# Which one of the following statements is not true? Option 1) The conjugate base of $H_{2}PO{_{4}}^{-}$ is $HPO{_{4}}^{2-}$   Option 2) $pH+pOH= 14\: for \: all \: aqueous\: solutions.$ Option 3) $The\: pH\: of\: 1\times 10^{-8}M\: H\! C\! L \: is \: 8$   Option 4) 96,500 coulombs of electricity when passed through a $CuSO_{4}$ solution deposits 1 gram equivalent of copper at the cathode.

As we learnt in

Value of p(H) -

Acidic solution has p(H)  < 7

Basic solution has  p(H)  > 7

Neutral solution has p(H) = 7

$:pH$ of an acid cannot exceed 7 Here we should also conside $\left [ H^{+} \right ]$ that comes from $H_{2}O$

$Now\left [ H^{+} \right ]= \left [ H^{+} \right ]_{from HCl}+\left [ H^{+} \right ]_{from\: H_{2}O}$

$= 10^{-8}+10^{-7}= 10^{-8}+10\times 10^{-8}= 11\times 10^{-8}$

$\therefore pH= -\log \left ( 11\times 10^{-8} \right )= 6.9587$

Option 1)

The conjugate base of $H_{2}PO{_{4}}^{-}$ is $HPO{_{4}}^{2-}$

This option is incorrect.

Option 2)

$pH+pOH= 14\: for \: all \: aqueous\: solutions.$

This option is incorrect.

Option 3)

$The\: pH\: of\: 1\times 10^{-8}M\: H\! C\! L \: is \: 8$

This option is correct.

Option 4)

96,500 coulombs of electricity when passed through a $CuSO_{4}$ solution deposits 1 gram equivalent of copper at the cathode.

This option is incorrect.

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