Chem II
November 14, 2021
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1. The decomposition of S02C,12 is first order in S02Cl s and has a rate constant of I .42 x 10-4 s”! at a certain temperature,
a) Wthat (s the half-life for this reaction. b) If the initial concentration of S02Cb is 0.80M, how long would it take for the concentration to decrease to 0.62M and. c) if the initial concentration is 0.25M. what concentration remains after 15.0 min?
2. A reaction has a rate constant of 1 .22 x 104 s-l at 18 oc and 0.230 at 68 Ç’c. Determine the activation energy barrier for this reaction. 8.3 14 J/molÛC (10 pt)
3. Consider the following three-step mechanism for the reaction (10 pt) fast
+ CHC13(p) + CC13(g) slow
Cllg) + CC13(g)
a) What is rhe overall reaction and, b) What is the predicted rate law?
4. What is the pH ofa solution containing 1.0 gm ofNaOH (MW= 40 g/mol) dissolved in 100 ml of water. (6 pt)
5. Is an aqueous solution for the following salts neutral. basic or acidic? Give a reason why. (3 pt each)
a) CoCl, b) NaC6H5C02 (sodium benzoate)
6. For the fòllowing reaction, C6H1206(s) will the amount of oxvgen gas increase or decrease with the following changes in the reaction. The reaction is endothermic. (2 pt each)
a) the temperature of the reaction is increased
b).increasing the reaction volume
c) removing C02 gas
‘7. The initial concentration of HI is 0.068 M, for 12 it is 0.055 M, and for 1-12 the equilibrium concentration is
0.045 M, Determine the equilibrium constant for the reaction below. (10 pt)
+ 2 HI(gÌ
8. A 36.0 wt% concentrated HCI solution has a density of .18 g/ml. Wffiat volume ofthis concentrated HCI solution should be used to prepare 500 ml of a pH 2.3 solution. (10 pt) M i
9. A 0.50 mol sample of PC’s is placed in a 500 ml reaction vessel and heated to 250 oc which decomposes as follows
PCI¶c) + Chcg)
ff equilibrium constant, K. is 18.0, what are the equilibrium concentrations of each? (10 pt)
10. A 0.10 M solution of the weak acid, HA- has a percent ionization of 2.2%. What is the acid ionization constant for HA? (10 pt)
I I . A solution initially had 0.065 M of the weak base ethvlamine (B) added. Represent ethylamine as B and the protonated form as BH+ Wthat is the pH and the concentration of B and BHA in this solution?
1.86 X ( 10 pt)