Q: Which of the following is the correct formula for calculating molarity?

$$\text{Molarity} = \frac{\text{moles of solute}}{\text{volume of solution in L}}$$

Q: Which of the following is the correct formula for calculating percent by mass/volume?

$$\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}} \times 100\%$$

Question 1

A student needs to prepare 250.0 mL of a 0.500 M NaCl solution. What mass of NaCl (in grams) should be used? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$7.31 g$$

Question 2

Which of the following best describes the empirical formula for a compound with 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 3

A hydrate of magnesium sulfate has a mass of 5.00 g before heating and 2.44 g after heating. What is the percent by mass of water lost?

Accepted Answer

$$51.2\%$$

Question 4

How many moles are present in 15.0 g of sodium bicarbonate (NaHCO$$_3$$)? (Molar mass = 84.01 g/mol)

Accepted Answer

$$0.179$$ mol

Question 5

A solution is prepared by dissolving 7.5 g of KCl in enough water to make 500 mL of solution. What is the percent by mass/volume of KCl in the solution?

Accepted Answer

$$1.0\%$$

Question 6

Which of the following statements about solubility curves is correct?

Accepted Answer

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

Question 7

A 2.00 L solution of NaNO$$_3$$ has a concentration of 1.50 M. How many moles of NaNO$$_3$$ are present?

Accepted Answer

$$3.00$$ mol

Question 8

A gold coin contains $$3.01 	imes 10$$^{22}$$ atoms of gold. How many moles of gold does the coin contain?

Accepted Answer

$$0.050$$ mol

Question 9

A solution is diluted from 2.00 M to 0.500 M. If the initial volume was 100.0 mL, what is the final volume after dilution?

Accepted Answer

$$400.0 mL$$

Question 10

A compound is found to contain 58.8% copper and 41.2% oxygen by mass. What is the empirical formula?

Accepted Answer

$$\mathrm{CuO}$$

Question 11

A sample of calcium chloride dihydrate (CaCl$$_2$$·2H$$_2O) is $$heated and loses 2.16 g of water, leaving 3.00 g of anhydrous CaCl$$_2. $$What is the percent by mass of water in the hydrate?

Accepted Answer

$$41.9\%$$

Question 12

Which of the following is the correct formula for calculating molarity?

Accepted Answer

$$	ext{Molarity} = \frac{	ext{moles of solute}}{	ext{volume of solution in L}}$$

Question 13

If 5.00 g of NaOH is dissolved in enough water to make 250.0 mL of solution, what is the molarity of the solution? (Molar mass = 40.00 g/mol)

Accepted Answer

$$0.500 M$$

Question 14

A solution is prepared by diluting 50.0 mL of 6.00 M HCl to a final volume of 300.0 mL. What is the final concentration?

Accepted Answer

$$1.00 M$$

Question 15

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more solute than can theoretically dissolve at a given temperature.

Question 16

A sample of gas has a volume of 75.0 L at STP. How many moles of gas are present? (1 mol = 22.4 L at STP)

Accepted Answer

$$3.35$$ mol

Question 17

A compound has an empirical formula of CH$$_2O $$and a molar mass of 180 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$

Question 18

Which of the following is the correct formula for calculating percent by mass/volume?

Accepted Answer

$$\frac{	ext{mass of solute (g)}}{	ext{volume of solution (mL)}} 	imes 100\%$$

Question 19

A solution is made by dissolving 10.0 g of NaCl in enough water to make 200.0 mL of solution. What is the percent by mass/volume of NaCl?

Accepted Answer

$$5.0\%$$

Question 20

A hydrate sample of CaSO$$_4$$·xH$$_2O $$has a mass of 6.16 g before heating and 4.34 g after heating. What is the value of x in the hydrate? (Molar mass of CaSO$$_4 = 136.14 g/$$mol, H$$_2O = 18.02 g/$$mol)

Accepted Answer

$$2$$

Comprehensive Study Guide for General Chemistry: Moles, Formulas, Solutions, and Solubility

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