Chemistry, 27.12.2019 00:31, ehuntsman8221
Asolution is prepared by dissolving 0.56 g of benzoic acid (c6h5co2h, ka 6.4 ) in enough water to make 1.0 l of solution. calculate [c6h5co2h], , , , and the ph of this solution.
Answers: 2
![$\left[\mathrm{H}^{+}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right]=5.1 \times 10^{-4} \mathrm{M}$](/tpl/images/0434/1977/10f45.png)
![$\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right]=4.1 \times 10^{-3} \mathrm{M}$](/tpl/images/0434/1977/9a3e2.png)
![$\left[\mathrm{OH}^{-}\right]=1.9 \times 10^{-11} \mathrm{M}](/tpl/images/0434/1977/e5b4e.png)
and the number of moles (n) of benzoic acid:
![$\mathrm{K}_{a}=\frac{\left[\mathrm{H}^{+}\right]\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right]}{\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right]}=6.4 \times 10^{-5}$](/tpl/images/0434/1977/e74c4.png)
![$\left[\mathrm{H}^{+}\right]_{0}$](/tpl/images/0434/1977/f38bd.png)
is 0. (because of autonization)![$\left[\mathrm{H}^{+}\right]_{0}=10^{-7} \mathrm{M} \approx 0$](/tpl/images/0434/1977/a3a3d.png)
![$\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right]_{0}-\mathrm{x}=0.00459-\mathrm{x}$](/tpl/images/0434/1977/a086a.png)
![$\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right]_{0}+\mathrm{x}=0+\mathrm{x}=\mathrm{x}$](/tpl/images/0434/1977/89a6e.png)
![$\left[\mathrm{H}^{+}\right]=\left[\mathrm{H}^{+}\right]_{0}+x=0+x=x$](/tpl/images/0434/1977/2b64c.png)
![$\left[\mathrm{H}^{+}\right]$](/tpl/images/0434/1977/93e23.png)
is much smaller than 
to decide whether the following approximation is valid or not:
![$\mathrm{x}=4.9 \times 10^{-4}=\left[\mathrm{H}^{+}\right]$\\](/tpl/images/0434/1977/329c6.png)
of acid is dissociated.
:
![\mathrm{M}=\left[\mathrm{H}^{+}\right]=\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right]$](/tpl/images/0434/1977/6835a.png)
![$\left[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right]=0.00459-0.00051=4.1 \times 10^{-3} \mathrm{M}$](/tpl/images/0434/1977/3ea5f.png)
![$\left[\mathrm{OH}^{-}\right]=\frac{\mathrm{K}_{w}}{\left[\mathrm{H}^{+}\right]}=\frac{1.0 \times 10^{-14}}{5.1 \times 10^{-4}}=1.9 \times 10^{-11} \mathrm{M}$](/tpl/images/0434/1977/7340a.png)
![$\mathrm{pH}=-\log \left[\mathrm{H}^{+}\right]=-\log \left(5.1 \times 10^{-4}\right)=3.29$](/tpl/images/0434/1977/3ad18.png)
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Asolution is prepared by dissolving 0.56 g of benzoic acid (c6h5co2h, ka 6.4 ) in enough water to...
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