Hydrogen practice · Mixed difficulty

Option B (0.042361111) is correct. The moles of H2 produced are the same in both reactions, so the ratio of volumes is 1:1. Calculating the moles of Zn and then the volume of H2 allows for the ratio calculation.

Option C is correct because ${\mathrm{H}_\mathrm{2}}{\mathrm{O}_\mathrm{2}}$ is always stored in black bottles because it undergoes auto oxidation on prolonged standing.

Option D ($\mathrm{D}_2 \mathrm{CO}_3, \mathrm{D}_2 \mathrm{SO}_4, \mathrm{D}_3 \mathrm{PO}_4, \mathrm{DNO}_3$) is correct because heavy water ($D_2O$) reacts with acidic oxides to form deuterated acids.

Option A is correct because passing $\mathrm{C}{\mathrm{O}_2}$ into ${\mathrm{Ba}{\mathrm{O}_2}}$ is a method for the laboratory preparation of hydrogen peroxide.

Option B is correct because saline hydrides, formed by alkali and alkaline earth metals, readily donate electrons and thus act as strong reducing agents.

Option B (0.03) is correct because the percentage strength of 10 volume $H_2O_2$ is approximately 3%.

Option B (200 ppm) is correct because the hardness is calculated by converting moles of magnesium sulfate to ppm of calcium carbonate equivalent.