Question

Using the equation 2H2+O2=2H2O, when 47g of water are produced, how many grams of hydrogen must react?

Answer 1

See , from the equation we can see that for forming two mole of H2O 2Mole of H2 has to react.

Mass of 2 Mole H2O is 18*2gm or 36gm.

So for forming 36 gm H2O 2×2 I.e. 4 gm H2 has to take part in reaction.

Therefore, to form 1 gm H2O 4÷36 gm of H2 has to take part.

So, for forming 47gm H2O (4÷36)×47 gm H2 has to take part

I.e. 5.22 gm of H2 has to take part

So, ans is 5.22 gm of hydrogen.

Hope it helps!!!

Answer 2

Answer: Mass of hydrogen gas that must react will be 5.22 grams.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$   ....(1)

Given mass of water = 47 g

Molar mass of water = 18 g/mol

Putting values in above equation, we get:

$\text{Moles of }H_2O=\frac{47g}{18g/mol}=2.61mol$

For the given balanced chemical equation:

$2H_2+O_2\rightarrow 2H_2O$

By Stoichiometry of the reaction:

2 moles of water are formed from 2 moles of hydrogen gas.

So, 2.61 moles of water will be formed from $\frac{2}{2}\times 2.61=2.61mol$ of hydrogen gas.

Now, calculating the mass of hydrogen by using equation 1:

Moles of hydrogen gas = 2.61 moles

Molar mass of hydrogen gas = 2 g/mol

Putting values in equation 1, we get:

$2.61mol=\frac{\text{Mass of hydrogen gas}}{2g/mol}\\\\\text{Mass of hydrogen gas}=5.22g$

Hence, mass of hydrogen gas that must react will be 5.22 grams.