## Friday 5 January 2018

### When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide willbe formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?

Answer : We know that in burning process carbon utilises oxygen to form Carbon Dioxide .
Carbon + Oxygen => Carbon Dioxide + Heat Energy

Here as given,  in burning, 3.0 g of carbon utilises 8.00 g of oxygen to form 11.00 g of carbon dioxide.When 3.00 g of carbon is burnt in 50.00 g of oxygen, it will use just 8.00 g of oxygen from  the total of 50 gm of Oxygen to produce 11 gm of Carbon Dioxide. 42 gm of Oxygen will be left behind without any change.
The above answer is governed by the following two laws of chemical combination:

1. Law of conservation of mass which states that mass can neither be created nor destroyed in a chemical reaction.
Here in terms of mass 3g of Carbon and 50 gm of Oxygen combines to give 11 gm of Carbon Dioxide and 42 gm of unused Oxygen keeping the total mass of combining

chemicals 53 gm (3+50 gm)  by weight constant before and after the reaction.

2. Law of constant proportions which states that In a chemical substance the elements are always present in definite proportions by mass.Here respective of the excess quantity of Oxygen available for burning of same weight of Carbon, the amount of carbon dioxide will remain same.