You dispose of a $0.200\;M$ solution of $H_3C_6H_5O_7$
(citric acid, $K_a$ $=$ $3.5\cdot 10^{-4}$)
Equilibrium of hydrolysis:
$H_3C_6H_5O_7$ $+$ $H_2O$
$H_3O^+$ $+$ $H_2C_6H_5O_7^-$
What are the equilibrium concentrations of each species?
a) $0.200\;M$, $x\;M$, $(0.200-x)\;M$ b) $0\;M$, $0.200\;M$, $0.200\;M$ c) $(0.200-x)\;M$, $x\;M$, $(0.200+x)\;M$ d) $(0.200-x)\;M$, $x\;M$, $x\;M$
The answer d) is correct, $(0.200 - x)\;M$, $0$ $ +$ $ x$ $=$ $x\;M$, $0$ $ +$ $ x$ $=$ $x\;M$.