Question

Try 1: X 48.4 TV 2 X 0.0000485 1. A sample of nitrogen gas is produced in a reaction and collected under water in a graduated cyliner. The temperature is 26.3°C and the volume of gas is 45.1 ml. During this experiment the total pressure in the graduated cylinder is 743 mm Hg. How many grams of nitrogen were collected? (The vapor pressure of water at 26°C is 25.2 torr.)

Answer 1

Pressure of N₂ produced = total pressure - vapor pressure of water

P = (743 mmHg) - (25.2 mmHg)

P = 717.8 mmHg

P = (717.8) x (0.00131579) atm

P = 0.9445 atm

Volume, V = 45.1 mL = 0.0451 L

Temperature, T = 26.3 + 273.15 K = 299.45 K

Therefore, according to ideal gas equation, No.of moles of N₂ is given by:

PV = nRT

n = (PV) / (RT)

n = (0.9445 atm * 0.0451 L) / (0.0821 *299.45 K)

n = 0.001733 mole

We have, Molar mass of N₂= 28.01 g/mol

Therefore, Mass of N₂ collected

Mass = (0.001733 mole) x ( 28.01 g/mol)

Mass = 0.0485 g ---------- (ANSWER)