Question

Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?

Answer 1

Calculating the amount of Oxygen required:

Given, Hydrogen and Oxygen combine in the ratio $1:8$ by mass

So we can say that the amount of Oxygen required to react with 1g of Hydrogen to form water is 8g

Hence, the amount of Oxygen needed to react completely with 3g of Hydrogen is $3\times 8=24\mathrm{g}$

Therefore, 24g of Oxygen is required to react completely with 3g of hydrogen gas to form water.