Question

What would be the total mass of the products of a reaction in which 10 grams of water decomposes into the elements hydrogen and oxygen?

Answer 1

Assuming the reaction went all the way to completion, the law of conversation of mass states that the mass of the products must be equivalent to the mass of the reactants. So the total mass of the products is 10 grams.

Answer 2

Answer : The total mass of products of the reaction is 10 grams.

Explanation :

The balanced chemical reaction will be,

$2H_2O\rightarrow 2H_2+O_2$

First we have to calculate the moles of water.

$\text{ Moles of }H_2O=\frac{\text{ Mass of }H_2O}{\text{ Molar mass of }H_2O}=\frac{10g}{18g/mole}=0.555moles$

Now we have to calculate the moles of hydrogen and oxygen.

From the balanced reaction we conclude that

As, 2 mole of $H_2O$ to give 2 mole of $H_2$

So, 0.555 mole of $H_2O$ to give 0.555 mole of $H_2$

and,

As, 2 mole of $H_2O$ to give 1 mole of $O_2$

So, 0.555 mole of $H_2O$ to give $frac{0.555}{2}=0.278$ mole of $O_2$

Now we have to calculate the mass of hydrogen and oxygen.

$\text{ Mass of }H_2=\text{ Moles of }H_2\times \text{ Molar mass of }H_2=(0.555moles)\times (2g/mole)=1.11g$

and,

$\text{ Mass of }O_2=\text{ Moles of }O_2\times \text{ Molar mass of }O_2=(0.278moles)\times (32g/mole)=8.89g$

Now we have to calculate the total mass of products.

Total mass of products = Mass of hydrogen + Mass of oxygen

Total mass of products = 1.11 g + 8.89 g

Total mass of products = 10 grams

Therefore, the total mass of products of the reaction is 10 grams.