Question

Given the reaction: 2H₂ + O₂ → 2H₂O The total number of grams of O₂ needed to produce 54 grams of water is _________.

Answer 1

Answer : The mass of $O_2$ needed are, 48 grams.

Explanation :

First we have to calculate the moles of $H_2O$

$\text{Moles of }H_2O=\frac{\text{Given mass }H_2O}{\text{Molar mass }H_2O}=\frac{54g}{18g/mol}=3mol$

Now we have to calculate the moles of $O_2$

The given balanced chemical reaction is:

$2H_2+O_2\rightarrow 2H_2O$

From the reaction, we conclude that

As, 2 mole of $H_2O$ produces from 1 mole of $O_2$

So, 3 mole of $H_2O$ produces from $\frac{3}{2}=1.5$ mole of $O_2$

Now we have to calculate the mass of $O_2$

$\text{ Mass of }O_2=\text{ Moles of }O_2\times \text{ Molar mass of }O_2$

Molar mass of $O_2$ = 32 g/mole

$\text{ Mass of }O_2=(1.5moles)\times (32g/mole)=48g$

Therefore, the mass of $O_2$ needed are, 48 grams.