34 atoms of Carbon (C) react with 22 molecules of Hydrogen gas (H2). How many molecules of methane (CH4) will be formed and what will be left over?

a. 17 molecules of methane formed, 5 molecules of hydrogen left over

b. 11 molecules of methane formed, 23 molecules of carbon left over

c. 5 molecules of methane formed, 29 atoms of carbon and 2 molecules of hydrogen left over

d. 22 molecules of methane formed, 12 atoms of carbon left over

Answer : The correct option is, (b) 11 molecules of methane formed, 23 molecules of carbon left over

Explanation :

First we have to calculate the limiting and excess reagent.

The balanced chemical reaction will be:

From the balanced chemical reaction we conclude that,

As, 1 atom of carbon react with 2 molecule of hydrogen gas.

So, 34 atoms of carbon react with molecules of hydrogen gas.

But only 22 molecules of hydrogen are available.  Now we see it in another way.

As, 2 molecules of hydrogen gas react with 1 atom of carbon.

So, 22 molecules of hydrogen atom gas react with atoms of carbon.

That means, hydrogen is a limiting reagent as it limits the formation of product and carbon is an excess reagent.

The excess atoms of carbon = (34-11) =23 atoms of carbon will be left over.

Now we have to calculate the number of molecules of methane.

As, 2 molecules of hydrogen gas react to give 1 molecule of methane.

So, 22 molecules of hydrogen atom gas react to give molecule of methane.

Hence, the correct option is, (b)