Question

the pH of a solution obtained by mixing 100 ml of 0.2 M CH3COOH with 100 ml of 0.2 M and NaOH will be
(pka for CH3COOH = 4.74)​

Answer 1

Answer:

$\displaystyle{\text{pH}=8.87}$

Explanation:

We have given :

Concentration and volume of both acetic acid and sodium hydroxide.

We know for weak acid and strong base , we find pH as :

$\displaystyle{\text{pH}=7+\dfrac{1}{2}(\text{pK}_a+\log \text{C})}$

In question value of pKa is given :

First we have to find value of C :

We have reaction here :

$\displaystyle{\text{CH}_3\text{COOH}+\text{NaOH}\rightleftharpoons\text{CH}_3\text{COONa}+\text{H _2 O}}\\\\\displaystyle{20\text{m mol} \ \ \ \ \ \ 20\text{m mol}}$

Now on product side total volume = 100 + 100 = > 200 mL

So, concentration of Sodium acetate ( C ) = 20 / 200 = > 0.1 M

Now putting value in formula for get pH :

$\displaystyle{\text{pH}=7+\dfrac{1}{2}(\text{pK}_a+\log \text{C})}\\\\\\\displaystyle{\text{pH}=7+\dfrac{1}{2}(4.74+\log0.1)}\\\\\\\displaystyle{\text{pH}=7+\dfrac{1}{2}(4.74+\log 1+\log10^{-1})}\\\\\\\displaystyle{\text{pH}=7+\dfrac{1}{2}(4.74-1)}\\\\\\\displaystyle{\text{pH}=7+\dfrac{1}{2}(3.74)}\\\\\\\displaystyle{\text{pH}=7+1.87}\\\\\\\displaystyle{\text{pH}=8.87}$

Answer 2

Answer:

Thus, the correct option is (B).  If the pH of the solution is less than 7 then the solution is acidic in nature.

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Explanation: