Question

: If a 250. mL sample of the above buffer solution initially has 0.0800 mol H2C6H5O7 - and 0.0600 mol HC6H5O7 2- , what would be the new concentration of HC6H5O7 2- after 25.0 mL of 0.125 M NaOH is added to the buffer?

Answer 1

Answer: New concentration of $HC_{6}H_{5}O^{2-}_{7}$ is 0.23 M.

Explanation:

The given data is as follows.

     Moles of $HC_{6}H_{5}O^{2-}_{7}$ = 0.06 mol

     Moles of $H_{2}C_{6}H_{5}O_{7}$ = 0.08 mol

Therefore, moles of $OH^{-}$ added are as follows.

    Moles of $OH^{-}$ = $0.125 \times \frac{25}{1000}$

                          = 0.003125 mol

Now, new moles of $HC_{6}H_{5}O^{2-}_{7}$ = 0.06 + 0.003125

                     = 0.063125

Therefore, new concentration of $HC_{6}H_{5}O^{2-}_{7}$ will be calculated as follows.

       Concentration = $\frac{0.063125}{0.275}$

                               = 0.23 M

Thus, we can conclude that new concentration of $HC_{6}H_{5}O^{2-}_{7}$ is 0.23 M.