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 will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?



Given reaction can be written as 

  C  +   O 2 → CO 2

(3g)     (8g)       (11g)


By the law of constant proportion, we know that

Two elements always combine to form a compound in a fixed ratio by mass.


It is given that 3g Carbon reacts with 8g Oxygen to form 11g CO 2 .

To find : Mass of Carbon Dioxide formed when 3g Carbon reacts with 50g Oxygen


Now, by law of of constant proportion

3g Carbon needs 8g of Oxygen to form 11g Carbon Dioxide.


Thus, the 3g Carbon will use 8g Oxygen from the available 50g to form 11g of Carbon Dioxide.

Now there is no more Carbon left to react with the remaining 42g (50g-  8g) Oxygen , hence the reaction will stop and no more Carbon Dioxide will be formed .


The chemical reaction for the equation can be written as

  C  +   O 2     →  CO 2 + O 2

(3g)     (50g)     (11g)   (42g)

  1. Class 9
  2. Chapter 3 Class 9 - Atoms And Molecules (Term 2)

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo