Answer:
1. Generally metals reacts with acids to form salt and releases hydrogen gas.
Metal + Acid → Salt + Hydrogen Gas
2. Magnesium reacts with acids to form salt and releases hydrogen gas which is tested by burning.
E.g. Mg (s) + 2HCl (l) → MgCl2 (s) + H2 (g)
Mg (s) + H2SO4 (l) → MgSO4 (s) + H2 (g)
2Al (s) + 6 HCl (l) → 2AlCl3 (s) + 6H2 (g)
Zn (s) + 2HCl (l) → ZnCl2 (s) + H2 (g)
Zn (s) + H2SO4 (l) → ZnSO4 (s) + H2 (g)
Fe (s) + 2HCl (l) → FeCl2 (s) + H2 (g)
Some metals reacts with dilute Nitric acid (HNO3) and produces salt and any of the nitrogen oxides (N2O, NO, NO2) and water. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2).
Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
However magnesium and manganese react with very dilute HNO3 to evolve H2 gas.
Mg + 2HNO3 → Mg(NO3)2 + H2
Such reaction is the most exothermic.
The reactivity of metals towards the acids decreases in the order Mg > Al > Zn > Fe. In the case of copper, no bubbles were seen and the temperature also remained unchanged. This shows that copper does not react with dilute HCl.
Step-by-step explanation: