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

$\mathrm{M} = \dfrac{\text{moles\ of\ solute}}{\text{volume\ of\ solution\ in\ liters}}$

Question 1

A laboratory technician needs to prepare 500.0 mL of a 0.250 M NaCl solution from a 2.00 M NaCl stock solution. What volume of the stock solution should be used?

Accepted Answer

$62.5\ \mathrm{mL}$

Question 2

Which of the following best describes an isolated system in thermodynamics?

Accepted Answer

A system that cannot exchange heat or mass with its surroundings.

Question 3

A 3.68 g sample of sucrose ($\mathrm{C_{12}H_{22}O_{11}}$) is dissolved in enough water to make 275.0 mL of solution. What is the molarity of the solution? (Molar mass of sucrose = $342\ \mathrm{g/mol}$)

Accepted Answer

$0.0382\ \mathrm{M}$

Question 4

Which of the following statements about dilution is correct?

Accepted Answer

The number of moles of solute remains constant, but the concentration decreases.

Question 5

A titration is performed to determine the concentration of a NaOH solution. If $45.7\ \mathrm{mL}$ of $0.500\ \mathrm{M}\ \mathrm{H_2SO_4}$ is required to neutralize $20.0\ \mathrm{mL}$ of NaOH, what is the concentration of the NaOH solution? (Balanced equation: $\mathrm{H_2SO_4} + 2\mathrm{NaOH} \rightarrow 2\mathrm{H_2O} + \mathrm{Na_2SO_4}$)

Accepted Answer

$1.14\ \mathrm{M}$

Question 6

Which of the following is the correct formula for molarity?

Accepted Answer

$\mathrm{M} = \dfrac{	ext{moles\ of\ solute}}{	ext{volume\ of\ solution\ in\ liters}}$

Question 7

A student mixes $25.0\ \mathrm{mL}$ of $1.00\ \mathrm{M}$ CuSO$_4$ solution with enough water to make $250.0\ \mathrm{mL}$ of solution. What is the final concentration of CuSO$_4$?

Accepted Answer

$0.10\ \mathrm{M}$

Question 8

Which of the following best describes the first law of thermodynamics?

Accepted Answer

Energy cannot be created or destroyed, only converted from one form to another.

Question 9

A chemist needs to prepare $100.0\ \mathrm{mL}$ of $0.200\ \mathrm{M}$ KNO$_3$ solution. What mass of KNO$_3$ (molar mass = $101\ \mathrm{g/mol}$) is required?

Accepted Answer

$0.505\ \mathrm{g}$

Question 10

Which of the following is NOT a correct description of a system in thermodynamics?

Accepted Answer

A closed system can exchange both heat and mass with its surroundings.

Question 11

During a chemical reaction, $150\ \mathrm{J}$ of heat is released and $50\ \mathrm{J}$ of work is done on the system. What is the change in internal energy ($\Delta E$) of the system?

Accepted Answer

$-100\ \mathrm{J}$

Question 12

A $0.250\ \mathrm{M}$ solution of HCl is prepared by diluting $50.0\ \mathrm{mL}$ of a stock solution. What was the concentration of the stock solution if the final volume is $200.0\ \mathrm{mL}$?

Accepted Answer

$1.00\ \mathrm{M}$

Question 13

Which of the following is a real-world example of energy conversion described by the first law of thermodynamics?

Accepted Answer

A car engine converting chemical energy from gasoline into kinetic energy and heat.

Question 14

In a titration, what is the equivalence point?

Accepted Answer

The point at which the amount of titrant added is stoichiometrically equivalent to the amount of analyte in the sample.

Question 15

A $10.0\ \mathrm{mL}$ sample of $0.200\ \mathrm{M}$ HCl is titrated with $0.100\ \mathrm{M}$ NaOH. What volume of NaOH is required to reach the equivalence point?

Accepted Answer

$20.0\ \mathrm{mL}$

Question 16

Which of the following best explains why energy is released when chemical bonds are formed?

Accepted Answer

Forming bonds results in a more stable, lower-energy arrangement of atoms.

Question 17

A solution is prepared by dissolving $5.00\ \mathrm{g}$ of KCl (molar mass = $74.6\ \mathrm{g/mol}$) in enough water to make $250.0\ \mathrm{mL}$ of solution. What is the molarity of the solution?

Accepted Answer

$0.268\ \mathrm{M}$

Solution Concentration, Preparation, and Dilution in General Chemistry

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