Chapter 3 Pt 2 Molarity and Dilutions

A 0.70 M solution contains 3.0 g of potassium chlorate (KClO3). What is the volume of the solution?

Correct answer: 0.035 L Volume (L)=mole solute/molarity (M) First, calculate the moles of solute in the solution using the given mass and molar mass.3.0 g122.548 gmol=0.024 moles/Second, use your calculated moles and given molarity to calculate volume.Volume (L)=0.024 moles/0.70 M=0.035 L

A solution of NiCl2 with a volume of 50 mL and concentration of 0.10 M is diluted to a volume of 0.10 L. What is the concentration of the resulting solution? Select the correct answer below: 5.0 M 0.05 M 50 M 0.50 M

Correct answer: 0.05 M The dilution equation is C1V1=C2V2 so we find: (0.10 M)(0.05 L)=(x)(0.10 L) Solving for x, we find x=0.05 M.

A solution has a concentration of 0.8 M and contains 15 g AgBrO3. What is the volume of the solution? Select the correct answer below: 0.02 L 0.05 L 0.07 L 0.08 L

Correct answer: 0.08 L First, you have to calculate the molar mass for AgBrO3. This is 235.769 g/mol. Second, you have to calculate the number of moles in the sample by dividing the given mass by the molar mass. 15 g235.769 g/mol=0.064 moles Then, you can divide the calculated moles by the given concentration. 0.064 moles0.8 M=0.08 L Your answer:

A 0.15 M NaOH solution has a volume of 0.125 L but is then diluted to 0.15 L. What is the concentration of the new solution? Select the correct answer below: 0.08 M 0.113 M 0.142 M 0.125 M

Correct answer: 0.125 M The dilution equation is C1V1=C2V2 so we find: (0.15 M)(0.125 L)=(x)(0.15 L) Solving for x, we find x=0.125 M.

A 0.125 M solution contains 5.3 g Na2CO3. What is the volume of the solution?

Correct answer: 0.40 L First, find the number of moles of Na2CO3 using the formula mass of 105.98gmol from the periodic table: 5.3g×1mol105.98g=0.050mol Next, rearrange the definition of molarity to find the volume from the molarity and the concentration: molarity (M)=moles of solute/volume of solution (L) volume of solution (L)=moles of solute/molarity=0.050mol 0.125molL=0.40L

A solution is made by adding 120 g of citric acid to 210 g of water. What is the percent mass of citric acid in this solution? Select the correct answer below: 57.1% 36.4% 27.3% 13.3%

Correct answer: 36.4% mass percentage=mass solutemass solution×100%mass solution=120 g+210 g=330 gmass percentage=120 g330 g×100=36.4%

Calculate the volume of a solution prepared by diluting a 2.0 L solution of 0.80 M Ca(CO3)2 to 0.30 M . Select the correct answer below: 5.3 L 6.1 L 6.7 L 7.2 L

Correct answer: 5.3 L The dilution equation is: C1V1=C2V2(0.80 M)(2.0 L)=(0.30 M)(x)x=5.3 L

When calculating the concentration of a diluted solution using the equation M1V1=M2V2 (also sometimes given as c1V1=c2V2), what must be true about the units of volume? Select the correct answer below: V1 and V2 can be any volume units, as long as they are the same. V1 and V2 must both be expressed in liters. V1 and V2 must both be expressed in milliliters. The volume of the more concentrated mixture, V1, must be expressed in milliliters, while the more dilute volume, V2, must be expressed in liters.

Correct answer: V1 and V2 can be any volume units, as long as they are the same. The dilution equation can be used with any volume units as long as they are the same on both sides. Although molarity is defined as moles per liter, the products M1V1 and M2V2 need not have units of moles as long as they have the same dimensionality.

Which of the following will decrease the concentration of a solution? Select all that apply. Select all that apply: adding more solute adding more solvent removing moles of solute removing solvent by evaporation

Correct answer: adding more solvent removing moles of solute We can decrease the concentration of a solution by 1) adding more solvent, and 2) decreasing the number of moles of solute. This second option is often impractical or difficult to accomplish, so when we decrease a solution's concentration, it is typically by dilution.

Which of the following stays constant when diluting a solution? Select the correct answer below: volume molarity concentration amount of solute

Correct answer: amount of solute The amount of solute in a solution is unaffected by dilution. The addition of solvent to a solution will change the solution concentration (in molarity and in all other units) and the solution volume, but the moles of solute remains constant.

When diluting a solution, which of the following changes? Select all that apply. Select all that apply: solution volume solution concentration moles of solute liters of solvent

Correct answer: solution volume solution concentration liters of solvent Dilution is the addition of solvent to a solution. More solvent means more volume, and more solvent means the concentration of solute will be reduced. So, the solution volume will increase, the solution concentration (meaning the concentration of solute) will decrease, and the liters of solvent will increase. Notice that no solute is added in a dilution, so the number of moles of solute in the solution will not change.

What is the volume of a solution with a concentration of 2.90 M and containing 15.0 g BaCl2? Your answer should have three significant figures.

Correct answers: 0.0248 L​ First, you have to calculate the molar mass for BaCl2. This is 208.234 g. Now, calculate the number of moles in the sample by dividing the given mass by the molar mass. 15.0 g208.234 g/mol=0.07203 moles Then, you can divide that calculated moles by the given concentration. 0.07203 moles2.90 M=0.02484 L Therefore, after rounding to three significant figures, we find that the volume of the solution is 0.0248L.

A solution has a concentration of 0.56 M KBr and a volume of 0.04 L. It is then diluted to a concentration of 0.28 M. What is the new volume? Your answer should have one significant figure.

Correct answers: 0.08 L​ The dilution equation is: C1V1=C2V2 so we find(0.56 M)(0.04 L)=(0.28 M)(x)x=0.08 L

A solution has a concentration of 0.6 M KOH and a volume of 0.04 L. It is then diluted to a concentration of 0.3 M. What is the new volume, in liters? Your answer should have one significant figure.

Correct answers: 0.08 L​ The dilution equation is: C1V1=C2V2(0.6 M)(0.04 L)=(0.3 M)(x)x=0.08 L

156 g C12H22O11 (sucrose) is dissolved into 4.0 L of solution. What is the molar concentration of the solution? Report your answer with the correct number of significant figures.

Correct answers: 0.11 M​ M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and the molar mass. 156 g/342.297 g/mol=0.456 molThen, you can solve for molarity using the molarity equation and round to two significant figures.M=0.456 mol/4.0 L=0.11M

A solution has a concentration of 3.0 M and a volume of 0.20 L. If the solution is diluted to 4.0 L, what is the new concentration, in molarity? Your answer should have two significant figures.

Correct answers: 0.15 M​ The dilution equation is C1V1=C2V2(3.0 M)(0.20 L)=(x)(4.0 L)x=0.15 M

Calculate the concentration of a solution prepared by diluting 0.058 L of 0.28 M SiF6 solution to a volume of 0.075 L. Your answer should have two significant figures.

Correct answers: 0.22 M​ The dilution equation is C1V1=C2V2(0.28 M)(0.058 L)=(x)(0.075 L)x≈0.2165 M Rounding to two significant figures, the concentration of the solution is 0.22 M.

15 g NiO is dissolved into enough water to make 800. mL of solution. What is the molar concentration of the solution? Report your answer with the correct number of significant figures.

Correct answers: 0.25 M​ M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and the molar mass. 15g/74.692 g/mol≈0.20 molThen, you can solve for molarity using the molarity equation. The answer should be reported to two significant figures.M=0.20 mol 0.800 L=0.25 M

A 0.10 L solution with 1.85 g of Ca(OH)2 is of what concentration, in molarity? Your answer should have two significant figures.

Correct answers: 0.25 M​ First, convert grams to moles using the formula mass of 74.094gmol for Ca(OH)2 from the periodic table. 1.85g×1mol74.094g=0.02497mol Next, divide by the volume to find the molarity. M=0.02497mol0.10L=0.2497molL Finally, round to the correct number of significant figures (in this case, two): 0.25M.

A 0.20 M solution contains 6.4 g of SO2. What is the volume of the solution? Report your answer with two significant figures.

Correct answers: 0.50 L​ Volume (L)=moles solute/molarity (M) First, calculate the moles of solute in the solution using the given mass and molar mass.6.4 g/64.064 g/mol=0.10 moles/Second, use your calculated moles and given molarity to calculate volume.Volume (L)=0.10 moles/0.20 M=0.50 L

A 2.5 L solution with 100. g Na2S has a molarity of: Your answer should have two significant figures.

Correct answers: 0.51 M​ M=mol solute L solution First, calculate the number of moles by dividing the given mass by the molar mass:100 g78.045 g/mol=1.28 molesSecond, calculate molarity using moles of solute and the given volume: 1.28 moles2.5 L=0.51 M

A 2.5 M solution of KBr has a volume of 0.10 L. If the solution is diluted to 0.45 L, what is the new concentration? Your answer should have two significant figures.

Correct answers: 0.56 M​ The dilution equation is C1V1=C2V2. Substitute in the known values and rearrange to solve for the concentration. (2.5 M)(0.10 L)=(C2)(0.45 L) C2=(2.5 M)(0.10 L)0.45 L=0.5555 M The answer should have two significant figures, so round to 0.56 M.

What is the molar concentration of a 300.0 mL solution containing 5.00 g of NH3?

Correct answers: 0.979 M​ First, calculate the number of moles by dividing the given mass by the molar mass: 5.00g/17.031 g/mol=0.2936mol Second, calculate molar concentration by dividing the moles of solute by the given volume. Remember to convert the given volume from milliliters to liters. The given volume, 300.0mL, is equal to 0.3000L.0.2936mol0.3000L=0.978 M Therefore, after rounding to three significant figures, we find that the molar concentration is about 0.979M.

A solution of 3.51 M NiCl2, has a volume of 4.57 L. If the solution is diluted to 12.5 L, what is the new concentration? Your answer should have three significant figures.

Correct answers: 1.28 M​ The dilution equation is C1V1=C2V2(3.51 M)(4.57 L)=(x)(12.5 L)x=1.28 M

A solution has a concentration of 18.1 M and contains 2.45 g of H2SO4. What is the volume of this solution in milliliters? Your answer should have three significant figures.

Correct answers: 1.38 mL​ First determine the amount of H2SO4 in 2.45g. 2.45gH2SO4×1mol98.078g=0.02498mol Now, use the concentration of H2SO4 to determine the volume of the solution.0.02498mol×1L18.1 mol=0.0013801L=1.3801mL Rounding the three significant figures, the volume of the solution is 1.38mL.

What is the mass percentage of 38.2 g of calamine in a 349 g solution? Your answer should have three significant figures.

Correct answers: 10.9%​ To determine the mass percentage, divide the fraction of mass by the total mass and multiply by 100. mass percentage=mass solute/mass solution×100%mass percentage=38.2 g349 g×100=10.9%

How many grams of H2SO4 would be needed to make a 2.00M solution with a volume of 0.750L?

Correct answers: 147 g​ Recall that the units for molarity (M) are molL. By dimensional analysis, we can see that we can calculate the number of moles of solute required by multiplying the concentration by the liters of solution. 0.750L×2.00M=1.50mol Next, convert from moles to grams, using the molar mass of H2SO4 from the periodic table: 1.50mol×98.078gmol=147.12g Finally, round to the correct number of significant figures (in this case, three): 147g.

If 110. grams of potassium carbonate (K2CO3) is dissolved into 300. mL of solution, what is the molarity of the solution?

Correct answers: 2.65 M​ M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and the molar mass.110 g138.204 g/mol≈0.7959 molThen, you can solve for molarity using the molarity equation. Note that 300. mL is 0.300 L.M=0.7959 mol0.300 L=2.653 M The answer should have three significant figures, so round to 2.65 M. Remember, you need to convert mL to L before you can calculate molarity.

734 g of Li2SO4 is dissolved in a 2510 mL solution. What is the concentration of the solution? Report your answer with the correct number of significant figures.

Correct answers: 2.66 M​ The molecular mass of Li2SO4 is 109.94 g/mol Calculate moles: 734 g/109.94 g/mol=6.68 mol Calculate molarity: M=6.68/mol2.51 L=2.66 M

What is the percent mass of potassium chloride in a solution made by adding 25 g of potassium chloride to 70.0 ml of water? Your answer should have two significant figures.

Correct answers: 26%​ The density of water is 1gmL, so 70.0 mL of water is equal to 70.0 g of water. Write the equation for the mass percent of solute in the solution. mass percentage=mass solute/mass solution×100% Add the mass of potassium chloride to the mass of water to calculate the total mass of the solution. mass solution=25 g+70.0 g=95 g Now, substitute the mass of solute and the total mass of the solution into the original equation to calculate the mass percent of potassium chloride. mass percentage=25 g95 g×100%=26.3% Therefore, after rounding to two significant figures, we find that the mass percent of potassium chloride is approximately equal to 26%.

How many grams of H2SO4 must be dissolved in 1.08 L of solution to generate a solution with a concentration of 2.69 M? Your answer should have three significant figures.

Correct answers: 285 g​ 2.69 M=x1.08 Lx=2.9052 moles2.9052 moles×98.078 g/mol≈285 g

Calculate the volume, in milliliters, of a solution prepared by diluting a 3.55 M solution with a volume of 6.929 mL to 0.823 M. Your answer should have three significant figures.

Correct answers: 29.9 mL​ The dilution equation is: C1V1=C2V2 Solving for V2 (3.55 M)(6.929 mL)=(0.823 M)(x)x=29.9 mL

What is the molarity of a solution if there are 160.0 g of H2SO4 in a 0.500 L solution? Your answer should have three significant figures.

Correct answers: 3.26 M​ M=mol solute L solution First, calculate the number of moles by dividing the given mass by the molar mass:160.0 g98.078 g/mol=1.631 molesSecond, calculate molarity using moles of solute and the given volume: 1.631 moles0.500 L≈3.26 M

A 4.50 mL solution has a concentration of 12 M. What mass of TiO2 must be present in solution? Your answer should have two significant figures.

Correct answers: 4.3 g​ First, convert mL to L by dividing by 1000. 4.50 mL1000=0.0045 L Second, multiply volume by concentration to get the moles of solute. 0.0045L×12 M=0.054 moles Third, convert moles to grams using the molar mass. 0.054 moles×79.866 g/mol=4.3 g

How many grams of AgCl would be needed to make a 4.0 M solution with a volume of 0.75 L? Your answer should have two significant figures.

Correct answers: 430 g​ Recall that the units for molarity (M) are molL. By dimensional analysis, we can see that we can calculate the number of moles of solute required by multiplying the concentration by the liters of solution. 0.75L×4.0M=3.0mol Next, convert from moles to grams, using the molar mass of AgCl from the periodic table: 3.0mol×143.321gmol=429.963g Finally, round to the correct number of significant figures (in this case, two): 430g.

What is the volume of a solution, in milliliters, that contains 1.5 g LiNO3 and has a concentration of 0.40 M? Your answer should have two significant figures.

Correct answers: 54 mL​ First, you have to calculate the molar mass for LiNO3. This is 68.944 g/mol. Second, you have to calculate the number of moles in the sample by dividing the given mass by the molar mass. 1.5 g68.944 g/mol=0.02176 moles Then, you can divide the calculated moles by the given concentration. 0.02176 moles 0.40 M=0.0544 L Then you need to multiply 0.0544 by 1000 to get mL, which gives us 54.4 mL. Rounding to two significant figures gives 54 mL.

A solution is made by adding 5.01 g of iron sulfate to 75.3 g of water. What is the mass percentage of iron sulfate in this solution? Your answer should have three significant figures.

Correct answers: 6.24%​ To determine the mass percentage, divide the fraction of mass by the total mass and multiply by 100. mass percentage=mass solute/mass solution×100mass solution=5.01 g+75.3 g=80.31 gmass percentage=5.01 g80.31 g×100=6.24%

What is the volume (in milliliters) of a 4.0 M solution containing 3.06 g of H2SO4?

Correct answers:7.8 mL​ Volume (L)=moles solute/molarity (M) First, calculate the moles of solute in the solution using the given mass and molar mass.3.06/ g98.078gmol=0.03120 molesSecond, use your calculated moles and given molarity to calculate volume.Volume (L)=0.03120 moles 4.0molesL≈0.007800 L Converting to milliliters and rounding to two significant figures gives a volume of 7.8 mL.