Application of Gay-Lussac’s Law of Combining Volumes

Gay Lussac’s of combining volumes states that gases react in simple ratio with one another and to volumes of the products provided that temperature and pressure remain constant.

In this article, you will understand how to apply this law in calculation by studying the following examples below:

1.    2H₂ + O₂ → H₂O In the reaction above, what volume of hydrogen would be left over when 300cm³ of oxygen and hydrogen are exploded in a sealed tube?

 

1cm³ of oxygen = 2cm³ of hydrogen

300cm³ of oxygen = 2 x 300 = 600cm³

Volume of left over = 1000 – 600 = 400cm³

2.    Calculate the volume of carbon (II) oxide required to react with 40cm³ of oxygen. 2CO + O₂ → 2CO₂

1cm³of oxygen = 2cm³ of CO

40cm³ of oxygen = 2 x 40 = 80cm³

3.    Calculate the volume of residual gases that would be produced when 100cm³ of sulphur (IV) oxide reacts with 20cm³ of oxygen    2SO₂ + O₂ → 2SO₃

1cm³ of O₂ = 2cm³

20cm³ of O₂ = 2 x 20 = 40cm³

Volume of SO₂ left = 100 -40 = 60cm³

The volume of SO₃ produced

1cm³ of O₂ = 2cm³ of SO₃

20cm³ of O₂ = 2 x20 = 40cm³of SO₃

Total residual gases = 60 + 40 = 100cm³

4.    400cm³ of air containing 21% oxygen if 60cm³ of carbon (II) oxide burns completely with the air, calculate the volume of gases remaining.

 

Vol of oxygen in the air

21/100 x400 = 84cm³

But Vol. of oxygen that will react with CO

From the equation,

2cm³ of CO = 1cm³ of oxygen

60cm³ of CO = ½ x 60 = 30cm³

 

Vol. of remaining oxygen = 84-30 = 54cm³

Vol. of carbon (IV)oxide = 60cm³

Total residual gases = 60+54 = 114cm³

 This video below can be helpful