Jill then wrote the formulas for all the possible compounds that sodium can form with the other ions. What formulas did she write?

Answer: it is easiest if you first find the percent of people present.  To do this, divide 1200/1500.  This equals 80%.  If there is 80% of students present, there needs to be 20% of students absent because it is out of 100% of students

Answer:

20%

Explanation:

Total number of students = 1500

Number of students present = 1200

Number of students absent = Total number of students - number of students present

Number of students absent = 1500 - 1200 =300

%number of students absent = 300 / 1500 * 100 = 20%

Answer:

Scientific knowledge can change because it is often examined and re-examined by new investigations and scientific argumentation but because of these frequent examinations, scientific knowledge becomes stronger, leading to its durability. Scientific knowledge is durable and robust, but open to change.

The importance of scientific knowledge changing lies in the fact that it represents the evolving nature of science, allowing us to deepen our understanding of the natural world, undergo paradigm shifts, and build cumulatively on previous knowledge.

It is important that scientific knowledge changes because science is a continuous, self-correcting process that develops our understanding of the natural world. Paradigm shifts, such as those identified by Thomas Kuhn, indicate radical changes in scientific thought that enable fresh understandings and advancements. For instance, rather than discarding Gregor Mendel's laws of inheritance upon learning how genes control traits, scientists expanded the framework, illustrating that knowledge is cumulative and subject to refinement as new discoveries emerge.

Debate and skepticism are inherent aspects of the scientific method and are crucial for validating and improving upon established ideas. This democratic nature ensures that the best data and theories prevail. Consequently, scientific progress is advanced as new findings are built upon the foundations laid by past research, allowing us to develop a larger, more accurate picture of our world and universe.

Furthermore, recognizing that scientific models are mental constructs subject to change, empowers us to remain flexible and receptive to new evidence while appreciating that some scientific knowledge can stand the test of time, providing continuity amid change.

Answer:

f = 80  flutter/ second

T= 0.0125 sec

Explanation:

Given data:

Fluttering of wings = 4800 time per minute

Frequency of wings = ?

Period for one wing in sec = ?

Solution:

There are 60 seconds in one minute, thus frequency of wings

4800/60 = 80  flutter per second

Period:

T = 1/f

T = 1/80

T= 0.0125 sec

Answer:

flutters per second is 80 and the period is 0.013.

Explanation:

i just took the test.

The length of a rectangle with a width of 4 inches and a length-to-width ratio of 3:2 is 6 inches.

If the ratio of the length of a rectangle to its width is 3 to 2, and if the width of the rectangle is 4 inches, we can set up a proportion to find the length. Using the ratio 3:2, we can write 3/2 = L/4, where L is the length of the rectangle we want to find. By cross-multiplying, we get 3 * 4 = 2 * L, which simplifies to 12 = 2L. Dividing both sides by 2, we find that L = 6 inches.

So, the length of the rectangle is 6 inches.

Answer:

15 g

Explanation:

Data given:

amount of  HF  = 153 mL  2.5 M HF

amount of Ca(OH)₂ = Excess

grams of CaF₂ = ?

Reaction Given:

                2HF + Ca(OH)₂ ------→ 2H₂O + CaF₂

Solution:

First we have to find number of moles of HF in 153 mL of 2.5 M HF

For this we will use following formula

               Molarity = moles of solute / liter of solution

Rearrange above equation

               moles of solute =  Molarity x liter of solution . . . . . (1)

Put values in above equation (1)

               moles of solute =  2.5 x 1 L

              moles of solute =  2.5

So,

we come to know that there are 2.5 moles of solute (HF) in 1 L of solution

Now how many moles of solute will be present in 153 ml of solution

Convert 153 mL to Liter

1000 mL = 1 L

153 mL = 153/1000 = 0.153 L

Apply Unity Formula

                       2.5 moles HF ≅ 1 L solution

                        X moles of HF ≅ 0.153 L solution

              moles of HF = 2.5 moles x 0.153 mL solution / 1 L solution

              moles of HF =  0.383 moles

Now Look at the reaction:

                     2HF + Ca(OH)₂ ------→ 2H₂O + CaF₂

                    2 mol                                          1 mol

From the reaction we come to know that 2 moles of HF gives 1 mole of CaF₂ then how many moles of CaF₂  will be produced from o.383 moles of HF

Apply Unity Formula

                       2 moles HF ≅ 1 mole of CaF₂

                       0.383 moles of HF ≅ X moles of CaF₂

              moles of CaF₂  = 0.383 moles x 1 mole / 2 mol

              moles of CaF₂ =  0.192 moles

Now we will find mass of 0.192 moles of  CaF₂

Formula will be used

          mass in grams = no. of moles x molar mass . . . . . . . (2)

molar mass of CaF₂ = 40 + 2(19)

molar mass of CaF₂ = 40 + 38 =  78 g/mol

Put values in eq. 2

        mass in grams = 0.192 x 78 g/mol

        mass in grams = 14.976 g

rounding the value

          mass in grams = 15 g

So,153 mL of 2.5 M HF is reacted with an excess of Ca(OH)₂ will produce 15 g of CaF₂.

Answer:

Ex1 = 4.3 moles

Explanation:

for Ex 1

 ** Number of mole = Mass (g) / Molecular weight ' Mw'  (g/mole)

for a = NaCl , first you must be calculate Mw = look to periodic table

Atomic weight for Na is 22.9 = 23 g and for Cl is 35.45 = 35 g

so Mw for NaCl = 23+35 = 58 g/mole

so Number of Moles for NaCl 250 g is

Number of Moles = 250 / 58 = 4.3 moles

do same for others ...

good luck ..

Answer:

Ex1. a) n NaCl = 4.277 mol NaCl

b) n KNO2 = 2.938 mol KNO2

c) n H2O2 = 7.349 mol H2O2

d) n KHSO3 = 2.080 mol KHSO3

Ex2. a) 2.31 E22 particles contained in 1.5 g K

b) 1.77 E22 particles contained in 0.470 g O

c) 2.332 E21 particles contained in 0.555 g AgCl

Ex3. molecules C2H5OH = 2.065 E24 molecules contained in 200 mL

Explanation:

Ex1.   n = mass (m) / molecular weight (Mw)

a) Mw NaCl = 22.989 + 35.453 = 58.442 g/mol

⇒ n NaCl = (250 g NaCl)/(58.442 g/mol) = 4.277 mol NaCl

b) Mw KNO2 = 39.0983 + 14.0067 + (2)15.9994 = 85.104 g/mol

⇒ n KNO2 = (250 g KNO2)/(85.104 g/mol) = 2.938 mol KNO2

c) Mw H2O2 = (2)(1.00794) + (2)15.9994 = 34.015 g/mol

⇒ n H2O2 = (250 g H2O)/(34.015 g/mol) = 7.349 mol H2O

d) Mw KHSO3 = 39.0983 + 1.00794 + 32.065 + 15.9994(3) = 120.169 g/mol

⇒ n KHSO3 = (250 g KHSO3)/(120.169 g/mol) = 2.080 mol KHSO3

Ex2.  n =  (m) / (Mw)

∴ 1 mol ≡ 6.022 E 23 particles

a) Mw K = 39.0983 g/mol

⇒  K = (1.5 g K)×(mol/39.0983 g K)×(6.022 E23 part/mol) = 2.31 E22 particles

b) Mw O = 15.9994 g/mol

⇒ O = (0.470 g O)×(mol/15.9994 g O)×(6.022 E23 part/mol) = 1.77 E22 part

c) Mw AgCl = 107.8682 + 35.453 = 143.32 g/mol AgCl

⇒ AgCl = (0.555 g)×(mol/143.32 g)×(6.022 E23 part/mol) = 2.332 E21 part.

Ex3. ethyl alcohol ( C2H5OH)

∴ δ C2H5OH = 0.79 g/mL

∴ V = 200 mL

⇒ molecules C2H5OH = ?

∴ Mw C2H5OH = (2)12.0107 + (5)1.00794 + 15.9994 + 1.00794 = 46.068 g/mol

⇒ molecules C2H5OH = (200 mL)×(0.79 g/mL)×(mol/46.068 g)×(6.022 E23 molecules/mol)

⇒ molecules C2H5OH = 2.065 E24 molecules C2H5OH

Answer: 0.5M

Explanation: see attachment for explanation. Thanks!

Final answer:

The molarity of a solution prepared by dissolving 10.0 g of NaOH in 500.0 mL of solution is 0.500 M.

Explanation:

To calculate the molarity of a solution, we need to know the amount of solute in moles and the volume of the solution in liters. The question provides the mass of sodium hydroxide (NaOH) and the volume of the solution.

Solution
Before we start, we must convert the given mass of NaOH to moles using its molar mass, which is 40.00 g/mol:

10.0 g NaOH × (1 mol NaOH / 40.00 g NaOH) = 0.250 mol NaOH

Convert the volume of solution from milliliters to liters:

500.0 mL × (1 L / 1000 mL) = 0.500 L

Use the definition of molarity (M):

Molarity (M) = moles of solute / liters of solution

M = 0.250 mol / 0.500 L = 0.500 M

Answer:

1. A molecule

2. A mixture

3. Concentration

4. Chemical formula

5. Kinetic energy

Explanation:

1. A molecule consists of two or more different types of atoms bonded together.

For this question, it's important to understand that we cannot be too abstract and use terms, such as compound. The reason is simple: molecules consist of atoms, and while molecules produce compounds, the latter can also be ionic. Ionic compounds would contain ions in them rather than atoms. In ionic compounds, electrons are transferred from one atom to the other to form cations and anions.

Molecules, on the other hand, consist of atoms. In fact, those atoms shouldn't necessarily be different: for example, we may have an oxygen gas molecule which consists of two oxygen atoms.

2. A mixture is a combination of different substances that can be separated by physical means.

Usually, mixtures are in the same physical state, for example, we may have a mixture of an aqueous layer, such as water, and an organic layer, such as hexane. In order to separate them, we might use a separation funnel, as water is polar and hexane is non-polar, they will form two separate layers. Collecting the bottom layer in a separate flask from the funnel and then the remaining layer will help us separate them based on their difference in polarity.

3. Many variables in chemistry depend on the amount of water present. Water is a solvent. One of the typical examples is concentration. Concentration, or molarity, is a ratio between the moles of a solute and the volume of a solution. Changing the amount of water would change the concentration of a solute as a result.

E. g., if we evaporate water, our solvent, from a specific solution, the concentration of a solute will increase, as we'll have the same amount of a solute in moles for a lower volume of a solution. Similarly, if we dilute the solution (increase the volume of it by adding more water), the volume will increase and we'll have the same amount in moles of the solute for a greater amount of the solution, so the concentration will decrease.

4. A chemical formula has fixed definite proportions at all times. Regardless of what mass of a compound we have, according to the law of definite proportions, atoms always combine in a fixed ratio in compounds. For example, we know that we would always have two hydrogen atoms and one oxygen atom in a water molecule regardless of what mass of water we have.

Similarly, if we remember ionic compounds, if we take sodium chloride, NaCl, the ionic ratio between sodium and chloride ions is always 1 : 1 (one sodium cation combined with one chloride anion). This is fundamentally true and it's independent of any quantity.

5. Similarly, this is an open question. A typical answer to this would be kinetic energy. Kinetic energy only depends on temperature of a substance. Kinetic energy is the energy of movement: the greater it is, the greater the velocity of an object.

The greater the temperature, the higher the kinetic energy. This direct proportionality is seen from the equation [tex]E_k = \frac{3}{2} kT[/tex], where k is a constant and T is the absolute temperature. Notice that for higher T values, the kinetic energy term is higher.

Thinking about it from the other perspective, density, as another example, also depends on temperature. The greater the temperature, the greater the distances between the molecules, so the density decreases with an increase in temperature.

There are many more thermodynamic examples to look at as well!

Answer: By atomic number

Answer:

According to the atomic number or number of proton

Explanation:

Answer:

D)All of the above

Explanation:

Answer:

I don't have the number of cubes in each bag, but whichever bag had the most cubes would have the most kinetic energy as it falls

Answer:

Air in a refrigeration system causes  All of the above problems.

Explanation:

The acid build up is basically seen when the circuit system comes in contact with air, moisture, more heat, various contaminants and also various impurities which enhances the chemical reaction helps in making of acid. Moisture is found when the warm air comes in contact with the cooling system inside the refrigerator. It basically occurs if the defrost condition not working properly.  Copper plating is the compressors metal parts that has been coated with the copper when this comes in contact with air leads to corrosion.

Answer:

238

Explanation:

To find the atomic mass, you add protons and neutrons

Number of Protons‎: ‎92

Number of Neutrons‎: ‎146

146+92=238

Answer:

The percent yield is 42.52%.

Explanation:

Theoretical yield of beryllium chloride = 12.7 g

Actual yield of the beryllium chloride = 5.4 g

The formula used for the percent yield will be :

[tex]\text{Percent yield}=\frac{\text{Actual yield}}{\text{Theoretical yield}}\times 100[/tex]

Now put all the given values in this formula, we get:

[tex]\%(yield)=\frac{5.4 g}{12.7 g}\times 100=42.52\%[/tex]

The percent yield is 42.52%.

Answer & Explanation:

Take, for example, an apple tree. ... When an apple falls from the tree to the ground, its energy of position (stored as gravitational potential energy) is converted to kinetic energy, the energy of motion, as it falls. When the apple hits the ground, kinetic energy is transformed into heat energy.

Answer: proton

Explanation:

Answer:

repelled

Explanation:

like charges repel one another

The correct order for the first three steps of the scientific method is:D. State the question, form a hypothesis, conduct an experiment.

Here is a step-by-step explanation:

1. State the question: This is the first step in the scientific method. It involves identifying a problem or question that you want to investigate. It is important to clearly define the question you want to answer through your experiment.

2. Form a hypothesis: After stating the question, you need to come up with a hypothesis. A hypothesis is an educated guess or prediction that explains the relationship between the variables being studied. It is usually stated as an "if-then" statement, where you propose that if a certain condition is met, then a specific outcome will occur.

3. Conduct an experiment: Once you have a hypothesis, you can design and carry out an experiment to test it. An experiment involves systematically manipulating and controlling variables to observe their effects and gather data. It is important to carefully plan and conduct the experiment to ensure reliable and valid results.

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Answer:

2 atoms leftb

Explanation:

Answer:

The number of chlorine atoms present in [tex]6.02 \times 10^{23}[/tex] units of gold III chloride is [tex]18.066 \times 10^{23}[/tex]

Explanation:

Formula of Gold (III) chloride: [tex]AuCl_{3}[/tex]

Avogadro Number : Number of particles present in one mole of a substance.

[tex]{N_{0}} =6.022 \times 10^{23}[/tex]

Using,

[tex]n(moles)=\frac{Given\ number\ of\ particles}{N_{0}}[/tex]

[tex]n =\frac{6.02\times 10^{23}}{6.022\times 10^{23}}[/tex]

= 1 mole(0.9999 , nearly equal to 1 )

The given Gold III chloride sample is 1 mole in amount.

[tex]6.022 \times 10^{23}[/tex]  = 1 mole of [tex]AuCl_{3}[/tex]

In this Sample,

1 mole of [tex]AuCl_{3}[/tex] will give = 3 mole of Chlorine atoms

1 mole of Cl contain = [tex]6.022 \times 10^{23}[/tex]

3 mole of Cl contain = [tex]6.022 \times 10^{23}\times 3[/tex]

3 mole of Cl contain =[tex]18.066 \times 10^{23}[/tex]

So,

The number of chlorine atoms present in [tex]6.02 \times 10^{23}[/tex] units of gold III chloride is [tex]18.066 \times 10^{23}[/tex]

Answer:

Explanation:

Did you know? An ecosystem is defined as any community of living and non-living things that work together. Ecosystems do not have clear boundaries, and it may be difficult to see where one ecosystem ends and another begins. In order to understand what makes each ecosystem unique, we need to look at the biotic and abiotic factors within them. Biotic factors are all of the living organisms within an ecosystem. These may be plants, animals, fungi, and any other living things. Abiotic factors are all of the non-living things in an ecosystem.

Help this answer can help you :)

Sunlight, climate, soil, water, and air are the abiotic factors. Therefore, option D is correct.

Abiotic components, also known as abiotic factors, are non-living chemical and physical elements of the environment that have an impact on living organisms and the functioning of ecosystems. Biology is supported by abiotic factors and the phenomena associated with them.

Abiotic factors include sunlight, air, precipitation, minerals, and soil. These variables have a significant impact on species survival and reproduction in an ecosystem.

An abiotic factor is a non-living component of an ecosystem that influences its surroundings. Temperature, light, and water are some examples in a terrestrial ecosystem. Abiotic factors in a marine ecosystem include salinity and ocean currents.

Thus, option D is correct.

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Answer:

D or B

Explanation:

Waves break by shorelines so height will decrease. I dont know about wave speed so i put two answers

As a water wave nears the coastline, the wave height increases and the wave speed decreases due to friction with the seafloor, a process called shoaling, which ultimately leads to the waves breaking on the shore.

As a water wave nears the coastline, its behavior changes due to the decreasing water depth. As the wave approaches shallow water, its wave speed decreases because it starts to feel the ocean bottom. When the depth becomes less than about half the wave's wavelength, the bottom part of the wave experiences friction and slows down, causing the wave to steepen. This is accompanied by a decrease in wavelength and an increase in wave height, a process known as shoaling. Eventually, this leads to the wave breaking when the wave steepness reaches a certain limit; commonly, this limit is when the wave height is one-seventh the wavelength.

Answer:

Changing direction is an example of a kind of acceleration

Explanation:

Acceleration is the "change of velocity" of an object concerning time. Acceleration being vector quantities, thus an object’s acceleration is the produce of orientation of the net force that has been acted on the object.  

Newton’s second law explains the magnitude of acceleration. An example is when a car travels in the straight line, it is accelerates in the direction of its travel. As the car turns the acceleration occurs in a new direction.  

Changing direction refers to acceleration, because it's about the change in velocity, which includes both speed and direction. So, if the direction changes but speed remains the same, there is still acceleration.

Changing direction is an example of a kind of acceleration. Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity.

This is seen when an object changes its speed, direction, or both. For example, if you are driving a car and make a turn, even if your speed remains constant, you're experiencing acceleration because your direction is changing. Therefore, changing direction is associated with acceleration, not speed, velocity, or a constant rate.

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Answer:

The pattern of decay emission is visualized on X-ray film by auto-radiography.

Explanation:

The image on the x-ray are auto-radiography or the nuclear emission that has been produced as a result of the decay emission because of the gamma particles or the beta particles which comes from a radioactive substance.  These auto-radiography are available as the digital image as a result of recent development of gas detectors or because of the rare earth phosphor imaging system. Some of the can be studied microscopically for silver granules this method is called as micro- auto-radiography.

Answer: the pattern of hybridization

Explanation:

did it

Answer:

[tex]2s^2 2p^2[/tex]

Explanation:

Group 4A contains a total of 4 electrons for each atom in their valence shell. Filling the orbital diagram, let's say, for carbon, notice that when we start with period 2, we have two elements in the s-block, that is, lithium and beryllium. They correspond to the two s electrons that belong to the valence shell of carbon.

Moving on, we have boron and carbon, the remaining 2 electrons. Now, starting with boron, we're in the p-block.

That said, looking at the second period, the electron configuration for the valence shell of a group 4A element would be:

[tex]2s^2 2p^2[/tex]

Final answer:

At equilibrium, the forward reaction rate equals the reverse reaction rate, indicating a dynamic balance where the concentrations of reactants and products remain constant.So,option d. The forward reaction rate is equal to the reverse reaction rate is correct.

Explanation:

When a reaction is at equilibrium, the forward reaction rate is equal to the reverse reaction rate. This state is achieved when the rate of the forward reaction decreases and becomes constant while, simultaneously, the rate of the reverse reaction increases and becomes constant, reaching a point where both rates are equal. This equilibrium indicates that the concentrations of reactants and products remain constant over time, illustrating a dynamic balance between the forward and reverse processes.

To prepare a 0.5 M sucrose solution with a volume of 600 cm³, you would need to dissolve 102.6 grams of sucrose.

How to Calculate the Mass of Sucrose for a Semi Molar Solution

To prepare a semi molar solution, you first need to understand that "semi molar" implies a 0.5 molar concentration of the solute. Given that the molecular mass of sucrose is 342 g/mol, we can proceed with the calculations.

To prepare a 0.5 M solution, 0.5 moles of sucrose per liter of solution are needed. Since the density of a sucrose solution is not provided, we will assume the density of water for this example, which is 1 g/cm³, making 600 cm³ of solution equivalent to 600 mL or 0.6 L.

Now, we calculate the number of moles of sucrose required as follows:

Finally, to find the mass of sucrose:

Therefore, to prepare a semi molar (0.5 M) solution, you would need to dissolve 102.6 grams of sucrose in 600 cm³ of solution.

Final answer:

To make a 0.5 M sucrose solution with a volume of 600 cm³, 102.6 grams of sucrose, which has a molar mass of 342, must be dissolved.

Explanation:

The question is about finding the mass of sucrose needed to prepare a semi molar solution, assuming semi molar refers to 0.5 M (molar concentration). Since the molecular mass of sucrose is given as 342, to prepare 600 cm³ (which is equivalent to 0.6 L) of a 0.5 M solution, the number of moles needed will be 0.5 moles/L × 0.6 L = 0.3 moles of sucrose. To find the mass of sucrose, we will multiply the number of moles by the molar mass:

Mass of sucrose = Number of moles × Molar mass
= 0.3 moles × 342 g/mole
= 102.6 g

Therefore, to prepare the desired semi molar solution, 102.6 grams of sucrose should be dissolved in 600 cm³ of solution.

Answer: 1.D

2. A

3. D

Explanation:

Answer:

Low energy waves have a long wavelength.

Explanation:

Energy of wave is directly related to  the frequency while it is inversely proportional to the wavelength.

If any wave have high energy it will have high frequency and smaller wavelength.

If the wave have lower energy then it will have lower frequency and higher wavelength.

Mathematical relationship:

E = h. f

E = h. c/λ

E= energy

h = planck's constant

f = frequency

c = speed of light

λ = wavelength