Question

Molarity of NaOH in 200ml of an aqueous solution of it is 1M , find the change in molarity if 2g of NaOH is added to it
1) 1.25M
2)0.25M
3)0.50M
4)0.75M
PLEASE GIVE ME SOLUTION FOR THIS QUESTION

Answer 1

The Change in molarity  is 0.25 M

Explanation:

Molarity of the solution= 1 M

Volume of solution = 200ml

                                = 0.2 L

1M = $\frac{n}{0.2L}$

Then, no of moles NaOH present = 0.2 mol

Molar mass of NaOH= 40 g.$mol^{-1}$

Weight of NaOH=  8 gm

NaOH added = 2gm

Now total mass of NaOH = 8gm +2gm

                                         = 10 gm

10 gm NaOH = 0.25 mol of NaOH

Now the molarity of the solution = $\frac{0.25}{0.2}$ M

                                                      = 1.25 M

Change in molarity = (1.25-1) M

                                 = 0.25 M

Correct answer is (2) 0.25 M