a)Green color appears.
Burning splint test tells us us that it is hydrogen gas.
b)[tex]Ni+ H_2SO_4 \longrightarrow NiSO_4 + H_2 \uparrow[/tex]
c)There would be an effervescence. Upon passing the gas through lime water it turns milky $\implies$ gas is Carbon Dioxide.
d)$\NiCO_3+ H_2SO_4 \longrightarrow NiSO_4 + CO_2 +H_2O$
