# Question #b80cc

Nov 24, 2015

$0.066 \text{mol/l}$

#### Explanation:

${H}_{3} P {O}_{4 \left(a q\right)} + 3 N a O {H}_{\left(a q\right)} \rightarrow N {a}_{3} P {O}_{4 \left(a q\right)} + 3 {H}_{2} {O}_{\left(l\right)}$

No. moles $N a O H = c \times v = 0.250 \times 0.0425 = 0.01$

From the equation we can see that the no. moles of phosphoric acid must be 1/3 of this:

$\therefore n {H}_{3} P {O}_{4} = \frac{0.01}{3} = 0.0033$

$c = \frac{n}{v}$

So the concentration of the ${H}_{3} P {O}_{4}$ is given by:

$c = \frac{0.0033}{0.05} = 0.066 \text{mol/l}$