Answer to Question #157367 in General Chemistry for Patrick

Question

When 50cm³ of hydrogen is sparked with 20cm³ of oxygen at 100°C and 1 atmospheric pressure, the total volume of the residual gas is?

Answer 1

Equation for the reaction:

2H₂O + O₂ ----> 2H₂O

mole ratio: 2 1 2

available vol. 50cm³ 20cm³ -

Reaction ratio : 40cm³ 20cm³ 40cm³

Residual gas : 10cm³ - 40cm³

Residual gas = unreacted hydrogen + formed water(g)

= 10 cm³ + 40 cm³

= 50cm³ 

Equation for the reaction:

2H₂O + O₂ ----> 2H₂O

to calculate volume of residual gas,

since 1 mole O₂ is 20cm³,

2 moles of H₂ will be 20 * 2 = 40cm³.

Meanwhile volume of H₂ given is 50cm³ and 40cm³ was used for the sparking(reaction).

Volume of unreacted gas is 50 - 40 = 10cm³.

volume of residual gas = volume of unreacted gas + volume of product gas

10cm³ + 40cm³ = 50cm³.