Vraag 18

Een voorbeeld van een juiste berekening is:

$\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=10^{-7{,}00}=1{,}0 \cdot 10^{-7}(\mathrm{~mol} \mathrm{~L}^{-1}).

K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7\F_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7F_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}K_{\mathrm{z}}=\frac{\left[\mathrm{H}_3\mathrm{O}^{+}\right]\left[\mathrm{C}_7_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}$K_{\mathrm{z}}=\frac{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COO}^{-}\right]}{\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COOH}\right]}of\frac{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COOH}\right]}=\frac{K_{\mathrm{z}}}{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]}\frac{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}=\frac{K_{\mathrm{z}}}{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]}$\frac{\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COO}^{-}\right]}{\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COOH}\right]}=\frac{K_{\mathrm{z}}}{\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]}

De verhouding\frac{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COOH}\right]}=\frac{3{,}2 \cdot10^{-3}}{1{,}0 \cdot10^{-7}}=3{,}2\cdot10^4\frac{\left[\mathrm{C}_7\mathrm{F}_{15}\mathrm{COO}^{-}\right]}{\left[\mathrm{C}_7\mathrm{H}_{15}\mathrm{COOH}\right]}=\frac{3{,}2 \cdot10^{-3}}{1{,}0 \cdot10^{-7}}=3{,}2\cdot10^4$\frac{\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COO}^{-}\right]}{\left[\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{COOH}\right]}=\frac{3{,}2 \cdot 10^{-3}}{1{,}0 \cdot 10^{-7}}=3{,}2 \cdot 10^{4}.

Het percentage$\mathrm{C}_{7} \mathrm{~F}_{15} \mathrm{COOH}is$\frac{1}{3{,}2 \cdot 10^{4}+1} \times 10^{2}=3{,}1 \cdot 10^{-3}(\%).

Opmerking

De volgende omrekening niet aanrekenen:$\frac{1}{3{,}2 \cdot 10^{4}} \times 10^{2}=3{,}1 \cdot 10^{-3}(\%).