Which is cheaper for generating hydrogen gas by the action of excess acid on zinc or magnesium assuming the price of zinc as 10rupees per kg and magnesium 25rupees per kg
Answers
Magnesium is cheaper for the generation of hydrogen gas by the action of a dilute acid on it.
• Hydrogen can be generated by the action of either dilute HCl or dilute H₂SO₄ on zinc or magnesium metal.
i) Action of excess acid on zinc :
• Zn + 2dil. HCl → ZnCl₂ + H₂
• Zn + dil. H₂SO₄ → ZnSO₄ + H₂
• In both the cases, 1 mole of zinc produces one mole of hydrogen.
• We know that 1 mole of Zn = 65.38 g = 0.06538 kg
0.06538 kg of Zn gives one mole of hydrogen.
• Given, cost of zinc per kg = Rs 10
Total cost of zinc required to generate one mole of hydrogen = Rs. 10 × 0.06538
Or, Total cost of required zinc = Rs. 0.6538
ii) Action of excess acid on magnesium :
• Mg + 2dil. HCl → MgCl₂ + H₂
• Mg + dil. H₂SO₄ → MgSO₄ + H₂
In both the cases, 1 mole of magnesium produces one mole of hydrogen.
• We know that 1 mole of Mg = 12 g = 0.012 kg
0.012 kg of Mg gives one mole of hydrogen.
• Given, cost of magnesium per kg = Rs 25
Total cost of magnesium required to generate one mole of hydrogen = Rs. 25 × 0.012
Or, Total cost of required magnesium = Rs. 0.3
• Thus, the total cost of magnesium required to generate one mole of hydrogen is less than that of zinc. So, magnesium is cheaper than zinc.