Question

The weight of NaOH required to prepare 0.2M, 200ml aqueous NaOH solution is

a) 1.6g
b) 0.8g
c) 0.4g
d) 2g

Answer 1

Answer:

Option A

Explanation:

Let us state the formual to be used for calcuating the number of moles in 200 ml solution

Moles of solute = Molarity × Liters of solution

0.2M/ 1L×0.200 L=0.04 mol

Now we know that the molar mass of NaoH is is 40.00 g/mol. Now we will using this to compute the mass of NaOH

For that we multiply the number of moles by 40.00 g/mol

Mass = 0.04 x 40

Mass of NaOH = 1.6 g

Hence option A is correct

Answer 2

Given:

Molarity, M = 0.2 M

Volume of solution, V = 200 ml

To Find:

The weight of NaOH required to prepare the required solution.

Calculation:

- M. wt of NaOH, w = 40 gm

- Let the mass of NaOH be w gm.

- Molarity = (w × 1000) / (M. wt × V)

⇒ 0.2 = (w × 1000) / (40 × 200)

⇒ w = 0.2 × (40 × 200) / 1000

⇒ w = 1.6 gm

- Hence, the correct answer is option (a) 1.6 gm.