(i)What mass of hydrogen peroxide will be present in 2 L of a 5 molar solution ?
(ii) Calculate the mass of oxygen which will be liberated by the decomposition of 200 ml of this solution.

Explanation

(i)Mol mass of `H_2O_2=34 "g mol"^(-1)`
`therefore` 1L of 5 M solution of `H_2O_2` will contain 34 x 5 g `H_2O_2`
2L of 5 M solution of `H_2O_2` will contain 34 x 2 x 5=340 g `H_2O_2`
(ii) 0.2 L or 200 mL of 5 M solution will contain `H_2O_2`
`=(340xx0.2)/2`=34 g `H_2O_2`
Now, `{:(2H_2O_2 to , 2H_2O + O_2),(2 xx 34 = 68 gm , 2 xx 16 =32 gm):}`
Now, 68 g of `H_2O_2` on decomposition will give `O_2` =32 g
34 g of `H_2O_2` on decomposition will give
`=(32xx34)/68`=16 g `O_2`.