1. What mass of hydrgen peroxide will be present in 2 L of a 5 molar solution?

2.  Calculate the mass of oxygen which well be liberated by the decomposition of 200 mL of this solution.


(i) Molar mass of H2O2=34 g mol-1
1 L of 5 M solution of H2O2 will contain 34×5 g H2O2.
2 L of 5 M solution of H2O2 will contain 34×5×2=340 g H2O2
Mass of H2O2 present in 2 L of 5 molar solution=340g
(ii) 0.2 L (or 200 mL) of 5 M solution will contain
340×0.22=34 g H2O22H2O22×34=68g2H2O+O22×16=32 g
68 g H2O2 on decomposition will give 32 g O2
34 g H2O2 on decomposition will give 32×3468=16 g O2