Question

Find the number of moles of water that can be formed if you have 138 mol of hydrogen gas and 64 mol of oxygen gas.

Answer 1

Answer : The number of moles of water formed can be, 128 moles

Solution : Given,

Moles of hydrogen gas = 138 moles

Moles of oxygen gas = 64 moles

First we have to calculate the limiting and excess reagent.

The balanced chemical reaction will be,

$2H_2+O_2\rightarrow 2H_2O$

From the balanced reaction we conclude that,

As, 2 moles of hydrogen gas react with 1 mole of oxygen  gas

So, 138 moles of hydrogen gas react with $\frac{138}{2}=69$ moles of oxygen  gas

But the given moles of oxygen gas is 64 moles.

That means oxygen gas is a limiting reagent and hydrogen gas is an excess reagent.

Now we have to calculate the moles of water.

From the reaction we conclude that,

As, 2 moles of oxygen react to give 1 mole of water

So, 64 moles of oxygen react to give $64\times 2=128$ moles of water

Therefore, the number of moles of water formed can be, 128 moles

Answer 2

2H₂₍g₎ + O₂ ₍g₎→ 2H₂O

138 mol H₂ × (2 mol H₂O ÷ 2 mol H₂)= 138 mol H₂O
64 mol O₂ × (2 mol H₂O ÷ 1 mol O₂)= 128 mol H₂O

128 mol H₂O