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?

Explanation

Here we have been given that hydrogen and oxygen always combine in the fixed ratio of `1 : 8` by mass. This means that :
`1 g` of hydrogen gas requires `= 8 g` of oxygen gas
So, `3 g` of hydrogen gas requires `= 8 xx 3 g` of oxygen gas
`= 24 g` of oxygen gas
Thus, `24` grams of oxygen would be required to react completely with 3 grams of hydrogen gas.