Hydrogen and oxygen combine in a ratio of 1:8 by mass to form water. What mass of oxygen gas is required to react completely with 3g of hydrogen gas?
Hydrogen and oxygen combine in a ratio of 1:8 means that 1g of hydrogen gas requires 8g of oxygen gas to form water.
Therefore, 3g of hydrogen gas will require = 8 × 3 = 24 g of oxygen
Thus, 24g of the oxygen gas is required to react completely with 3 g of hydrogen gas to form water.