1. if the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.00, which of the following is TRUE?
a. [HCHO2] > [NaCHO2]
b. [HCHO2] < [NaCHO2]
c. [HCHO2] << [NaCHO2]
d. it is not possible to make a buffer of this ph from HCHO2 and NaCHO2.
e. [HCHO2] = [NaCHO2]
2. Which of the following solutions is a good buffer system?
a. A soln that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2
b. a soln that is 0.10 M HF and 0.10 M LiC2H3O2
c. a soln that is 0.10 M HCl and 0.10 M HN4+
d. a soln that is 0.10 M NaOH and 0.10 M KOH
e. none of these is a buffer system
3. Identify a good buffer
a. significant amounts of both a weak acid and its conjugate base
b. small amounts of both a strong acid and a weak acid
c. significant amounts of both a strong base and a weak base
d. significant amounts of both a weak acid and a strong base
e. small amounts of both a weak acid and its conjugate base
Chemistry help?
2020-04-05 11:15 pm
回答 (2)
2020-04-06 12:34 am
✔ 最佳答案
1.Henderson-Hasselbalch equation:
pH = pKa + log([NaCHO₂]/[HCHO₂])
3.00 = 3.74 + log([NaCHO₂]/[HCHO₂])
log([NaCHO₂]/[HCHO₂]) = -0.74
[NaCHO₂]/[HCHO₂] = 10⁻⁰˙⁷⁴ = 0.182 < 1
Hence, [HCHO₂] > [NaCHO₂]
The answer: a. [HCHO₂] > [NaCHO₂]
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2.
Option a is a solution mixture of a weak acid HC₂H₃O₂ and its conjugate base C₂H₃O₂⁻. It is a good buffer system.
Option b is a solution mixture of a weak acid HC₂H₃O₂ of and a conjugate base of another acid. It is not a good buffer system.
In option c, it should be NH₄⁺ instead of HN₄⁺. Option c is a solution mixture of a strong acid HCl and a weak acid NH₄⁺. It is not a good buffer system.
Option d is a solution mixture of a strong base NaOH and a strong base KOH. It is not a good buffer.
The answer: a. a solution that is 0.1 M HC₂H₃O₂ and 0.1 M LiC₂H₃O₂.
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3.
A buffer is the solution mixture of significant amount of both a weak acid and its conjugate base, or that of both a weal base and its conjugate acid.
The answer: a. significant amounts of both a weak acid and its conjugate base
2020-04-06 12:46 am
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收錄日期: 2021-04-30 17:39:59
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