JEE Main · 2021 · 31 Aug 2021 · Shift 2 · Some Basic Concepts of Chemistry

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Sodium oxide reacts with water to produce sodium hydroxide. 20.0 g of sodium oxide is dissolved in 500 mL of water. Neglecting the change in volume, the concentration of the resulting NaOH solution is ______

\times 1 0^{- 1} M

. (Nearest integer)
[Atomic mass :

Na = 23.0, O = 16.0, H = 1.0

]

Answer: 13

Solution

Sodium oxide reacts as

N a_{2} O + H_{2} O \to 2NaOH

. The molar mass of

N a_{2} O

62

g/mol, so

20.0

g is

\frac{20.0}{62} = 0.3226

mol, producing

2 \times 0.3226 = 0.6452

mol of

NaOH

. In

500

mL the molarity is

\frac{0.6452}{0.500} = 1.29 M = 12.9 \times 1 0^{- 1} M

, so the value is

13

JEE Main · 2021 · 31 Aug 2021 · Shift 2 · Integer answer

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