Question

A liquid compound X of molecular mass 18 u can be obtained from a number of natural sources. All the animals and plants need liquid X for their survival. When an electric current is passed through 200 grams of pure liquid X under suitable conditions, then 178 grams of gas Y and 22 grams of gas Z are produced. Gas Y is produced at the positive electrode whereas gas Z is obtained at the negative electrode. Moreover, gas Y supports combustion whereas gas Z burns itself causing explosions.

1. Name (i) liquid X (ii) gas Y, and (iii) gas Z.
2. What is the ratio of the mass of element Z to the mass of element Y in the liquid X ?
3. Which law of chemical combination is illustrated by this example ?
4. Name two sources of liquid X.
5. State an important use of Y in our life.

Answer 1

(i) Liquid X is water (H₂O).
     (ii) Gas Y is oxygen.
    (iii) Gas Z is hydrogen.

The ratio of element Z to element Y by mass = 22:178
Therefore, ratio of Z : Y by mass = 1:8

The law of constant proportions is illustrated by this example.

Liquid X has already been stated as water. Oceans and rivers are the important sources of water on earth.

Y, oxygen, is essential for our survival. We breathe in oxygen during respiration.