30 6.2 Autoionisation of Water

Practice questions

1. Does hydrogen ion concentration $\mathrm{H}{\phantom{A}}^{+}$ remain constant in all aqueous solutions?
   1. 1. 1. No, hydrogen ion concentration varies with the amount of water present in an aqueous solution.
         2. Yes, hydrogen ion concentration remains constant in all aqueous solutions because of the amount of water.
         3. Yes, because $\mathrm{H}{\phantom{A}}^{+}\times \mathrm{OH}{\phantom{A}}^{-}=1.0\times 10{\phantom{A}}^{-14}$
         4. No, hydrogen ion concentration varies with the amount of acid or base present in an aqueous solution.
2. For a given aqueous solution, if $[{\mathrm{H}}^{+}]=1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-3}\mathrm{M}$, what is $[\mathrm{OH}{\phantom{A}}^{-}]$?
   1. 1. 1. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-11}$
         2. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-6}$
         3. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-17}$
         4. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-14}$
3. For a given aqueous solution, if $[{\mathrm{H}}^{+}]=7.92\times {\phantom{A}}_{10}{\phantom{A}}^{-5}\mathrm{M}$, what is $[\mathrm{OH}{\phantom{A}}^{-}]$?
   1. 1. 1. $0.89\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
         2. $1.26\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
         3. $1.26\times {\phantom{A}}_{10}{\phantom{A}}^{-9}\mathrm{M}$
         4. $1.26\times {\phantom{A}}_{10}{\phantom{A}}^{-19}\mathrm{M}$
4. For a given aqueous solution, if $[{\mathrm{OH}}^{\text{-}}]=1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-5}\mathrm{M}$, what is $\mathrm{H}{\phantom{A}}^{+}$?
   1. 1. 1. $5.0\times {\phantom{A}}_{10}{\phantom{A}}^{-9}\mathrm{M}$
         2. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-6}\mathrm{M}$
         3. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-9}\mathrm{M}$
         4. $2.5\times {\phantom{A}}_{10}{\phantom{A}}^{-9}\mathrm{M}$
         5. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-14}\mathrm{M}$
5. For a given aqueous solution, if $[{\mathrm{OH}}^{\text{-}}]=3.77\times {\phantom{A}}_{10}{\phantom{A}}^{-4}\mathrm{M}$, what is $\mathrm{H}{\phantom{A}}^{+}$?
   1. 1. 1. $2.65\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
         2. $0.65\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$
         3. $2.65\times {\phantom{A}}_{10}{\phantom{A}}^{-11}\mathrm{M}$
         4. $1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-11}\mathrm{M}$
6. What are $[\mathrm{H}{\phantom{A}}^{+}]$ and $[\mathrm{OH}{\phantom{A}}^{-}]$ in a $0.344\mathrm{M}$ solution of $\mathrm{HNO}{\phantom{A}}_3$?
   1. 1. 1. $[{\mathrm{H}}^{+}]=0.657\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=0.91\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
         2. $[{\mathrm{H}}^{+}]{\phantom{A}}_1\cdot 0\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=1.0\times {\phantom{A}}_{10}{\phantom{A}}^{-14}\mathrm{M}$
         3. $[{\mathrm{H}}^{+}]=5.0\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=2.5\times {\phantom{A}}_{10}{\phantom{A}}^{-14}\mathrm{M}$
         4. $[{\mathrm{H}}^{+}]=0.344\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=2.91\times {\phantom{A}}_{10}{\phantom{A}}^{-14}\mathrm{M}$
7. What are $[\mathrm{H}{\phantom{A}}^{+}]$ and $[\mathrm{OH}{\phantom{A}}^{-}]$ in a $0.00338\mathrm{M}$ solution of $\mathrm{KOH}$?
   1. 1. 1. $[{\mathrm{H}}^{+}]=2.96\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=0.00338\mathrm{M}$
         2. $[{\mathrm{H}}^{+}]=0.00338\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=1.56\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$
         3. $[{\mathrm{H}}^{+}]=0.96\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=1\times {\phantom{A}}_{10}{\phantom{A}}^{-8}\mathrm{M}$
         4. $[{\mathrm{H}}^{+}]=0.96\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=1\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
8. If $\mathrm{HNO}{\phantom{A}}_2$ is dissociated only to an extent of $\text{Math input error}$, what are $[\mathrm{H}{\phantom{A}}^{+}]$ and $[\mathrm{OH}{\phantom{A}}^{-}]$ in a $0.307\mathrm{M}$ solution of $\mathrm{HNO}{\phantom{A}}_2$?
   1. 1. 1. 1. $[{\mathrm{H}}^{+}]=0.00137\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=0.78\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
            2. $[{\mathrm{H}}^{+}]=0.137\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=0.32\times {\phantom{A}}_{10}{\phantom{A}}^{-10}\mathrm{M}$
            3. $[{\mathrm{H}}^{+}]=1.37\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=7.32\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$
            4. $[{\mathrm{H}}^{+}]=0.00137\mathrm{M}$ and $[{\mathrm{OH}}^{\text{-}}]=7.32\times {\phantom{A}}_{10}{\phantom{A}}^{-12}\mathrm{M}$

Answers

1. 1. d
   2. a
   3. b
   4. c
   5. c
   6. d
   7. a
   8. d