The pH of 1.0x10^-8 M HCl at 298 K is nearest to

JEE Advanced levelSingle correct optionDifficulty 3 of 3ie093

The pH of $1.0 \times 1 0^{- 8} M$ $HCl$ at 298 K is nearest to

The ionisation of water cannot be neglected. Let

[H X^{+}] = 1 0^{- 8} + y

and

[OH X^{-}] = y

, so

y (1 0^{- 8} + y) = 1 0^{- 14}

, giving

y = 9.512 e - 08

[H X^{+}] = 1.051 e - 07 M

and

pH = 6.98

, still acidic, below 7.

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