Chemistry 1220 Spring Semester 2023 Quiz I
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Chemistry 1220
Spring Semester 2023
Quiz I
1. (10 pts) Answer the following questions regarding the enthalpy and entropy changes when a solution forms.
a) What is the sign for the change in enthalpy for the separation of solute particles? Explain!
b) What is the sign for the change in enthalpy of mixing (solvation)? Explain!
c) If the ΔHsoln > 0 what does this mean about the overall relative strengths of attractive forces between solute and solvent particles when they mix compared to the attractive forces between the solute particles themselves and those between the solvent particles themselves? (i.e. Overall, are the attractive forces between unlike particles stronger or weaker than those between like particles?) Explain!
d) Is the solution process in part (c) ideal, endothermic or exothermic? (circle one)
e) Is an increase in disorder (entropy) necessary for this solution process? Explain!
f) Sketch an enthalpy change diagram (as done in lecture or the book) corresponding to ΔHsoln > 0. Label all ΔH’s (being more specific than something like ΔH1), including the ΔHsoln , on the diagram.
2. (3 pts) The heat of solution, ΔHsoln, for a substance in water is - 10.5 kJ/mol. The heat required to separate the solute particles is 155.0 kJ/mol. The heat required to separate the solvent particles is 210.0 kJ/mol. Estimate the heat of mixing, ΔHmix, (also called the heat of solvation, ΔHsolvation), for the solution process (kJ/mol)?
3. (2 pts) The solubility of a solid solute is 32.3 g solute/100 g H2O at 20 EC. What minimum mass (in grams) of solute would need to be added to 13.1 g H2O at 20 EC to make the solution saturated?
4. (4 pts) Which of the following are soluble in water, H2O, and WHY (give a brief explanationdealing w. IAF & type of compound; ionic, polar, nonpolar for both solute and solvent)?
(Circle all that apply.)
NH4ClO3 C6H12 CH3OH CCl4
5. (8 pts) When CH3OCH3 dissolves in H2O forces of attraction are being broken in the solute and in the
solvent and attractive forces are formed between the solute and solvent. Answer the following questions
concerning this process. (H, C, N and O are in groups 1A, 4A, 5A and 6A, respectively. H, C, N and O
have 1, 6, 7 and 8 electrons, respectively.) Explain your choices!
a) What forces of attraction are broken between CH3OCH3 molecules?
b) What forces of attraction are broken between H2O molecules?
c) What forces of attraction are formed between CH3OCH3 and H2O in forming the solution?
6. (2 pts) What happens to the solubility of a gas in water as temperature increases?
7. (3 pts) What volume (in L) of a 133 ppm NH3 solution with a density of 0.998 g/mL is required to
provide 0.0175 grams of NH3? (Form. wts. : NH3 = 17.03, H2O = 18.02)
8. (8 pts) A 16.0 M nitric acid, HNO3 , solution has a density of 1.42 g/mL.
(Form. wts. : HNO3 = 63.01, H2O = 18.02)
a) (4 pts) What is the molality of HNO3?
b) (4 pts) What is the mole fraction of HNO3?
9. (5 pts) A 7.69 m H2 SO4 solution has a density of 1.329 g/mL. What is the solubility of H2 SO4?
(Form. wts. : H2 SO4 = 98.08, H2O = 18.02)
2023-02-09