1.21 The following data are obtained when dinitrogen and dioxygen react together to form different compounds:

  Mass of dinitrogen  Mass of dioxygen
(i) 14 g 16 g
(ii) 14 g 32 g
(iii) 28 g 32 g
(iv) 28 g 80 g

(a) Which law of chemical combination is obeyed by the above experimental data? Give its statement.

(b) Fill in the blanks in the following conversions:

(i) 1 km = ...................... mm = ...................... pm

(ii) 1 mg = ...................... kg = ...................... ng

(iii) 1 mL = ...................... L = ...................... dm3

(a) for the fixed mass of dinitrogen at 28 g, then the masses of dioxygen that will combine with the fixed mass of dinitrogen are 32 g, 64 g, 32 g, and 80 g.

The masses of dioxygen bear a whole number ratio of 1:2:2:5. Hence, the given experimental data obeys the law of multiple proportions. The law states that if two elements combine to form more than one compound, then the masses of one element that combines with the fixed mass of another element are in the ratio of small whole numbers. 

(b)
 (i) 1 km = 1 km ×  =1000 m1 km × 100 cm1 m × 10 mm1 cm
 1 km = 106 mm 
1 km = 1 km × 100 m1 km × 1 pm10-12 m
1 km = 1015 pm 
Hence, 1 km = 106 mm = 1015 pm

(ii) 1 mg = 1 mg  1 g1000 mg x 1 kg1000 g x
 1 mg = 10-6 kg 
1 mg = 1 mg × 
 
1 mg = 10-6 kg =
 
(iii) 1 mL = 1 mL × 1 L1000 mL
 1 mL = 10-3 L 
1 mL = 1 cm3  = 1 cm3 = 1 dm x 1 dm x 1 dm10 cm x 10 cm x 10 cm cm3
 1 mL = 103 dm3 
 1 mL = 10-3 L = 10-3 dm3