CHEM 120 Exam 2 Questions & Answers 2026 | Complete
Study Guide | Graded A+
1. In the reaction H3O+ + PH3 ⇌ PH4+ + H2O, what is the role of H3O+ when the
reaction proceeds in the forward direction?
Base
Salt
Solvent
Acid
2. Describe the significance of the formula C1V1 = C2V2 in preparing solutions.
The formula determines the pressure of a gas in a container.
The formula C1V1 = C2V2 relates the concentrations and volumes of
the concentrated and diluted solutions, ensuring the amount of
solute remains constant.
The formula calculates the temperature of a solution.
The formula is used to find the density of a substance.
3. Describe the significance of osmolarity in biological systems.
Osmolarity is irrelevant to biological systems and only applies to
chemical reactions.
Osmolarity is crucial in biological systems as it affects the
movement of water across cell membranes, influencing cell
hydration and function.
Osmolarity measures the temperature of a solution, impacting
reaction rates.
, Osmolarity determines the pH level of a solution, which is vital for
enzyme activity.
4. Describe the role of the conjugate acid in a buffer solution containing CN-
ions.
The conjugate acid, HCN, increases the concentration of CN- ions.
The conjugate acid, HCN, reacts with water to form hydroxide ions.
The conjugate acid, HCN, helps maintain the pH by neutralizing
added bases.
The conjugate acid, HCN, decreases the overall concentration of the
solution.
5. For a perfectly dissociating 0.15 M NaCl solution, what is the osmolarity?
300 m Osmolar
0.15 ÷ 1.85 Osmolar
0.15 x 1.5 Osmolar
330 mOsmolar
6. When a perfect gas is cooled at constant pressure, its volume
stays the same
decreases
increases
7. Balance the reaction V + O2 → VO. When balanced, what is the coefficient in
front of the V?
2
1
, 3
4
8. What is the formula commonly used to prepare a dilute solution from a
concentrated solution?
M1V1 = M2V2
C = n/V
C1V1 = C2V2
PV = nRT
9. Describe how Boyle's Law applies to the scenario of compressing a gas from
80 L to 70 L.
Boyle's Law states that pressure and volume are directly related, so as
volume decreases, pressure decreases.
Boyle's Law states that temperature and volume are inversely related,
affecting pressure.
Boyle's Law states that the amount of gas affects its pressure and
volume directly.
Boyle's Law states that pressure and volume are inversely related
when temperature is constant, so as volume decreases, pressure
increases.
10. In the balanced chemical equation 2 NH3 + 3 CuO → 3 Cu + N2 + H2O, what
is the role of CuO?
Product
Solvent
Catalyst
Study Guide | Graded A+
1. In the reaction H3O+ + PH3 ⇌ PH4+ + H2O, what is the role of H3O+ when the
reaction proceeds in the forward direction?
Base
Salt
Solvent
Acid
2. Describe the significance of the formula C1V1 = C2V2 in preparing solutions.
The formula determines the pressure of a gas in a container.
The formula C1V1 = C2V2 relates the concentrations and volumes of
the concentrated and diluted solutions, ensuring the amount of
solute remains constant.
The formula calculates the temperature of a solution.
The formula is used to find the density of a substance.
3. Describe the significance of osmolarity in biological systems.
Osmolarity is irrelevant to biological systems and only applies to
chemical reactions.
Osmolarity is crucial in biological systems as it affects the
movement of water across cell membranes, influencing cell
hydration and function.
Osmolarity measures the temperature of a solution, impacting
reaction rates.
, Osmolarity determines the pH level of a solution, which is vital for
enzyme activity.
4. Describe the role of the conjugate acid in a buffer solution containing CN-
ions.
The conjugate acid, HCN, increases the concentration of CN- ions.
The conjugate acid, HCN, reacts with water to form hydroxide ions.
The conjugate acid, HCN, helps maintain the pH by neutralizing
added bases.
The conjugate acid, HCN, decreases the overall concentration of the
solution.
5. For a perfectly dissociating 0.15 M NaCl solution, what is the osmolarity?
300 m Osmolar
0.15 ÷ 1.85 Osmolar
0.15 x 1.5 Osmolar
330 mOsmolar
6. When a perfect gas is cooled at constant pressure, its volume
stays the same
decreases
increases
7. Balance the reaction V + O2 → VO. When balanced, what is the coefficient in
front of the V?
2
1
, 3
4
8. What is the formula commonly used to prepare a dilute solution from a
concentrated solution?
M1V1 = M2V2
C = n/V
C1V1 = C2V2
PV = nRT
9. Describe how Boyle's Law applies to the scenario of compressing a gas from
80 L to 70 L.
Boyle's Law states that pressure and volume are directly related, so as
volume decreases, pressure decreases.
Boyle's Law states that temperature and volume are inversely related,
affecting pressure.
Boyle's Law states that the amount of gas affects its pressure and
volume directly.
Boyle's Law states that pressure and volume are inversely related
when temperature is constant, so as volume decreases, pressure
increases.
10. In the balanced chemical equation 2 NH3 + 3 CuO → 3 Cu + N2 + H2O, what
is the role of CuO?
Product
Solvent
Catalyst
