Question

What mass of HNO₃ is present in 250.0 mL of a nitric acid solution having a pH = 5.10?

Short answer

For preparing 250.0 mL of a nitric acid solution having a pH =5.10 , mass of HNO₃required is 1.25 × 10^-4 g.

Step-by-step solution

Concentration of [H+] ion Calculation

[H⁺] ion concentration in solution with pH= 5.1 can be calculated as,

$$\begin{gathered} {\text{pH = - log[H}}^{\text{+}}\text{]} \\ {\text{[H}}^{\text{+}}\text{]=}{\text{10}}^{\text{- pH}}={10}^{-5.1}=7.94\times {10}^{-6}\text{mol/L} \end{gathered}$$

Step 2:Moles calculation from Molarity  

Molarity of solution is given as,

$\begin{array}{rcl}\text{M}& =& \frac{\text{Moles}}{\text{Volume(L)}}=7.94\times {10}^{-6}\text{mol/L}\\ \text{Moles}& =& 7.94\times {10}^{-6}\text{mol/L}\times 0.25\text{L}=1.985\times {10}^{-6}\text{mol}\\ & & \end{array}$

Mass calculation from Moles

Moles of the solution are calculated as

$$\begin{gathered} \text{Moles}=\frac{\text{Mass}}{\text{Molar}\text{mass}}=1.985\times {10}^{-6}\text{mol} \\ \text{Mass = Moles}\times \text{Molar mass} \\ \text{=}1.985\times {10}^{-6}\text{mol}\times \text{63} \\ \text{= 1.25}\times {10}^{-4}\text{g} \end{gathered}$$