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Standard IX

Chemistry

Hydronium Ion

A water sampl...

Question

A water sample has a pH of 9.25. The concentration of hydroxyl ions in the water sample is

3.020 m g / L

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10^{- 4.75} m m o l e s / L

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10^{- 9.25} m o l e s / L

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0.302 m g / L

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Solution

The correct option is D $0.302 m g / L$
$p H = 9.25$

We know,

$p H + p O H = 14$

$p O H = 14 - 9.25 = 4.75$

$[O H^{-}] = 10^{- p O H}$

$= 10^{- 4.75} m o l / / l i t r e$

Molecular weight of
$O H^{-} = 17 g$

Concentration of hydroxyl ions
$= 17 \times 10^{- 4.75} g / L$
$= 17 \times 10^{- 4.75} \times 1000 m g / L$
$= 0.302 m g / L$

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A water sample has a pH of 9.25. The concentration of hydroxyl ions in the water sample is

The correct option is D 0.302mg/LpH=9.25 We know, pH+pOH=14 pOH=14−9.25=4.75 [OH−]=10−pOH =10−4.75mol//litre Molecular weight of OH−=17g Concentration of hydroxyl ions =17×10−4.75g/L =17×10−4.75×1000mg/L =0.302mg/L