CBSE Class 11-science Answered

what is the value of concentration of [h3o] and [oh] in neutral aqueous solution a 298k?ste their ph and poh value

Asked by Prakash | 28 Jun, 2018, 18:09: PM

Expert Answer

Water undergoes self-ionisation to a small extent as,

2 straight H subscript 2 straight O space space rightwards harpoon over leftwards harpoon with blank on top space straight H subscript 3 straight O to the power of plus space space plus space space OH to the power of minus straight K subscript straight w space equals space left square bracket straight H subscript 3 straight O to the power of plus right square bracket space left square bracket OH to the power of minus right square bracket

The constant Kw is called as an ionic product of water.

Its value at 298K is 1.008 X 10^-14 Mol² L^-2.

I n space p u r e space w a t e r space left square bracket H subscript 3 O to the power of plus right square bracket space a n d space left square bracket O H to the power of minus right square bracket space a r e space e q u a l. space space space space space space space space space space space K subscript w space equals space space left square bracket H subscript 3 O to the power of plus right square bracket space space left square bracket O H to the power of minus right square bracket o r space space space space space space space space K subscript w space equals space space left square bracket H subscript 3 O to the power of plus right square bracket squared space space space space space space space space space space space space space space space space space because space space left square bracket H subscript 3 O to the power of plus right square bracket space equals space space left square bracket O H to the power of minus right square bracket space space space space space space space therefore space space left square bracket H subscript 3 O to the power of plus right square bracket space equals space square root of K subscript w end root A t space 298 K comma space left square bracket H subscript 3 O to the power of plus right square bracket space equals space square root of 1.008 space cross times 10 to the power of negative 14 end exponent end root space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 1 space cross times space 10 to the power of negative 7 end exponent space m o l space L to the power of negative 1 end exponent H e n c e comma space space left square bracket H subscript 3 O to the power of plus right square bracket space equals space space left square bracket O H to the power of minus right square bracket space equals space 1 space cross times space 10 to the power of negative 7 end exponent space m o l space L to the power of negative 1 end exponent

Now, let's find the pH and pOH value,

pH = log[H⁺]

= log [1 X 10^-7]

pH = 7

pH + pOH = 14

7 + pOH = 14

pOH = 7

Answered by Ramandeep | 29 Jun, 2018, 11:25: AM

CBSE Class 11-science Answered

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CBSE Class 11-science Answered

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