Question

Gas 420 mmHg CHALLENGE PROBLEMS: 1. When sodium metal is placed in water, it reacts to form sodium hydroxide and hydrogen gas. If 20.7 grams of sodium is placed in 25.2 mL of water, what volume of hydrogen gas will be produced, assuming the temperature is 25.0°C and the pressure is 670. mmHg (the approximate atmospheric pressure in El Paso).

Answer 1

Q1:

Moles of sodium = 20.7g/23g/mol = 0.9 mol

Moles of water = (25.2ml × 1g/ml)/18g/mol = 1.4 mol

Sodium is limiting reagent .

2 Na + 2 H₂O -----> 2 NaOH + H₂

Moles of H₂ produced = 1/2 × moles of Na = 0.9×1/2 = 0.45mol

PV = nRT

P = 670/760 atm = 0.88158atm

V = 0.45mol×0.0821atm-L/K.mol×298.15K/​​​​​0.88158atm = 12.4948 L

Volume of hydrogen gas produced = 12.5 L. (Answer)

Q2:

Volume of gas pipe = π ×(1.33)² × 20×100 / 1000 L. = 11.1143L

Pressure = 9928.45kPa = 9928.45/101.325 atm = 97.986atm

n = PV/RT = 97.986× 11.1143/(0.0821×296.15) = 44.79mol

Mass of butane that pipe can hold = 44.49mol × 58g/mol = 2597.9 g = 2.5979kg = 2.60kg. (Answer)

Q3: (a)

At constant n and V , P/T = constant

P/(273.15+ 39.5)K = 20684kPa/(273.15+24.444)K

P = 21730.5 kPa

(b)

The pressure reached is less than the maximum limit 24131kPa, hence the seal will not break at the given conditions .