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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