10. given the following acids and $k_a$ values:
$\text{hclo}_4$ $\text{hoac}$ $\text{hcn}$ $\text{hf}$
$1 \times 10^7$ $1.76 \times 10^{-5}$ $4.93 \times 10^{-10}$ $3.53 \times 10^{-4}$
which shows the conjugate bases listed by increasing strength?
a $\text{clo}_4^-$, $\text{f}^-$, $\text{oac}^-$, $\text{cn}^-$
b $\text{cn}^-$, $\text{f}^-$, $\text{oac}^-$, $\text{clo}_4^-$
c $\text{cn}^-$, $\text{oac}^-$, $\text{f}^-$, $\text{clo}_4^-$
d $\text{cn}^-$, $\text{clo}_4^-$, $\text{f}^-$, $\text{oac}^-$
e $\text{clo}_4^-$, $\text{oac}^-$, $\text{cn}^-$, $\text{f}^-$

15. given that the $k_a$ for $\text{hocl}$ is $3.5 \times 10^{-8}$, calculate the $k$ value for the reaction of $\text{hocl}$ with $\text{oh}^-$.
a $3.5 \times 10^{-22}$
b $3.5 \times 10^6$
c $2.9 \times 10^{-7}$
d $3.5 \times 10^{-8}$
e none of these

32. acetic acid ($\text{hc}_2\text{h}_3\text{o}_2$) is a weak acid ($k_a = 1.8 \times 10^{-5}$). calculate the ph of a $17.6\text{ m}$ $\text{hc}_2\text{h}_3\text{o}_2$ solution.
a $4.3$
b $6.4$
c $1.7$
d $0.97$
e $7.4$

52. what concentration of acetic acid ($k_a = 1.80 \times 10^{-5}$) has the same ph as that of $5.00 \times 10^{-3}\text{ m}$ $\text{hcl}$?
a $5.00 \times 10^{-3}\text{ m}$
b $3.60 \times 10^{-3}\text{ m}$
c $1.39\text{ m}$
d $5.00\text{ m}$
e none of these

consider the reaction $\text{hocl} + \text{f}^- \
ightleftharpoons \text{hf} + \text{ocl}^-$

Question

10. given the following acids and $k_a$ values:
$\text{hclo}_4$ $\text{hoac}$ $\text{hcn}$ $\text{hf}$
$1 \times 10^7$ $1.76 \times 10^{-5}$ $4.93 \times 10^{-10}$ $3.53 \times 10^{-4}$
which shows the conjugate bases listed by increasing strength?
a $\text{clo}_4^-$, $\text{f}^-$, $\text{oac}^-$, $\text{cn}^-$
b $\text{cn}^-$, $\text{f}^-$, $\text{oac}^-$, $\text{clo}_4^-$
c $\text{cn}^-$, $\text{oac}^-$, $\text{f}^-$, $\text{clo}_4^-$
d $\text{cn}^-$, $\text{clo}_4^-$, $\text{f}^-$, $\text{oac}^-$
e $\text{clo}_4^-$, $\text{oac}^-$, $\text{cn}^-$, $\text{f}^-$

15. given that the $k_a$ for $\text{hocl}$ is $3.5 \times 10^{-8}$, calculate the $k$ value for the reaction of $\text{hocl}$ with $\text{oh}^-$.
a $3.5 \times 10^{-22}$
b $3.5 \times 10^6$
c $2.9 \times 10^{-7}$
d $3.5 \times 10^{-8}$
e none of these

32. acetic acid ($\text{hc}_2\text{h}_3\text{o}_2$) is a weak acid ($k_a = 1.8 \times 10^{-5}$). calculate the ph of a $17.6\text{ m}$ $\text{hc}_2\text{h}_3\text{o}_2$ solution.
a $4.3$
b $6.4$
c $1.7$
d $0.97$
e $7.4$

52. what concentration of acetic acid ($k_a = 1.80 \times 10^{-5}$) has the same ph as that of $5.00 \times 10^{-3}\text{ m}$ $\text{hcl}$?
a $5.00 \times 10^{-3}\text{ m}$
b $3.60 \times 10^{-3}\text{ m}$
c $1.39\text{ m}$
d $5.00\text{ m}$
e none of these

consider the reaction $\text{hocl} + \text{f}^- \
ightleftharpoons \text{hf} + \text{ocl}^-$

Accepted Answer

{ "quality": "clear", "question_count": 4, "skills_matched": [ "step_cot", "explain_then_answer", "quick" ], "needs_drawing": false, "concepts_used": [], "new_concepts": [ "Acid Dissociation Constant", "Conjugate Base Strength", "Weak Acid pH" ], "current_concepts": [ "Acid Dissociation Constant", "Conjugate Base Strength", "Weak Acid pH", "Acid-Base Equilibrium" ] } ## Question 10: Rank conjugate base strength $$ \begin{aligned} &\text{Acid strength order (by decreasing } K_a\text{): } \text{HClO}_4 > \text{HF} > \text{HOAc} > \text{HCN} \ &K_a \text{ values: } 1 \times 10^7 > 3.53 \times 10^{-4} > 1.76 \times 10^{-5} > 4.93 \times 10^{-10} \ &\text{Conjugate base strength is inversely proportional to acid strength:} \ &\text{ClO}_4^- < \text{F}^- < \text{OAc}^- < \text{CN}^- \end{aligned} $$ ## Question 15: Calculate equilibrium constant for reaction with hydroxide $$ \begin{aligned} &\text{Reaction: } \text{HOCl} + \text{OH}^- ightleftharpoons \text{OCl}^- + \text{H}_2\text{O} \ &K = \frac{[\text{OCl}^-]}{[\text{HOCl}][\text{OH}^-]} = \frac{[\text{OCl}^-][\text{H}^+]}{[\text{HOCl}]} \times \frac{1}{[\text{H}^+][\text{OH}^-]} = \frac{K_a}{K_w} \ &K = \frac{3.5 \times 10^{-8}}{1.0 \times 10^{-14}} = 3.5 \times 10^6 \end{aligned} $$ ## Question 32: Calculate pH of weak acid solution $$ \begin{aligned} &[\text{H}^+] \approx \sqrt{K_a \cdot C} = \sqrt{(1.8 \times 10^{-5})(17.6)} \approx \sqrt{3.168 \times 10^{-4}} \approx 1.78 \times 10^{-2}\text{ M} \ &\text{pH} = -\log_{10}(1.78 \times 10^{-2}) \approx 1.75 \approx 1.7 \end{aligned} $$ ## Question 52: Find concentration of weak acid with same pH as strong acid $$ \begin{aligned} &[\text{H}^+] = [\text{HCl}] = 5.00 \times 10^{-3}\text{ M} \ &K_a = \frac{[\text{H}^+]^2}{C - [\text{H}^+]} \implies 1.80 \times 10^{-5} = \frac{(5.00 \times 10^{-3})^2}{C - 5.00 \times 10^{-3}} \ &C - 5.00 \times 10^{-3} = \frac{2.50 \times 10^{-5}}{1.80 \times 10^{-5}} = 1.389\text{ M} \implies C \approx 1.39\text{ M} \end{aligned} $$ ## Question 10 [A] $\text{ClO}_4^-$, $\text{F}^-$, $\text{OAc}^-$, $\text{CN}^-$

[B] $\text{CN}^-$, $\text{F}^-$, $\text{OAc}^-$, $\text{ClO}_4^-$

[C] $\text{CN}^-$, $\text{OAc}^-$, $\text{F}^-$, $\text{ClO}_4^-$

[D] $\text{CN}^-$, $\text{ClO}_4^-$, $\text{F}^-$, $\text{OAc}^-$

[E] $\text{ClO}_4^-$, $\text{OAc}^-$, $\text{CN}^-$, $\text{F}^-$ ## Question 15 [A] $3.5 \times 10^{-22}$

[B] $3.5 \times 10^6$

[C] $2.9 \times 10^{-7}$

[D] $3.5 \times 10^{-8}$

[E] none of these ## Question 32 [A] 4.3

[B] 6.4

[C] 1.7

[D] 0.97

[E] 7.4 ## Question 52 [A] $5.00 \times 10^{-3}\text{ M}$

[B] $3.60 \times 10^{-3}\text{ M}$

[C] $1.39\text{ M}$

[D] $5.00\text{ M}$

[E] none of these

{ "subject": "Natural Science", "question_type": "Multiple Choice", "knowledge_point": [ "Natural Science", "Chemistry", "Acid-Base Equilibria" ] }

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Question 10: Rank conjugate base strength

Question 15: Calculate equilibrium constant for reaction with hydroxide

Question 32: Calculate pH of weak acid solution

Question 52: Find concentration of weak acid with same pH as strong acid

Answer:

Question 10

Question 15

Question 32

Question 52