Irrespective of the source, pure sample of H2O always contains 88.89% by mass of oxygen and 11.11% by mass of hydrogen.

Question

1. Irrespective of the source, pure sample of H₂O always contains 88.89% by mass of oxygen and 11.11% by mass of hydrogen. 

(a) Which law is illustrated here? 

(b) State the law. 

2. Complete the table by filling in the blanks:

48 g O2	1.5 mol O2	….mL O2​​​​​​​​​​​​ (at STP)
… g Na	2 gram atom Na	2NA Na atoms
….g CO2	2.5 mol CO2	56 L (at STP)
8.5 g  NH3	……mol NH3	11.2 L (at STP)

Answer 1

1. (a) Law of definite proportions. 

(b) The same chemical compound always contains the same elements combined in the same fixed proportion by mass.

2. 

48 g O2	1.5 mol O2	33600 mL O2​​​​​​​​​​​​ (at STP)
46 g Na	2 gram atom Na	2Na Na atoms
110g CO2	2.5 mol CO2	56 L (at STP)
8.5 g  NH3	0.5 mol NH3	11.2 L (at STP)