Question

4grams of hydrogen are ignited with 4 grams of oxygen .the weight of water formed is?

Answer 1

the water formed will be 4.5 gram because of law of definte proportions . water combine in ratio of 1:8

Answer 2

Answer: 4.5 grams

Explanation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

$\text{Number of moles of hydrogen}=\frac{4g}{2g/mol}=2moles$

$\text{Number of moles of oxygen}=\frac{4g}{32g/mol}=0.125moles$

For the given balanced chemical equation:

$2H_2+O_2\rightarrow 2H_2O$

By Stoichiometry:

1 mole of oxygen reacts with 2 mole of  hydrogen

So, 0.125 moles of oxygen react with =$\frac{2}{1}\times 0.125=0.25mole$ of hydrogen

Oxygen is considered as a limiting reagent because it limits the formation of product.

1 mole of oxygen produce 2 moles of water.

0.125 moles of oxygen produce=$\frac{2}{1}\times 0.125=0.25moles$ of water.

Mass of water=$moles\times {\text {molar mass}}=0.25\times 18=4.5g$