Ch. 16 & 17 equilibrium & acid / base /   test  [70 points]                    Honors Chemistry

Show your work in an organized manner, includes any relevant equation / formula, proper units in your work / answer, and the proper number of significant figures in your answer.

Academic Honesty:   The answers on this test are my own.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you do not sign or violate any of the preceding items, your semester grade is a F.

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1.  What is the pH of  ___.  [10 points]

a.  5.0 mM HCl (strong acid)

b.  5.0 mM KOH (strong base)

2.  A buffer contains benzoic acid and sodium benzoate (C₆ H₅ COONa).  Write the net ionic equation involving the reaction between the buffer and ___.  [10 points]

a.  HNO₃   (strong acid)

b.  NaOH  (strong base)

3.  Calculate the pH of 75 mL of 1.0 mM benzoic acid (C₆ H₅ COOH;  K_a = 6.5 * 10^-5 )   [10 points]

4.  What is the solubility of barium fluoride in water ?  [8 points]

5.   The combustion of ethane:  C₂ H_{6 (g)}  +  0_{2 (g)}  <-->  CO_{2 (g)}   +  H₂ O _(g)   generates heat.  Upon reaching equilibrium, the system was disturbed by  ___; what is the effect on the [O₂ ] ?  [CO₂ ] ?  Rationalize your answer.  [12 points]

a.  decrease in volume
b.  addition of water vapor
c.  addition of Ne
d.  cooling the system

6.  N_{2 (g)}   +  H_{2 (g)} <--> NH_{3 (g)}

5.0 moles of N₂ and 10.0 moles of H₂ were added to a 20.0 L containter at 500 K.  At equilibrium, there was 3.0 moles of N₂ ; what is K_c of this reaction ?  [10 points]

7.  H_{2 (g)}   +  I_{2 (g)} <--> 2HI _(g)   K_c = 10

The initial concentration of H₂ and I₂ are 5.0 and 7.0 mM, respectively.  What is the equilibrium concentration of HI ?  [10 points]