₃CH₂OH) are in 141 mg?
Answer:
0.00301 molExplanation:
Molar mass of CH₃CH₂OH = 2 × 12.011 g/mol + 6 × 1.008 g/mol + 15.999 g/mol = 46.069 g/mol.Formula: number of moles = mass in grams / molar massCalculation: number of moles = 141 mg × ( 1 g /1000 mg) / (46.069 g/mol = 0.00301 molIn 40.0 g of calcium fluoride, there is 20.53 g of calcium. Silver has two isotopes represented by Ag-107 and Ag-109, with the average atomic weight of silver calculated by using their percent abundances. For ethanol, 141 mg corresponds to 0.00306 moles.
Calcium is contained in 40.0 g of calcium fluoride (CaF₂), we use a proportional relationship based on the information provided:
15.0 g of CaF₂ contains 7.70 g of calcium.
40.0 g of CaF₂ contains X g of calcium.
By setting up a proportion, we solve for X:
(7.70 g Ca / 15.0 g CaF₂) = (X g Ca / 40.0 g CaF₂)X = (7.70 g Ca / 15.0 g CaF₂)
40.0 g CaF₂)
X = 20.53 g of calcium.
The atomic symbols for the two isotopes of silver are: Ag-107 (47 protons + 60 neutrons) and Ag-109 (47 protons + 62 neutrons).
The average atomic weight of silver is calculated considering the weighted average of these isotopes and their percent abundances. The mass of a single chlorine molecule (Cl₂), not a chlorine atom, would be the sum of the atomic masses of the two chlorine atoms. However, the specific mass for a single molecule of Cl₂ in grams is a very small number, given that it's typically calculated in atomic mass units.
Finding the number of moles of ethanol (CH₃CH₂OH) in 141 mg:
The molar mass of ethanol is approximately 46.07 g/mol. Therefore:(141 mg) (Unit conversion from mg to g: 141 mg * (1 g/ 1000 mg)) (Divide by the molar mass of ethanol: (0.141 g) / 46.07 g/mol) = 0.00306 mol of ethanol.
Which of the following is an example of inertia?
An asteroid flying through the vacuum of space
A bullet striking a hard surface
A plane taking off from the runway
Catching a softball in a catcher's mitt
An asteroid flying through the vacuum of space is an example of inertia where it maintains its motion due to the absence of external forces except gravity. Other examples involving bullets, planes, and softballs are influenced by external forces and hence do not demonstrate inertia in its pure form.
Inertia and Its Examples
Inertia is the resistance of any physical object to a change in its velocity. This includes changes to the object's speed, or direction of motion. An object that isn't influenced by anything other than gravity is considered to be in an inertial frame of reference.
An example of inertia is an asteroid flying through the vacuum of space. This is because the asteroid will maintain its state of motion - traveling at a constant velocity - until acted upon by an outside force, such as another object's gravity. It fits the definition of an inertial frame as it is not being affected by any external forces except gravity, which doesn't change its velocity (considering the incredibly vast distances in space where gravitational influences are relatively minor).
In contrast, a bullet striking a hard surface, a plane taking off from the runway, and catching a softball in a catcher's mitt are all examples where external forces act on the objects, thereby affecting their motions and not illustrating a pure state of inertia.
A bullet striking a hard surface is an example of an object encountering a force that rapidly decelerates it.
A plane taking off is being propelled by the force generated by its engines.
Catching a softball involves an external force applied by the catcher's mitt to stop the ball.
There are 3 beakers each of which contains saline solution.
Beaker A initially contains 3 liters of 10\% salt solution.
Beaker B initially contains 2 liters of 20\% salt solution.
Beaker C initially contains 4 liters of 0\% salt solution.
Two liters are transferred from A to B and the result is thoroughly mixed. Then one liter is transferred from B to C and the result mixed. Finally two liters are transferred from C back to A. What is the percentage concetration of salt in A after all this?
Percentage concentration of salt in A=____ \%
Answer:
Percentage concentration of salt in A = 5.3%Explanation:
Assume all the concentrations are expressed in volumetric terms, i.e 10% = 10 liter salt / 100 liter solution, 20% = 20 liter salt / 100 liter soluton, 0% = 0 liters salt.
1) First transformation: 2 liters are from A to B
Solution A:
Concentration: 10 % salt ⇒ 10 liter salt / 100 liter solutionVolume of solution: 3 litersVolume of salt: 3 liters × 10 liter / 100 liters = 0.300 liter saltVolume of water: 3 liters - 0.300 liters = 2.700 liters solventSolution B:
Concentraion: 20%Volume of solution: 2 literVolume of salt: 2 liter × 0.20 = 0.4 liter saltVolume of water: 2 liter - 0.4 liter = 1.6 liter waterResultant mixture in beaker B: 2 liters of solution A plus 2 liters of solution B
Salt: 2 liter × 0.10 + 2 liter × 0.20 = 0.20 + 0.4 = 0.6 liter saltWater: 2 liter × 0.90 + 2 liter × 0.80 = 3.40 liter waterSolution: 2 liter + 2 liter = 4 liter solutionConcentration: 0.6 liter salt / 4 liter solution = 0.15 = 15%
2) Second transformation: 1 liter transferred from B to C
Salt: 1 liter × 0.15 + 0 = 0.15 liter salt↑ ↑
(from B) ( in C)
Solution: 1 liter + 4 liter = 5 liter solutionConcentration: 0.15 liter salt / 5 liter solution = 0.03 = 3.0%
3) Third transformation: 2 liters are from C to A.
Salt: 0.03 liter salt × 2 liter solution + 1 liter × 0.10 = 0.16 liter salt↑ ↑
(from C) (in A)
Solution: 2 liter + 1 liter = 3 liter solution% of salt in A = (0.16 liter salt / 3 liter solution) × 100 =5.3 %how does carbon dioxide malfunction
Answer:
if in excess the carbon dioxide is harmful to both the humen and other living things.
Explanation:
in our daily life we exhale carbon dioxide after inhaling oxygen.
but if carbon dioxide is in excess in atmosphere which is caused by burning fossils may cause changes in weather and climate at large due to aerosol particle emittion which inturn cause damage to o-zone layer causing global warming.which are effect to aquatic life and also to human.
Any reaction that absorbs 150 kcal of energy can be classified as ________.
a. endothermic
b. exothermic
c. activated
d. reduction
e. oxidation
Answer:
a. endothermic
Explanation:
Endothermic reaction: is a chemical reaction that absorbs heat or energy through the reaction.While, exothermic reaction: is a chemical reaction that releases energy through light or heat. It is the opposite of an endothermic reaction.So, Any reaction that absorbs 150 kcal of energy can be classified as a. endothermic.
Which of the following equations is balanced correctly and has the correct products for the reactants RbNO3 and BeF2?3RbNO3 + 3BeF2 → Be(NO3)3 + 3RbF, because Be increases in charge from 2+ to 3+ when it is replaced2RbNO3 + BeF2 → Be(NO3)2 + 2RbF, because Be keeps a 2+ charge throughout the reactionRbNO3 + BeF2 → BeNO3 + RbF2, because Be keeps a 1+ charge throughout the reaction2RbNO3 + BeF2 → Be(NO3)2 + 2RbF, because Be increases in charge from 1+ to 2+ when it is replaced
Answer:
2RbNO₃ + BeF₂ → Be(NO₃)₂ + 2RbF, because Be keeps a 2+ charge throughout the reaction.
Explanation:
It is a double replacement reaction.A double replacement reaction is a type of chemical reaction where two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products.In this reaction, there is no change in the oxidation state of different atoms.It is just a replacement reaction.So, the right choice is:2RbNO₃ + BeF₂ → Be(NO₃)₂ + 2RbF, because Be keeps a 2+ charge throughout the reaction.
Answer:
b
Explanation:
if a 25.0 ml sample of sulfuric acid is titrated with 50.0 ml of 0.200 M potassium hydroxide to a phenolphthalein endpoint, what is the molarity of the acid?
A) 0.150 M
B) 0.100 M
C) 0.200 M
D) 0.300 M
E) 0.400 M
Final answer:
The molarity of sulfuric acid when titrated with potassium hydroxide, given the volumes and molarity of KOH used, is calculated to be 0.200 M, option C.
Explanation:
To find the molarity of sulfuric acid (H₂SO₄) when titrated with potassium hydroxide (KOH), we use the equation for the reaction:
H₂SO₄ (aq) + 2KOH(aq) → K₂SO₄ (aq) + 2H₂O (l)
Note that the stoichiometry requires 2 moles of KOH to neutralize 1 mole of H₂SO₄. Given that 50.0 mL of 0.200 M KOH is used, we can calculate the moles of KOH used:
Moles of KOH = volume (L) × molarity (M) = 0.050 L × 0.200 M = 0.0100 molesSince it takes 2 moles of KOH to neutralize 1 mole of H₂SO₄, the moles of H₂SO₄ neutralized will be half that of KOH used:
Moles of H₂SO₄ = 0.0100 moles KOH ÷ 2 = 0.00500 molesFinally, to find the molarity of H₂SO₄ in the 25.0 mL sample:
Molarity of H₂SO₄ = moles of acid ÷ volume of solution (L) = 0.00500 moles ÷ 0.025 L = 0.200 MTherefore, the molarity of the sulfuric acid is 0.200 M, which corresponds to option C.
What is the basic building block of matter
Answer:
Atoms
Explanation:
Atoms are widely believed to be the most fundamental particle of matter and their basic building blocks. When atoms combines together, they form compounds. Molecules are another units of matter that are made up of tiny particles of atoms.
If aluminum is the limiting reactant, SOME/NONE/ALL of it will still be visible after the reaction completes. If CuCl2 is the limiting reactant,SOME/NONE/ALL of the aluminum will still be visible.
Answer:
If aluminum is the limiting reactant, NONE of it will still be visible after the reaction completes.
If CuCl2 is the limiting reactant, SOME of the aluminum will still be visible.
Explanation:
Any chemical reaction, if the reactants are not in equimolar ratios, contains limiting reactant and leftover reactant.The limiting reactant in a chemical reaction is the reactant that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by this reagent, since the reaction cannot continue without it.The leftover reactant is the reactant that is in excess and not consumed completely and some of it remains in the reaction mixture.So,
If aluminum is the limiting reactant, NONE of it will still be visible after the reaction completes.
and,
If CuCl2 is the limiting reactant, SOME of the aluminum will still be visible.
Answer:
If aluminum is the limiting reactant, none of it will still be visible after the reaction completes.
If CuCl2 is the limiting reactant, some of the aluminum will still be visible.
How many valence electrons does an iodine atom have
Answer:
An iodine atom has 7 valence electrons.Explanation:
Iodine is a halogen so it is the group (column number) 17 of the periodic table. It is a representative element.
The number of valence electrons for the representative elements is equal to the second digit of the group number. So, group 17 means that iodince has 7 valence electrons.
Now, more formally, the valence electrons are the electrons in the outermost shell of the atom and you can determine how many of them an atom has by doing the electron configuration.
These are the steps:
Atomic number, of iodine, Z = 53Number of electrons of the neutral atom = number of protons = 53Distribute the electrons in ascending order of orbital energies, following Aufbau's rules:1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵If you count the electrons you must obtain 53: 2 + 2 +6 + 2 + 6 + 2 + 10 + 6 + 2 + 10 + 5 = 53.The valence electrons are those in the highest principal energy level: 5s² 5p⁵, i.e 2 + 5 = 7.An iodine atom has seven valence electrons and generally gains one electron to become a negatively charged iodide ion (I-). Iodine is in the 17th group of the periodic table and prefers to achieve a full octet by accepting an additional electron rather than losing seven electrons.
An iodine atom has seven valence electrons. When looking to achieve a stable electronic configuration, iodine typically gains one electron to complete its octet because it is more energetically favorable than losing seven electrons. When an iodine atom gains an electron, it forms a negatively charged ion known as an iodide ion (I-). The formula of the resulting ion is I-.
The atomic number of iodine (53) reveals that a neutral atom of iodine consists of 53 protons and an equal number of electrons. Iodine is a halogen and is part of the 17th group in the periodic table which is characteristic of elements with seven valence electrons. According to the octet rule, atoms tend to bond in such a way that they each end up with eight valence electrons; gaining one electron is the preferred pathway for iodine.
The concept of a hypervalent structure involves molecules that contain more than eight electrons in their valence shell. However, in the case of the triiodide ion, resonance structures without violating the octet rule offer a more accurate representation of the bonding. As iodine tends to form weak bonds, the I2 molecule can dissociate into atomic iodine at a relatively lower energy compared to lighter halogens.
What do acidic solutions have high concentrations of?
Answer:
Hydrogen ions
Explanation:
Acidic solutions have high concentrations of hydronium ions and a lower concentration of hydroxide ions. The concentration of hydronium ions determines the acidity of the solution.
Explanation:Acidic solutions have high concentrations of hydronium ions (H+) and a proportionally lower concentration of hydroxide ions (OH-). This is due to the ionization of the acid, which releases H+ ions into the solution. The concentration of hydronium ions is a critical determinant of the solution's acidity.
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What is the oxidation state for a mn atom?
The oxidation state of a Mn atom in its elemental state is zero. However, in compounds, Mn has multiple potential oxidation states depending on the number of electrons it has lost.
Explanation:The oxidation state of an atom is typically zero when it is in its elemental state. In the case of a manganese (Mn) atom, this rule applies: the manganese atom has an oxidation state of zero.
However, this can change under certain conditions. For instance, in a chemical reaction, the oxidation state of Mn can vary. Transition metals like Mn usually have multiple oxidation states due to their ability to lose different numbers of d or s orbital electrons.
For example, in a compound such as MnO2, the oxidation state of Mn is +4. Here, Mn has lost four electrons. In another compound such as Mn2+, Mn has lost two electrons, giving it an oxidation state of +2.
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Final answer:
The oxidation state of Mn in the permanganate ion (MnO₄) is +7. This is calculated using the known oxidation state of oxygen (-2) and balancing it with the overall charge of the permanganate ion (-1).
Explanation:
The oxidation state of manganese (Mn) varies depending on the compound it is in. For instance, in the permanganate ion (MnO₄), the oxidation state of Mn is determined using the known oxidation state of oxygen, which is -2. Since there are four oxygen atoms, their combined oxidation state is -8. The permanganate ion itself carries an overall charge of -1, so when adding up the oxidation states of all atoms in the ion, their sum must equal this charge.
The calculation is as follows: Mn + (-2) × 4 = -1, which simplifies to Mn - 8 = -1. Solving for Mn gives us an oxidation state of +7. Therefore, in MnO₄, manganese has an oxidation state of +7. This demonstrates that manganese can have a high oxidation state and act as a strong oxidizing agent.
In other compounds, such as MnO₂ or Mn₂O₇, Mn may have different oxidation states, such as +4 or +7, respectively. The principle is to always include the charge on the atom, and balance the oxidation states with the overall charge of the compound or ion.
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What happens to the particles of a solid when the solid changes into a liquid?
A. They increase in size.
B. They decrease in size.
C. The attractive force between them increases.
D. The attractive force between them decreases.
Answer:
C
Explanation:
if you heat up a solid - you give it some energy. This causes the particles to move more and the solid to change into a liquid, or melt. If the liquid is heated then it may evaporate and turn into a gas. Taking energy away from a gas (cooling it down) may cause it to turn into a liquid - or condense.
Answer: D. The attractive force between them decreases.
Explanation:
Solid state : It is a state in which the particles are closely packed and does not have any space between them. They have strong intermolecular forces of attraction between them. This state has a definite shape and volume.
Liquid state : It is a state in which the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another.Theintermolecular forces are less as compared to the solids.This state has a definite volume but does not have a fixed shape.
Fusion process is a process where solid state changes to liquid state.The size of particles remain same but the attractive forces between them decrease, thus leading to a random motion of particles.
if you have 10 grams of a substance that decays with a half life of 14 days then how much will you have after 70 days?
Answer: If it has a 1/2 life of 14 days, after 14 days there will be half of it left correct?
Explanation:So, how many half-lifes are in 42 days?
42 / 14 = 3
This means it will divide 3 times.
1st half life period: 10 / 2 = 5g
2nd period: 5 / 2 = 2.5g
3rd period: 2.5 / 2 = 1.25g
10 g at start, 5 g at 14 days, 2.5 g at 28 days, 1.25 g at 42 days.
Answer: The amount of substance left will be 0.316 grams.
Explanation:
All the decay processes follow first order kinetics.
The equation used to calculate half life for first order kinetics:
[tex]t_{1/2}=\frac{0.693}{k}[/tex]
where,
[tex]t_{1/2}[/tex] = half life of the reaction = 14 days
k = ?
Putting values in above equation, we get:
[tex]k=\frac{0.693}{14days}=0.0495days^{-1}[/tex]
Rate law expression for first order kinetics is given by the equation:
[tex]t=\frac{2.303}{k}\log\frac{a}{y}[/tex]
where,
k = rate constant = [tex]0.0495days^{-1}[/tex]
t = time taken for decay process = 70 days
a = initial amount of the reactant = 10 grams
y = amount left after decay process = ? grams
Putting values in above equation, we get:
[tex]70days=\frac{2.303}{0.0495days^{-1}}\log\frac{10g}{y}\\\\y=0.316g[/tex]
Hence, the amount of substance left will be 0.316 grams.
A solution is made by mixing equal masses of methanol,
CH4O, and ethanol, C2H6O. How would you determine the mole fraction of each component to at least three significant figures?
Answer:
Mole fraction of methanol: 0.590 Mole fraction of ethanol: 0.410Explanation:
1) Definition of mole fraction: number of moles of a component / number of moles total number of moles.
2) The number of moles of each component is determined from the respective molar mass. Using the letter n for the number of moles of a component:
n = mass in grams / molar mass.3) CH₄O
n₁ = mass CH₄O / molar mass CH₄OMolar mass CH₄O = 32.04 g/mol
n₁ = mass CH₄O / 32.04 g/mol
4) C₂H₆O
n₂ = mass of C₂H₆O / molar mass of C₂H₆OMolar mass C₂H₆O = 46.07 g/mol
n₂ = C₂H₆O = mass of C₂H₆O / 46.07 g/mol
5) Both masses are equal; call them m.
n₁ = m / 32.04 n₂ = m / 46.07 n₁ + n₂ = m / 32.04 + m / 46.076) Mole fraction of CH₄O:
Use the letter X for mole fraction.
X₁ = n₁ / [n₁ + n₂] = [ m / 32.04 ] / [ m / 32.04 + m / 46.07]Cancel the common factor m:
X₁ = [ 1 / 32.04] / [1 / 32.04 + 1 /46.07] = 0.590
7) Mole fraction of C₂H₆O
X₁ + X₂ = 1 ⇒ X₂ = 1 - X₁= 1 - 0.590 = 0.410The mole fractions are rounded to three significant figures.
Which combination is the best choice to prepare a buffer with a ph of 9.0? which combination is the best choice to prepare a buffer with a of 9.0? nh3; nh4cl (pkb for nh3 is 4.75) hcho2; nacho2 (pka for hcho2 is 3.74) c5h5n; c5h5nhcl (pkb for c5h5n is 8.76) hno2;nano2 (pka for hno2 is 3.33)?
Answer:
[tex]\boxed{\text{NH$_{3}$; NH$_{4}$Cl}}[/tex]
Explanation:
The best choice to prepare a buffer of pH 9.0 is a conjugate acid/base pair in which the acid has pKₐ = 9.0 ± 1.
Let's examine each of the choices.
A. NH₃/NH₄Cl
For NH₃, = pK_b = 4.75
For NH₄⁺, pKₐ 14.00 - 4.75 = 9.25
B. HCHO₂/NaCHO₂
For HCHO₂, pKₐ = 3.74
C. C₅H₅N/ C₅H₅NHCl
For C₅H₅N, = pK_b = 8.76
For C₅H₅N⁺, pKₐ 14.00 – 8.76 = 5.21
D. HNO₂/NaNO₂
For HNO₂, pKₐ = 3.33
The only acid with a pKₐ close to 9.0 is the ammonium ion.
The best buffer to prepare a buffer with pH 9.0 is [tex]\boxed{\text{NH$_{3}$; NH$_{4}$Cl}}[/tex]
From the given options, the best combination to prepare a buffer with a PH of 9.0 is given by;
Option 1; NH₃;NH₄Cl
A buffer solution is defined as an aqueous solution that consists of a mixture of a weak acid and its conjugate base or mixture of a weak base and its' conjugate acid.Now, we want to find the best choice to prepare a buffer of pH 9.0. Thus, let us look at each option;
Option 1; NH₃;NH₄Cl
We are given that pK_b for NH₃ is 4.75
Thus pKₐ for NH₄ is;
NH₄; pKₐ = 14.00 - 4.75
NH₄; pKₐ = 9.25
Option 2; HCHO₂; NaCHO₂
We are given that pK_a for HCHO₂ is 3.74
HCHO₂; pKₐ = 3.74
Option 3; C₅H₅N; C₅H₅NHCl
We are given that pK_b for C₅H₅N is 8.76
Thus
For C₅H₅N, = pK_b = 8.76
Thus, pKₐ for C₅H₅N is;
C₅H₅N; pKₐ = 14.00 – 8.76
C₅H₅N; pKₐ = 5.21
Option 4; HNO₂;NaNO₂
We are given pKₐ for HNO₂ as 3.33
HNO₂; pKₐ = 3.33
Looking at all the pKₐ values, the only acid that has a pKₐ close to 9.0 is NH₄ with a pKₐ of 9.25.
In conclusion, the best combination to prepare a buffer with pH of 9.0 is
NH₃;NH₄Cl
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How many copies of F2 are required to balance this chemical equation? N2 + __F2 = 2NF3 a) 3 b) 4 c) 5 d) 6
Answer: a) 3
On the right side of the equation you have 6F, so you need 3 copies of F2 to balance the equation.
Answer:
a) 3
Explanation:
The unbalanced combustion reaction is shown below as:-
[tex]N_2+F_2\rightarrow 2NF_3[/tex]
On the left hand side,
There are 2 nitrogen atoms and 2 fluorine atoms
On the right hand side,
There are 2 nitrogen atoms and 6 fluorine atoms
Nitrogen atoms are balanced and only fluorine atoms have to be balanced by applying a stoichiometric coefficient of 3 in from of [tex]F_2[/tex] in the reactant side.
Thus, the balanced reaction is:-
[tex]N_2+3F_2\rightarrow 2NF_3[/tex]
Coefficient in front of the [tex]F_2[/tex] in the balanced equation - 3
The combustion of ________ has added great quantities of carbon dioxide to the atmosphere.
Answer:
fossil fuel combustion
Explanation:
Fossil fuel is the source of energy that drives almost all industrial processes on the surface of earth. Burning of these fuels releases energy for use in automobiles, industries, homes e.t.c. The complete combustion of these fuels in the presence of oxygen liberates carbon-dioxide and water with heat energy.
Fossil fuels are to a large extent hydrocarbon compounds and their derivatives. They form from organisms million of years ago. When organic matter is prevented from decay in an oxic or oxygen rich environment, they are able to conserve and preserve the energy in them for a vast duration in geologic time. This preserved energy is what becomes available during combustion.
Some of the fossil fuels are oil, natural gas, coal, e.t.c.
Upon combustion, a compound containing only carbon and hydrogen produces 2.67 g[tex]CO_{2}[/tex] and 1.10 g[tex]H_{2}O[/tex]. Find the empirical formula of the compound.
Answer:
[tex]\boxed{\text{CH$_{2}$}}[/tex]
Explanation:
1. Calculate the mass of each element
[tex]\text{Mass of C} = \text{2.67 g } \text{CO}_{2}\times \dfrac{\text{12.01 g C}}{\text{44.01 g }\text{CO}_{2}}= \text{0.7286 g C}\\\\\text{Mass of H} = \text{1.10 g }\text{H$_{2}$O}\times \dfrac{\text{2.016 g H}}{\text{18.02 g } \text{{H$_{2}$O}}} = \text{0.1231 g H}[/tex]
2. Calculate the moles of each element
[tex]\text{Moles of C = 0.7286 g C}\times\dfrac{\text{1 mol C}}{\text{12.01 g C }} = \text{0.060 67 mol C}\\\\\text{Moles of H = 0.1231 g H} \times \dfrac{\text{1 mol H}}{\text{1.008 g H}} = \text{0.1221 mol H}[/tex]
3. Calculate the molar ratios
Divide all moles by the smallest number of moles.
[tex]\text{C: } \dfrac{0.06067}{0.06067}= 1\\\\\text{H: } \dfrac{0.1221}{0.06067} = 2.015[/tex]
4. Round the ratios to the nearest integer
C:H = 1:2
5. Write the empirical formula
The empirical formula is [tex]\boxed{\text{CH$_{2}$}}[/tex]
The empirical formula of the compound is CH.
To find the empirical formula of the compound, we need to determine the molar ratios of carbon and hydrogen in the compound based on the masses of carbon dioxide (CO₂) and water (H₂O) produced during combustion.
First, we calculate the moles of carbon in CO₂:
The molar mass of CO₂ is 44.01 g/mol (12.01 g/mol for C and 2 × 16.00 g/mol for O₂).
Moles of CO₂ = 2.67 g / 44.01 g/mol = 0.0607 mol
Since there is one mole of carbon in one mole of CO₂, the moles of carbon are also 0.0607 mol.
Next, we calculate the moles of hydrogen in H₂O:
The molar mass of H₂O is 18.015 g/mol (2 × 1.008 g/mol for H₂ and 16.00 g/mol for O).
Moles of H₂O = 1.10 g / 18.015 g/mol = 0.0611 mol
The moles of hydrogen:
Moles of H in H₂O = 2 × Moles of H₂O = 2 × 0.0611 mol = 0.1222 mol
Now, let's re-calculate the molar ratio of carbon to hydrogen:
Moles of C / Moles of H = 0.0607 mol / 0.1222 mol = 1/2
This ratio simplifies to:
C: 1
H: 1
Therefore, the correct empirical formula of the compound is CH, not CH₂ as previously stated. The error in the initial calculation has been corrected, and the correct empirical formula is CH.
What happens to a reaction at equilibrium when more reactant is added to the system?
Answer:
When more reactant is added to a system at equllibrium more product is produced.Explanation:
Provided all other conditons remain constant (e.g. volume and temperature), the addition of more reactant means the increase of the concentration of the reactant, and so, at constant temperature, more product must be produced to compensate such addition of more reactant.
An equlibrium reaction may be represented by the general expression:
aA + bB ⇄ cC + dDAnd the equilibrium constant is given by:
[tex]Keq=\frac{[C]^c.[D]^d}{[A]^a.[B]^b}[/tex]Thus, since at constant temperature Kea is constant, the increase of a reactant concentration (A or B are in the denominator) means that the concentration of the products (C and D in the numerator) must increase.
Since, the molecular point of view what happens is that the increase of the concentration of reactions increase the rate of the direct (forward) reaction yielding to the production of more products.
Final answer:
Adding more reactant to a reaction at equilibrium causes the system to shift right, increasing the rate of the forward reaction and leading to the formation of more products until a new equilibrium is established, with the equilibrium constant (Kc) remaining unchanged.
Explanation:
When a chemical reaction has reached equilibrium, adding more reactant to the system causes the equilibrium to shift. The concepts behind this phenomenon are encapsulated by Le Châtelier's Principle, which states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.
In the case where more reactant is added, the equilibrium will shift to the right, meaning that the reaction system will respond by forming more products to relieve the stress caused by the added reactant. This increase in reactant concentration results in a temporary increase in the rate of the forward reaction compared to the reverse reaction, leading to a consumption of the added reactant and an increase in product concentration until a new equilibrium is established.
After the system readjusts, the reaction quotient (Qc) will once again equal the equilibrium constant (Kc), which remains unchanged as it is only affected by temperature. This adjustment process continues until the rate of the forward reaction and the rate of the reverse reaction are equal again. In essence, by adding more of a reactant, one can temporarily push the reaction to produce more products, a strategy often used in industrial processes to increase yield.
You are running a lemonade stand with your friend. You prepared 10 liters of 0.7 molarity lemonade, but your friend did online research and found that people prefer 0.4 Molarity lemonade. How can you fix the lemonade you made so that it is 0.4 Molarity without starting over?
Answer:
add 7.5L of water
Explanation:
M1×V1=M2×V2
M is molarity, V is volume
0.7 × 10 = 0.4 × V2
V2= 17.5L
vol. of water to add= 17.5 - 10 = 7.5L
The volume which is required to prepare 0.4M lemonade is 17.5L.
How do we calculate the required volume?Required volume of the solution will be calculated by using the below equation as:
M₁V₁ = M₂V₂, where
M₁ & V₁ are the molarity and volume of initial lemonade.
M₂ & V₂ are the molarity and volume of final prepared lemonade.
On putting all values from the question, we get
V₂ = (0.7)(10) / (0.4) = 17.5 L
Hence required volume of final lemonade is 17.5 L.
To know more about molarity & volume, visit the below link:
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Consider the titration curve below
If an Erlenmeyer flask that is used in this titration contains 40.0 mL of 0.10 M HCl, how many moles of hydrogen ions are present at the point that is labeled A on the graph?
OPTION A) 0.0025
OPTION B) 0.0040
OPTION C) 40.0
OPTION D) 4000
i think A because .10 divided by 40 would be .0025
Answer:
0.0040
Explanation:
The health of bones depends upon a good supply of calcium. If a person consumes 0.06 g of calcium, how many moles of calcium did he consume? A. 6.6 x 102 mol B. 7.5 x 10-2 mol C. 2.4x 101 mol D. 1.5 x 10-3 mol
Answer:
[tex]\boxed{\text{D. }1.5 \times 10^{-3}\text{ mol}}[/tex]
Explanation:
1 mol of Ca = 40.08 g
[tex]\text{Moles of Ca = 0.06 g Ca} \times \dfrac{\text{1 mol Ca}}{\text{40.08 g Ca}} = 1.5 \times 10^{-3}\text{ mol Ca}\\\\\text{The person consumed }\boxed{1.5 \times 10^{-3}\text{ mol Ca}}[/tex]
Final answer:
By dividing the mass of calcium consumed (0.06 g) by its molar mass (40.08 g/mol), we calculate that the individual consumed 1.5 x 10⁻³ moles of calcium, corresponding to option D.
Explanation:
The health of bones is strongly tied to adequate calcium intake, which is crucial during periods of bone growth and density increase, such as adolescence. To calculate the number of moles of calcium consumed when a person ingests 0.06 g, we need to use the molar mass of calcium. The molar mass of calcium is approximately 40.08 g/mol.
To find the number of moles (n), we use the formula:
n = mass (g) / Molar mass (g/mol)
For calcium:
n = 0.06 g / 40.08 g/mol = 1.5 x 10⁻³ moles
Therefore, the person consumed 1.5 x 10⁻³ moles of calcium, which corresponds to option D.
The chart shows the path reactants take to become products. Which statement best describes the chart? A. Heat was removed from the activation energy to create the product. B. Heat was added to create the product. C. The products have less energy than the reactants. D. The products have the same energy as the reactants.
Answer:
B
Explanation:
The final position of the curve is higher than the original height of the curve, meaning the products have more energy than the reactants.
Hence energy was added for the reactants to become the products. This is why the reaction is endothermic, because the products retained some of the supplied energy.
Part of the energy supplied was used to overcome the activation energy (the peak of the curve). However, this extra energy is recuperated as heat once the product is formed.
Answer:
B-
Heat was added to create the product
Explanation:
Just did the quiz on edg
Conduction occurs more easily between solids and liquids. This is because the particles in gases are
Answer:
farther apart and move faster.
Explanation:
A 100-kg moving at 15 m/s collides with a 50-kg cart at rest causing both cars to move together in the same direction. If momentum is conserved, at what speed are the two carts now moving?
Answer:
30m/s
Explanation:
100 / 50 = 2 * 15 = 30m/s
Answer:
[tex]\boxed{\text{10 m/s}}[/tex]
Explanation:
Data:
Cart 1: m₁ = 100 kg; v =15 m/s
Cart 2: m₂ = 50 kg; v₂ = ?
Calculations:
I assume that the two carts are going at the same speed v₂ after the collision.
[tex]\begin{array}{rcl}\text{Momentum before collision} & = & \text{Momentum after collision} \\\text{100 kg} \times\text{15 m/s} & = &\text{100 kg} \times v_{2} + \text{50 kg} \times v_{2}\\\text{1500 m/s} & = & 100 v_{2} +50 v_{2}\\\text{1500 m/s} & = & 150 v_{2}\\v_{2}& =&\textbf{10 m/s}\\\end{array}\\\\\text{The two carts are now moving at a speed of }\boxed{\textbf{10 m/s}}[/tex]
In a nonpolar covalent bond,
protons are shared equally by two atoms.
electrons are shared equally by two atoms.
electrons are shared unequally by two atoms.
protons are transferred from one atom to another.
Which molecule below has a triple covalent bond?
Diatomic Fluorine
Diatomic Nitrogen
Diatomic Oxygen
Diatomic Hydrogen
Answer:
#11: In a nonpolar covalent bond, electrons are shared equally between two atoms.
#12: Only the diatomic nitrogen molecule [tex]\rm N_2[/tex] contains a triple covalent bond among the four molecules.
Explanation:
#11Consider: what is a covalent bond?
Two atoms share a pair of electrons (called a bonding pair as opposed to a lone pair) between them.
Nonpolar covalent bonds exist only between atoms with similar electronegativity values. The two bonding atoms attract the bonding pair with similar strength, such that the bonding pair is shared mostly equally between the two atoms.
In case the two atoms differ in their electronegativity, the bonding pair will be closer to the more electronegative atom. That will make a polar covalent bond.
#12Atoms share electrons with each other to achieve an octet of eight valence electrons (two for hydrogen.) Atoms form a covalent bond for every two valence electrons that they need.
Consider: how many electrons do atoms in each molecule need to gain before achieving an octet?
Fluorine is in group 17 of the new IUPAC periodic table. Each fluorine atom needs 18 - 17 = 1 valence electron to achieve an octet. There are two fluorine atoms in an [tex]\rm F_2[/tex] molecule. These two atoms will need two electrons in total to achieve an octet. They will thus need to form [tex]2/2 = 1[/tex] covalent bond.
Similarly:
Nitrogen is in group 15.Each Nitrogen atom is 18 - 15 = 3 electrons away from an octet.There are two nitrogen atoms in each [tex]\rm N_2[/tex] molecule. The two nitrogen atoms need six more electrons in total and will form [tex]6/2 =3[/tex] covalent bonds.Oxygen is in group 16.Each oxygen atom is 18 - 16 = 2 electrons away from an octet.There are two oxygen atoms in each [tex]\rm O_2[/tex] molecule. The two oxygen atoms need four more electrons in total and will form [tex]4/2 =2[/tex] covalent bonds.Hydrogen is a special case in the "octet" rule.Each hydrogen atom needs one valence electron to attain the electron configuration of the next noble gas element, He. There are two hydrogen atoms in each [tex]\rm H_2[/tex] molecule. The two hydrogen atoms need two more electrons in total and will form [tex]2/2 =1[/tex] covalent bonds.Answer:
11. Electrons are shared equally by two atoms.
12. Diatomic nitrogen
Explanation:
An example of the the first bond is the diatomic hydrogen.
There are 5 electrons in the nitrogen atom's outer shell. The 2 nitrogen atoms will each share 3 electrons to form 3 covalent bonds.
What happens to a glucose molecule when it loses a hydrogen atom as the result of an oxidation-reduction reaction?
Answer: oxidized
Explanation:
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
oxidized.
Good luck! and sorry if is not the answer ur looking 4!
Answer:
The glucose molecule is oxidized
Explanation:
When glucose loses a hydrogen atom it is losing 1 proton and 1 electron. As it is losing an electron, the glucose is oxidized.
the elements lithium and oxygen react explosively to form lithium oxide,Li2O. how many moles of lithium oxide will form if 4.37 mol of lithium tract?
4Li(s) +O2(g) -> 2Li2O(s)
From the equation,
4 mole of lithium produces 2 mole of lithium oxide
4.37 mol of lithium produces (4.37÷4)x2 mol of lithium oxide
In the electrolysis of brine, the substances produced at the cathode are _____.
oxygen gas and hydroxide ions
sodium metal and hydrogen gas
chlorine gas and hydrogen gas
hydrogen gas and hydroxide ions
Answer:
In the electrolysis of brine, the substances produced at the cathode are sodium metal and hydrogen gas.
Explanation:
In the electrolysis of brine (Sodium chloride solution) using carbon as electrode, Chlorine gas is produced in the positive electrode (anode), while hydrogen gas is produced in the negative electrode (cathode).
Again, in the electrolysis of molten sodium chloride, chlorine gas is produced in anode, while sodium metal is produced in the cathode.
Nacl ⇄ Na⁺ + Cl⁻
Case 1: Molten Nacl
Anode(+ve) Product | Cathode (-ve) product
Cl⁻ -----> Cl + e⁻ | Na⁺ + e⁻ ---------> Na
Cl + Cl ------> Cl₂
Case 2: Nacl solution
Anode(+ve) Product | Cathode (-ve) Product
Cl⁻ -----> Cl + e⁻ | H⁺ + e⁻ ---------> H
Cl + Cl ------> Cl₂ | H + H ------------> H₂
Thus, cathodic products of electrolysis of brine are sodium metal and hydrogen gas
What is the volume in liters of 0.500 mol of c3h8 gas at stp
Answer:
11.21 L.
Explanation:
We can use the general law of ideal gas: PV = nRT.where, P is the pressure of the gas in atm (P = 1.0 atm, Standard P).
V is the volume of the gas in L (V = ??? L).
n is the no. of moles of the gas in mol (n = 0.5 mol).
R is the general gas constant (R = 0.0821 L.atm/mol.K),
T is the temperature of the gas in K (T = 273 K, Standard T).
∴ V = nRT/P = (0.5 mol)(0.0821 L.atm/mol.K)(273 K)/(1.0 atm) = 11.21 L.