Question

What are the products of electrolysis of one mole of pure distillied water?
a) 2g of H2 gas and 16g O2 produced
b) 8g H2 and 8g O2
c) 4g H2 and 32g O2
d) none of these

Answer 1

Reaction:

          (Electricity)

2 H2O --------------> 2H2 + O2

Concepts Involved:

• Mole Concept.

• Molar mass

• Electrolysis

• Free Ions

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=> Thus, 2 parts of water give 2 parts of Hydrogen gas and 1 part of Oxygen gas, during the electrolysis of distilled water.

=> Given that 1 mole of pure distilled water is electrolyzed.

=> So, 2 parts of water = 1 mole.

=> 1 part = 0.5 moles

=> So, 2*0.5 => 1 mole of Hydrogen gas and 1*0.5 => 0.5 mol of O2 is evolved.

Molar mass of H2 = 2*1 => 2 grams per mole.

Molar mass of O2 = 2*16 => 32 grams per mole.

=> So, 2*1 => 2 grams of Hydrogen gas and 32*0.5 => 16 grams of O2 is produced.

=>Thus, if electrolysis does take place, 16 grams of Oxygen and 2 grams of Hydrogen gas should be produced.

But, we also know that for electrolysis to take place, there should be free ions available, in pure distilled water, no free ions are present as water has not split to give Hydroxyl (OH-) and H+ ions yet.

So, the electrolysis cannot take place for pure distilled water due to absence of free ions, thus no gases will be evolved.

So, the correct option is (d) None of these.