A sample of 0.125 g of an organic compound when analysed by Dumas' method yields 22.78 mL of nitrogen gas collected over KOH solution at 280 K and 759 mm Hg. The percentage of nitrogen in the given or

Question

A sample of 0.125 g of an organic compound when analysed by Dumas' method yields 22.78 mL of nitrogen gas collected over KOH solution at 280 K and 759 mm Hg. The percentage of nitrogen in the given organic compound is . (Nearest integer)

[Given: (a) vapour pressure of water at 280 K = 14.2 mm Hg; (b) R = 0.082 L atm K⁻¹ mol⁻¹]

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Step 1: Correct for Aqueous Tension

The  gas is collected over KOH solution. Note: KOH is used (not water), so KOH absorbs  but not . However, aqueous tension still applies since the KOH solution has a vapour pressure.

Given: Vapour pressure of water at 280 K = 14.2 mm Hg (this approximates the vapour pressure of the KOH solution)

Step 2: Convert Volume of N₂ to STP Using Ideal Gas Law

Given:
-  mL = 0.02278 L
-  K
-  mm Hg =  atm = 0.9800 atm
-  L·atm·K⁻¹·mol⁻¹

Step 3: Calculate Mass o

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