Question
Write with a balanced chemical equation what happens when: (i) concentrated nitric acid is heated with copper turnings. (ii) aluminium powder is boiled with a concentrated aqueous solution of sodium hydroxide.
Answer
(i) When concentrated nitric acid is heated with copper turnings, nitrogen dioxide (NO2) gas is evolved along with the formation of copper nitrate (Cu(NO3)2) and water (H2O). The balanced chemical equation for the reaction is:
8HNO3 + 3Cu → 3Cu(NO3)2 + 4H2O + 2NO2
(ii) When aluminium powder is boiled with a concentrated aqueous solution of sodium hydroxide, hydrogen gas (H2) evolves along with the formation of sodium aluminate (NaAlO2) and water (H2O). The balanced chemical equation for the reaction is:
2Al + 2NaOH + 6H2O → 2NaAl(O2H)4 + 3H2
The reaction produces a lot of heat and hydrogen gas is evolved with effervescence.
