Question

When hydrogen gas was passed over $ 8.08g $ of heated metal oxide, it was completely reduced and $ 1.8g $ of water was formed:
(A) What is the weight of oxygen in the metal oxide?
(B) What is the equivalent mass of the metal?

Answer 1

Hint: At first we will write what is given in the question. Now we will find what is formed when the hydrogen is passed through hot metal. We will define equivalent mass. After that we will calculate the equivalent mass of the metal.

Complete step by step solution:
Step1. The amount of heated metal oxide is $ 8.08g $ .
The amount of water formed is $ 1.8g $ .
Step2. When hydrogen gas is passed through heated metal oxide, the water is formed and the chemical composition of water is $ {H_2}O $ . It contains 16g of oxygen and two grams of hydrogen. So the $ 1.8g $ gram of water will contain $ 1.6g $ of oxygen.
Step3. Now we find the equivalent mass of the metal.
The equivalent mass is the number of parts by mass of a substance that combines with or displaces $ 1.008 $ parts by mass of hydrogen or eight parts of oxygen is called equivalent mass.
Step4. Mass of metal in its oxide is $ 8.08 - 1.6 = 6.48g $
Now the oxygen is combined with metal. So the eight gram of oxygen will be combined with $ \dfrac{{6.48}}{{1.6}} \times 8 = 32.4g $
So the equivalent mass of the metal is $ 32.4g $.

Note:
When a metal reacts with oxygen, a metal oxide is formed. One of the most famous examples is rust. When the iron reacts with the oxygen it slowly turns into iron oxide. That is why we often see the brown colour thing on the iron when it is exposed to the atmosphere.