City University of New York
Lehman College Department of Chemistry
Level 3 and 4 Questions:
Consider the reaction NH₄NO₃(s)⇌N₂O(g)+2H₂O(g), K=0.665 at 525K.
If a 2 L reaction vessel contains 0.65 moles of N₂O(g), 1.2 moles of H₂O(g), and 0.3 moles of NH₄NO₃(s), which of the following statements is correct?
a. The amount of NH₄NO₃(s) will increase, K will not change
b. The amount of NH₄NO₃(s) will increase, K will get smaller
c. The amount of NH₄NO₃(s) will not change, K will not change
d. The amount of N₂O(g) will increase, K will not change
e. The amount of N₂O(g) will increase, K will get larger
Cyclohexane (C₆H₁₂) undergoes a molecular rearrangement in the presence of AlCl₃ to form methylcyclopentane (CH₃C₅H₉) according to the equation:
C₆H₁₂⇌CH₃C₅H₉, Kc=0.143
If the initial concentrations of C₆H₁₂ and CH₃C₅H₉ are 0.200M and 0.075M, respectively, what are the equilibrium concentrations of these species?
a. [C₆H₁₂]=0.041M
[CH₃C₅H₉]=0.041M
b. [C₆H₁₂]=0.241M
c. [C₆H₁₂]=0.159M
d. [C₆H₁₂]=0.253M
Which of the following statements about a sample of pure water will ALWAYS be true?
a. [H₃O⁺]=1.0×10^(-7)M
b. pOH is always equal to 7.
c. Water always has a neutral pH.
d. [H₃O⁺] is always equal to the [OH⁻] in pure water.
e. Two of the above statements are true.
Which of the following compounds would produce a solution with a pH above 7 when dissolved in water?
a. MgCl₂
b. NaH₂PO₄
c. NH₄NO₃
d. KOCl
Two of the above compounds would produce a basic solution.
What ratio of NH₄Cl to NH₃ should be used to make a buffer with pH=8.50?
a. 5.7
b. 0.18
c. 0.75
d. 3.75
e. You cannot achieve this pH using an ammonium buffer.
