1. The Ka of benzoic acid 1x10^-5. Which of the following would you choose as a
ID: 856824 • Letter: 1
Question
1. The Ka of benzoic acid 1x10^-5. Which of the following would you choose as a pH= 4.0 buffer?
a. A 1.0 M solution of benzoic acid
b. A 1.0 L solution containing 1.0 mole of benzoic acid and 1.0 mole of sodium benzoate
c. A 1.0 L solution containing 1.0 mole of benzoic acid and 0.10 mole of sodium benzoate
d. A 1.0 L solution containing 0.10 mole of benzoic acid and 1.0 mole of sodium benzoate
2. Which of the following equations best describes what takes place just after the equation point is reached in the titration of the weak base CLO^- (aq) with hydrobromic acid? Explain your choice!
a. H+ (aq) + ClO- (aq) ---> HClO (aq)
b. HClO (aq) <----> H+ (aq) + ClO- (aq)
c. ClO- (aq) + H2O <-----> HClO (aq) + OH- (aq)
d. HClO (aq) + OH- (aq) <---> ClO-(aq) + H2O
e) ClO- (aq) + Br-(aq) <-----> ClOBr^2- (aq)
Explanation / Answer
correct answer is : c. A 1.0 L solution containing 1.0 mole of benzoic acid and 0.10 mole of sodium benzoate
pH = pKa + log([salt]/[acid])
4 = 5 + log(0.1/1)
4 = 5-1
4 = 4
so pH is equals to 4
2) a. H+ (aq) + ClO- (aq) ---> HClO (aq)
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