1. Which of the follwing buffered solutions has the greatest buffering capacity?
ID: 521300 • Letter: 1
Question
1. Which of the follwing buffered solutions has the greatest buffering capacity? A- 0.35 M HF and 0.25 M KF. B- 0.5 NaNO3 and 0.5 NH3 C- 100 mM HC204 and 100 mM Ca(C2O4)2. D - 10 M HCl and 1.0 M NaCl. I know the answer is A but I do not understand why.
2. Hydrogen gas (H2) has a molar entropy of 130.58 J/ (mole K) at 25 degrees Celcius. How many microstates does it have? The answer is 6.7 *10^6 and I used the formula S = klnW, but I did not get the correct answer.
3. Which of the following will not hae an effect on the solubility of potassium hydrogen sulfide? A. Addition of Sodium Phosphate B. Addition of an acid C. Addition of Base. Answer: A. Why would addition of acid or base effect solutbilty?
4. Which of the following reactions would have a decrease in entropy?
A. 2C(s) + O2(g) --> 2CO (g) ; B. N2O4 (g) --> 2NO2(g) C. N2O3 --> NO2(g) + NO(g). The answer is A. Can you explain why each of these leads to an increase/decrease in entropy as well as why A is the answer?
Explanation / Answer
1. Which of the follwing buffered solutions has the greatest buffering capacity?
A- 0.35 M HF and 0.25 M KF.
ratio = 0.25/0.35 = 0.714
B- 0.5 NaNO3 and 0.5 NH3
not a buffer
C- 100 mM HC204 and 100 mM Ca(C2O4)2.
ratio = 100/100 = 1
D - 10 M HCl and 1.0 M NaCl.
not a buffer!
clearly, th eonly option is either A or C
for C, it is mM, meaning miliMolar, they will not be able to eract with large amount of bases, such as 1 M of H+ or so, since they are very small in quantity
the best set is then A, with large amount of conjguate base, weak acid
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