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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