Q: Which of the following best defines molarity ($M$) in terms of solution composition?

$M = \frac{\text{moles of solute}}{\text{liters of solution}}$

Q: A solution is labeled as $2.1\ M$ lithium fluoride ($\text{LiF}$). Which of the following best describes this solution?

There are $2.1$ moles of $\text{LiF}$ per liter of solution.

Question 1

Which of the following best defines molarity ($M$) in terms of solution composition?

Accepted Answer

$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$

Question 2

A chemist dissolves $2.5$ moles of sodium chloride ($	ext{NaCl}$) in enough water to make $0.500$ liters of solution. What is the molarity of the solution?

Accepted Answer

$5.0\ M$

Question 3

If $3.0$ moles of silver chloride ($	ext{AgCl}$) are dissolved to make $2.0$ liters of solution, what is the molarity?

Accepted Answer

$1.5\ M$

Question 4

A student dissolves $0.60$ moles of potassium nitrate ($	ext{KNO}_3$) in $0.800$ liters of solution. What is the molarity?

Accepted Answer

$0.75\ M$

Question 5

Which of the following statements about preparing a $1.0\ M$ solution is correct?

Accepted Answer

Dissolve $1.0$ mole of solute and add enough solvent to make $1.0$ liter of solution.

Question 6

If $4.2$ moles of lithium fluoride ($	ext{LiF}$) are dissolved in $2.0$ liters of solution, what is the molarity?

Accepted Answer

$2.1\ M$

Question 7

A solution is made by dissolving $18$ grams of hydrochloric acid ($	ext{HCl}$, molar mass $36.5\ 	ext{g/mol}$) in enough water to make $0.500$ liters of solution. What is the molarity?

Accepted Answer

$0.99\ M$

Question 8

Which of the following best explains why adding $1.0$ mole of sodium chloride to $1.0$ liter of water does not result in a $1.0\ M$ solution?

Accepted Answer

The final volume of the solution will be slightly more than $1.0$ liter after dissolving the solute.

Question 9

A chemist dissolves $33$ grams of beryllium hydride ($	ext{BeH}_2$, molar mass $9.0\ 	ext{g/mol}$) in enough water to make $0.60$ liters of solution. What is the molarity?

Accepted Answer

$6.1\ M$

Question 10

A solution is prepared by dissolving $734$ grams of lithium sulfate ($	ext{Li}_2	ext{SO}_4$, molar mass $110\ 	ext{g/mol}$) in enough water to make $2500$ mL of solution. What is the molarity?

Accepted Answer

$2.67\ M$

Question 11

How many moles of $	ext{ClO}_2$ are present in $9.0 	imes 10^{20}$ molecules?

Accepted Answer

$1.5 	imes 10^{-3}$ moles

Question 12

You have $9.0 	imes 10^{20}$ molecules of $	ext{ClO}_2$ dissolved to make $500$ mL of solution. What is the molarity?

Accepted Answer

$3.0 	imes 10^{-3}\ M$

Question 13

A student prepares two solutions: In the first, $1.0$ mole of sodium chloride is dissolved to make $1.0$ liter of solution. In the second, $1.0$ mole of sodium chloride is added to $1.0$ liters of water. Which statement is correct?

Accepted Answer

The first solution has a slightly higher molarity than the second.

Question 14

Which of the following is a correct step in calculating the molarity of a solution when given grams of solute and total solution volume?

Accepted Answer

Convert grams of solute to moles using the molar mass.

Question 15

A hospital pharmacist needs to prepare $0.75\ M$ potassium nitrate ($	ext{KNO}_3$) solution. If she has $0.60$ moles of $	ext{KNO}_3$, what volume of solution should she prepare?

Accepted Answer

$0.80$ liters

Question 16

A solution is labeled as $2.1\ M$ lithium fluoride ($	ext{LiF}$). Which of the following best describes this solution?

Accepted Answer

There are $2.1$ moles of $	ext{LiF}$ per liter of solution.

Molarity and Solution Concentration: Practice and Concepts

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