Q: Which equation correctly represents the calculation of molarity?

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

Q: Which of the following is a correct conversion factor for a $5.0\ M$ $\mathrm{NaCl}$ solution?

$\frac{5.0\ \text{mol NaCl}}{1.0\ \text{L solution}}$

Question 1

Which of the following best defines molarity ($M$) in chemistry?

Accepted Answer

The number of moles of solute per liter of solution.

Question 2

A solution is prepared by dissolving $2.7\ \mathrm{g}$ of $\mathrm{NaOH}$ in enough water to make $2.50\ \mathrm{L}$ of solution. What is the molarity of the solution? $(\mathrm{Molar\ mass\ of\ NaOH} = 40.0\ \mathrm{g/mol})$

Accepted Answer

$0.027\ M$

Question 3

Which equation correctly represents the calculation of molarity?

Accepted Answer

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

Question 4

How many grams of $\mathrm{Na_3PO_4}$ $(\mathrm{Molar\ mass} = 163.8\ \mathrm{g/mol})$ are present in $300.0\ \mathrm{mL}$ of a $0.500\ M$ $\mathrm{Na_3PO_4}$ solution?

Accepted Answer

$24.6\ \mathrm{g}$

Question 5

A patient has a sodium level of $165\ \mathrm{mmol/L}$ in their blood. If $7.30\ \mathrm{mL}$ of blood is drawn, how many moles of sodium would be present?

Accepted Answer

$0.0012\ \mathrm{mol}$

Question 6

If $2.44\ \mathrm{g}$ of an unknown compound is dissolved in $100.0\ \mathrm{mL}$ of solution and the concentration is $0.673\ M$, what is the molar mass of the compound?

Accepted Answer

$36.2\ \mathrm{g/mol}$

Question 7

A solution with a final volume of $750.0\ \mathrm{mL}$ is prepared by dissolving $30.00\ \mathrm{g}$ of benzene $(C_6H_6,\ 	ext{density} = 0.877\ \mathrm{g/mL})$ in dichloromethane. What is the molarity of benzene in the solution? $(\mathrm{Molar\ mass\ of\ C_6H_6} = 78.11\ \mathrm{g/mol})$

Accepted Answer

$0.513\ M$

Question 8

Which of the following is a correct conversion factor for a $5.0\ M$ $\mathrm{NaCl}$ solution?

Accepted Answer

$\frac{5.0\ 	ext{mol NaCl}}{1.0\ 	ext{L solution}}$

Question 9

Which scenario best illustrates the use of molarity in a medical context?

Accepted Answer

Calculating the amount of sodium in a patient's blood sample to diagnose hypernatremia.

Question 10

A chemist needs to prepare $500.0\ \mathrm{mL}$ of a $1.00\ M$ $\mathrm{KCl}$ solution. How many grams of $\mathrm{KCl}$ $(\mathrm{Molar\ mass} = 74.55\ \mathrm{g/mol})$ are required?

Accepted Answer

$37.3\ \mathrm{g}$

Question 11

Which of the following statements about molarity is FALSE?

Accepted Answer

Molarity is independent of temperature.

Question 12

A laboratory technician needs to dilute a $6.0\ M$ $\mathrm{HCl}$ solution to make $1.0\ L$ of $1.0\ M$ $\mathrm{HCl}$. What volume of the $6.0\ M$ solution should be used?

Accepted Answer

$167\ \mathrm{mL}$

Molarity and Solution Calculations

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