How does the scientific method help scientists?

Answer:- The mole ratio of D to A is 3:2.

Explanations:- Mole ratio for a chemical equation is the ratio of the coefficients of the molecules. Coefficients are the numbers used to balance the chemical equations.

For the given generic chemical equation, the coefficient of molecule A is 2 and the coefficient of D is 3. It means 2 molecules of A react with 3 molecules of D. So, the mole ratio of A to D is 2:3.

Since, we are asked about the mole ratio of D to A so we will write the coefficient of D first and hence the mole ratio of D to A is 3:2.

Chemical change accurs when a substance changes form like liquid to solid.

Answer:

10.3 °C

Step-by-step explanation:

This is an isolated system so

heat gained by ice + heat lost by water = 0

Heat to warm ice + heat to melt ice + heat to warm melt + heat lost by water = 0

     q₁     +     q₂        +      q₃      +     q₄      = 0

n₁C₁ΔT₁ + n₁ΔH_fus + n₁C₃ΔT₃ + n₄C₃ΔT₄  = 0

Step 1: Calculate q₁

n₁ = 40.0 g × 1/18.02

n₁ = 2.220 mol

C₁ = 37.7 J·K⁻¹mol⁻¹

ΔT₁ = T_f – T_i  

ΔT₁ = 0.0 – (-15)

ΔT₁ = 15 °C = 15 K

q₁ = 2.220 × 37.7 × 15  

q₁ = 1255 J

q₁ = 1.255 kJ

===============

Step 2. Calculate q₂

ΔH_fus = 6.01 kJ·mol⁻¹

q₂ = 2.220 × 6.01

q₂ = 13.34 kJ

===============

Step 3: Calculate q₃

C₃ = 75.3 J·K⁻¹mol⁻¹

ΔT₃ = T_f – T_i  = x – 0 °C  

ΔT₃ = x °C = x K

q₃ = 2.220 × 75.3 × x

q₃ = 167x J

q₃ = 0.167x kJ

===============

Step 4. Calculate q₄

n₄ = 265 × 1/18.02

n₄ = 14.71 mol

ΔT₄ = T_f – T_i  = x – 25.0 °C  

q₄ = 14.71 × 75.3 × (x – 25.0)

q₄ = 1107 × (x – 25.0)

q₄ = 1107x  – 27 680 J

q₄ = 1.107x – 27.68 kJ

===============

Step 5. Solve for x

1.255 + 13.34 + 0.167x + 1.107x - 27.68 = 0

1.274x - 13.08 = 0

1.274x = 13.08

x = 13.08/1.274

x = 10.3 °C

The final temperature is -10.3 °C.

Answer:- [tex]1s^22s^22p^63s^23p^6[/tex]

Explanations:- Atomic number of chlrone(Cl) is 17 it means it has 17 electrons. It's electron configuration is: [tex]1s^22s^22p^63s^23p^5[/tex] .

Chloride ion is formed when Cl accepts one electron:

[tex]Cl+e^-\rightarrow Cl^-[/tex]

So, electrons for the chloride ion = 17+1 = 18

If we look at the electron configuration of Cl then 3p is still vacant as there are 5 electrons in it and it could have maximum 6 electrons. So, this 18th electron goes to 3p and the electron configuration of chloride ion becomes:

[tex]1s^22s^22p^63s^23p^6[/tex] .

Electrons is your answer

Answer: C.

electrons

Explanation: edmentum

Wind, air that moves to the ground

Usually poorly, especially at room temperature for most of them. The gases do not conduct. Some that are marginally non metals (silicon germanium and graphite) conduct passably well but do not conduct as well as copper or silver.

Non metals do not have easily freed electrons and that is why they do not conduct electricity.

Valcano i your answer i believe

Based on the question and the given data, philosophy and religion.

    The grams of  Fe₂O₃   that are formed is  47.68 g

calculation

Step 1: write   the equation for reaction

4 Fe +3O₂ → 2 Fe₂O₃

Step 2: find  the  moles  of Fe

moles = mass÷  molar mass

 = 33.4 g÷55.8 g/mol =0.5986 moles

Step 3 : use the mole ratio to determine the moles of Fe₂O₃

That is  from  equation above Fe:Fe₂O₃  is 4:2 therefore the moles of Fe₂O₃ is  =  0.5986 moles x 2/4 =0.2993 moles

Step 4 : find the mass  of Fe₂O₃

mass = mass x molar mass

The molar mass of Fe₂O₃  = (55.8 x 2 +(15.9 x3) = 159.3 g/mol

mass is therefore =  0.2993 moles x 159.3 g/mol =47.68 g

Answer:

47.8 g

Explanation:

A reaction that gives off heat energy is called Exothermic. (Answer).

A reaction that absorbs heat from the surroundings is called endothermic.

Answer: Exothermic

Explanation:

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and [tex]\Delta H[/tex] for the reaction comes out to be negative.

Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and [tex]\Delta H[/tex] for the reaction comes out to be positive.

[tex]HCl(aq)+NaOH(aq)\rightarrow KCl(aq)+H_2O(aq)[/tex] is an example of neutralization as acid and base combines to form salt and water and exothermic reaction as it releases heat in the reaction.

Average atomic mass of an element is a sum of the product of the isotope mass and its relative abundance.

For example: Chlorine has 2 isotopes with the following abundances

Cl(35): Atomic mass = 34.9688 amu; Abundance = 75.78%

Cl(37): Atomic mass = 36.9659 amu; Abundance = 24.22 %

Average atomic mass of Cl = 34.9688(0.7578) + 36.9659(0.2422) =

                                             = 26.4993 + 8.9531 = 35.4524 amu

Thus, the term “ average atomic mass “ is a weighted average so it is calculated differently from a normal average

The azimuthal quantum number (l) determines its orbital angular momentum and describes the shape of the orbital.

s-orbitals (for example 1s, 2s) are spherically symmetric around the nucleus of the atom.

p-orbitals are dumb-bell shaped. l = 0,1...n-1, when l = 1, that is p subshell.

d-orbitals are butterfly shaped.

hydrogen is not balanced

the right balanced equation is

Fe2O3 + 3 H2 -> 2Fe + 3H2O

Answer:1) Volume of [tex]AgNO_3[/tex] required is 55.98 mL.

2) 0.62577 grams of [tex]Ag_3PO_4[/tex] is produced.

Explanation:

[tex]3AgNO_3(aq)+Na_3PO_4(aq)\rightarrow Ag_3PO_4(s)+3NaNO_3(aq)[/tex]

1) Molarity of [tex]AgNO_3,M_1=0.225 M[/tex]

Volume of [tex]AgNO_3.V_1=?[/tex]

Molarity of [tex]Na_3PO_4,M_2=0.135 M[/tex]

Volume of [tex]Na_3PO_4,V_2=31.1 mL=0.0311 L[/tex]

[tex]Molarity=\frac{\text{number of moles}}{\text{volume of solution in liters}}[/tex]

[tex]\text{number of moles }Na_3PO_4=M_2\times V_2=0.135 mol/L\times 0.0311 L=0.0041985 moles[/tex]

According to reaction, 1 mole of [tex]Na_3PO_4[/tex] reacts with 3 mole of [tex]AgNO_3[/tex], then, 0.0041985 moles of [tex]Na_3PO_4[/tex] will react with:

[tex]\frac{3}{1}\times 0.0041985[/tex] moles of [tex]AgNO_3[/tex] that is 0.0125955 moles.

[tex]M_1=0.225 M=\frac{\text{number of moles of }AgNO_3}{V_1}[/tex]

[tex]V_1=\frac{0.0125955 moles}{0.225 M}=0.05598 L=55.98 mL[/tex]

Volume of [tex]AgNO_3[/tex] required is 55.98 mL.

2)

[tex]Molarity=0.195 M=\frac{\text{number of moles}}{\text{volume of solution in liters}}[/tex]

Number of moles of [tex]AgNO_3=0.195\times 0.023 L=0.004485 moles[/tex]

According to reaction, 3 moles of [tex]AgNO_3[/tex] gives 1 mole of [tex]Ag_3PO_4[/tex], then 0.004485 moles of [tex]AgNO_3[/tex] will give:[tex]\frac{1}{3}\times 0.004485[/tex] moles of [tex]Ag_3PO_4[/tex] that is 0.001495 moles.

Mass of [tex]Ag_3PO_4[/tex] =

Moles of [tex]Ag_3PO_4[/tex] × Molar Mass of [tex]Ag_3PO_4[/tex]

= 0.001495 moles × 418.58 g/mol = 0.62577 g

0.62577 grams of [tex]Ag_3PO_4[/tex] is produced.

Since it is round, and in the asteroid belt, he has most likely found a Dwarf planet. This is because it is round, so it might be round because of it's gravity.

Answer:

A. a new dwarf planet

Explanation:

it would come from your mom and dad

The definition of mechanical power is

                       Power = (work done) / (time to do the work).

From that definition, it looks pretty much like the power of a machine

depends on work and time.

Answer:

c. work and time

Explanation:

c is right on plato

Beryllium.

All four elements are found in the second column to the left of a periodic table. They are group 2 elements.

The 1st ionization energy generally decrease down each group.

Elements in each group have the same number of electrons in the outermost occupied electron shell. Electrons in the inner shell shield those in the outer shell from attractions from the nucleus, known as the shielding effect. The number of protons in each atom increase by more than 8 in each period. However, due to this effect, electrons in the outermost shell experience a far weaker force pulling them towards the center of the atom. For atoms of the four group 2 elements, electrons in the outermost layer would behave as if there's only two protons inside their nucleus. As a result, their end up with rather similar ionization energies.

Despite the same effective charge on each electron, the mean radius of the electrons increase down the group. Beryllium is in the second period; its electrons occupy only two electron shells in the ground state. On the contrary, strontium is in the fifth period; its electrons occupy up to five electrons shells in its ground state. The strength of electrostatic attraction decreases as the two charges move apart. As a result, outermost electrons in beryllium are way more attached to the nucleus than those in strontium.

FYI, the 1st ionization energy of the four elements are shown below:

The element with the highest first ionization energy among the choices is; Beryllium, Be

The ionization energy of an element is the energy required to remove one of the electrons in its outermost shell.

The first ionization energy of elements is inversely proportional to the atomic radii of elements.

This is so because a lesser atomic radius corresponds to greater electrostatic attraction between the electron and the nucleus of the atom.

We must also state that the atomic radius of elements in the periodic table increases down a group and decreases across a period.

In essence, the smaller the atom of an element, the larger is its first ionization energy.

The element with the highest first ionization energy is the smallest element and is therefore Beryllium, Be.

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1) Alkali metals - s block; one valence electron; lose one valence electron; charge of an ion +1.

Alkali metals have electronegativity from 0.7 to 1, lowest in Periodic table of elements, which means that alkali metals (I group in Periodic table) has positive oxidation number in compounds.

Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

For example, sodium (Na) is an element with atomic number 11 and it has one valence electron (3s¹) like all alkaline metals.

Electron configuration of sodium atom: ₁₁Na 1s² 2s² 2p⁶ 3s¹.

2) Alkaline earth metals - s block; two valence electrons; lose two electrons; charge of an ion is +2.

Beryllium, magnesium,calcium and strontium are alkaline earth metals. The elements have very similar properties. Alkaline earth metals have in common an outer s- electron shell (two electrons).

For example, atomic number of calcium is 20, it means that it has 20 protons and 20 electrons, so atom of calcium is neutral.

Electron configuration of calcium atom: ₂₀Ca 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²; calcium has two valence electrons (4s²).

3) Boron group - p block; three valence electrons; lose three electrons; charge of metal ions is +3; no nonmetals in this group; none.

For example, boron is an element with atomic number 5, which means it has 5 protons and 5 electrons, bcause atom has neutral charge.

Electron configuration of boron: ₅B: 1s² 2s² 2p¹, it has three valence electrons in 2s and 2p orbitals.

Atomic number is the number of protons, which is characteristic of a chemical element.

4) Carbon group - p block; four valence electrons; lose two or four electrons; charge of metal ions is +2 or +4; nonmetals gain four electrons; charge of nonmetals is -4.

Carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb) and flerovium (Fl) are in group 14 of Periodic table. They have same number of valence electrons (four) and similar chemical properties.

For example, carbon is a chemical element with symbol C and atomic number 6, which means it has 6 protons and six electrons. Valence electrons are in 2s and 2p orbitals.

Electron configuration of carbon atom: ₆C 1s² 2s² 2p².

5) Nitrogen group - p block;  five valence electrons; lose three or five electrons; charge of metal ions is +3 or +5; nonmetals gain three electrons; charge of nonmetals is -3.

Nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) and moscovium (Mc) are in group 15 of Periodic table. They have same number of valence electrons (five).

For example, bizmuth (Bi) has atomic number 83, it has 83 protons and 83 electrons. Valence electrons are in 6s and 6p orbitals.

Electron configuration of bizmuth atom: ₈₃Bi [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³.

6) Oxygen group - p block;  six valence electrons; lose four or six electrons; charge of metal ions is +4 or +6; nonmetals gain two electrons; charge of nonmetals is -2.

Oxygen (O), sulfur (S), selenium (Se), tellurium (Te) and the radioactive element polonium (Po) are in group 16 of Periodic table. They have same number of valence electrons (six).

For example, electron configuration of oxygen atom: ₈O 1s² 2s² 2p⁴.  

Oxygen atom has six valence electrons (2s² 2p⁴), so it is in 16 group of Periodic table of elements.  

7) Halogens - p block; seven valence electrons; nonmetals gain one electron; charge of nonmetals is -1.

Halogen elements are in group 17: fluorine (F), chlorine (Cl), bromine (Br) and iodine (I). They are very reactive and easily form many compounds.

Halogens need to gain one electron to have electron cofiguration like next to it noble gas.

For example, fluorine has 9 electrons and it gain easily one electron in chemical reaction to have electron configuration like noble gas neon (Ne) with 10 electrons.

Electron configuration of fluorine: ₉F 1s² 2s² 2p⁵.

8) Noble gases - p block; eight valence electrons (except helium with two valence electrons); do not gain or lose electrons; none.

Noble gases (group 18) are in group 18: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). They have very low chemical reactivity.  

Noble gases have very stable electron configuration and does not need to gain electrons, only when they gain energy .

Helium has atomic number 2, it has 2 protons and 2 electrons.

Electron configuration of helium atom: ₂He 1s².

Electron configuration of krypton atom:  

₃₆Kr 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶.

Answer:

A) X-rays

Step-by-step explanation:

Ultraviolet rays have a frequency range of 10¹⁵ Hz to 10¹⁷ Hz.

X-rays have a frequency range of 10¹⁷ Hz to 10²⁰ Hz, so they have a higher frequency than UV waves.

B) is wrong. The frequency range of infrared light is 10¹³ Hz to 4 × 10¹⁴ Hz.

C) is wrong. The frequency range of microwaves is 3 ×10¹¹ Hz to 10¹³ Hz.

D) is wrong. The frequency range of microwaves is 4 ×10¹⁴ Hz to 7.5 × 10¹⁴ Hz.

The X-rays has a frequency greater than ultraviolet waves.  

• The range of all the kinds of electromagnetic radiation is known as the electromagnetic spectrum.  

• The types of the electromagnetic waves, which makes up the electromagnetic spectrum are the visible light, microwaves, infrared light, UV rays, X-rays, and gamma rays.  

• The energy of the waves is directly proportional to its frequency and inversely proportional to their wavelengths.  

• The radiowaves exhibits the photons with least energies, followed by microwaves, infrared rays, visible, UV rays, X-rays, and the most energetic of all the waves is the gamma rays.  

• The wavelengths of the UV rays is smaller than infrared waves, microwaves, and visible light, however, it is greater than X-rays and gamma rays.  

• Thus, the frequencies of UV rays is more than the infrared waves, microwaves, and visible light, but is lesser than the frequencies of X-rays and gamma rays.  

Thus, of the mentioned options, X-rays will possess greater frequency than UV rays.  

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Answer:

5.15 L

Step-by-step explanation:

This looks like a case where we can use the Ideal Gas Law to calculate the volume.

pV = nRT       Divide both sides by p

 V = (nRT)/p

Data:

m = 7.25 g

R = 0.083 14 L·atm·K⁻¹mol⁻¹

T = (0 +273.15) K = 273.15K

p = 1 bar (Note: STP is 1 bar and 0°C)

Calculations:

(a) Moles of O₂

n = m/M

n = 7.25/32.00

n = 0.2266 mol

(b) Volume

V = (0.2266 × 0.083 14 × 273.15)/1

V = 161.3/2.00

V = 5.15 L  

The volume of 7.25 g oxygen gas at STP has been 5.075 L.

The oxygen has been assumed to be an ideal gas. The volume of 1 mole of an ideal gas at STP has been 22.4 L.

The moles of a gas has been given as:

[tex]\rm Moles=\dfrac{Mass}{Molar\;mass}[/tex]

The given mass of oxygen has been 7.25 g.

The molar mass of oxygen has been 32 g.

The moles of oxygen gas have been given as:

[tex]\rm Moles\;O_2=\dfrac{7.25}{32}\\Moles\;O_2= 0.226\;mol[/tex]

The moles of oxygen available has been 0.226 mol.

The volume of 0.226 mole oxygen at STP has been:

[tex]\rm 1\;mol=22.4\;L\\0.226\;mol=0.226\;\times\;22.4\;L\\0.226\;mol=5.075\;L[/tex]

The volume of 7.25 g oxygen gas at STP has been 5.075 L.

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 The  average mass  of nitrogen   is  14

         calculation

 step 1 :  multiply each percentage  by mass  number

 14 x 99.6  =1394

15 x 0.4 =   6

Step 2: add them up

 1394 + 6  = 1400

step 3: Then  divide by 100

= 1400/100 = 14

Answer:The average atomic mass of nitrogen is 14.004

Explanation:

Abundance of nitrogen-14 = 99.6 %

Fractional abundance[tex]=\frac{99.6}{100}=0.996[/tex]

Abundance of nitrogen-15 = 0.4 %

Fractional abundance[tex]=\frac{0.4}{100}=0.004[/tex]

Average atomic mass of an element =

[tex]\sum(\text{atomic mass of an isotopes}\times (\text{fractional abundance}))[/tex]

Average atomic mass of nitrogen =

[tex]14\times 0.996+15\times 0.004amu=14.004[/tex]

The approximate atomic mass of nitrogen is 14.004

Use the D = M/V equation, in which Density can be found by dividing Mass/Volume.

To solve, first find a rectangular prism tub that is filled to a certain level. Next, place the rock inside to find the amount of displacement (or how high the water level goes up.) In this way, you can find the volume of the rock.

Next, solve for the Mass. This can be found by dividing the total weight from the gravitational pull. This would give you the mass.

Finally, to find Density, divide the Mass found with the Volume. This would give you your final answer

~

The correct option is:

how elements arrange within a compound  

Structural formula are like models because they show how elements arrange within a compound.  

B. atoms must be electro negative.

Answer:

The answer is A.

Explanation:

This is a specific type of polar interaction that is established between two atoms with high electronegativity, usually between O or N, and an atom of H. In the case of oxygen, with a total of 8 electrons, two pairs of solitary electrons are presented and can act as acceptors of two hydrogen bridges. Nitrogen has one less electron and therefore has only one pair of solitary electrons to form a hydrogen bridge. These orbitals have a high negative charge density, and can, therefore, bind to the positive charge of hydrogen.

The interatomic distance between the hydrogen and the acceptor is less than the sum of its Van der Waals radius. The atomic radius of N and O are relatively small.

Have a nice day!

A pair of oxygen atoms can form an O2 molecule in which each atom has a total of eight valence electrons by sharing two pairs of electrons. The term covalent bond is used to describe the bonds in compounds that result from the sharing of one or more pairs of electrons.