JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Some Basic Concepts of Chemistry

5 g of NaOH was dissolved in deionized water to prepare a 450 mL stock solution. What volume (in

mL

) of this solution would be required to prepare 500 mL of 0.1 M solution?

Given : Molar Mass of

Na

O

and H is 23, 16 and 1

g mol^{- 1}

respectively

Answer: 180

Solution

The amount of NaOH taken is

\frac{5}{40} = 0.125

mol, since its molar mass is

23 + 16 + 1 = 40 g mo l^{- 1}

. Dissolving this in

450 mL

makes the stock molarity

\frac{0.125 \times 1000}{450} = \frac{125}{450} M

. On dilution the moles of NaOH are conserved, so

M_{1} V_{1} = M_{2} V_{2}

with

M_{2} V_{2} = 0.1 \times 500 = 50 mmol

. Hence

V_{1} = \frac{50 \times 450}{125}

, and the volume of stock solution required is

180 mL

JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Integer answer