Arrange them in decreasing order of the weight of oxygen
i) 4.0g of NaOH ii) 4.8g of SO2
iii) 4.0 g of CO2 iv)2.8 g of CaO
iii, ii, i & iv
i) 4.0g of NaOH contains:
Molecular weight of NaOH = 23 + 16 + 1 = 40 g
40 g of NaOH → 16 g of Oxygen
4g of NaOH → 1.6g of Oxygen
ii) 4.8g of SO2 contains:
Molecular weight of SO2 = 32 + 32 = 64 g
64 g of SO2 → 32 g of Oxygen
4.8g of SO2 → 4.8 × 3264
4.8g of SO2 → 2.4 g of Oxygen
iii) 4.0 g of CO2 contains:
Molecular weight of CO2 = 12+ 16 + 16 = 44
44 g of CO2 → 32 g of Oxygen
4 g of CO2 → 4 × 3244
4g of CO2 → 2.9 g of Oxygen
iv) 2.8 g of CaO contains:
Molecular weight of CaO = 40+16 = 56
56 g of CaO → 16 g of Oxygen
2.8 g of CaO → 2.8 × 1656
2.8 g of CaO → 0.8g of Oxygen
So, the decreasing order of the weight of oxygen is iii, ii, i & iv