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.

 

Answers (1)

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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