Step 1
The reaction must be written and balanced:
Ca(s) + H2SO4(aq) → CaSO4(aq) + H2(g)
Step 2
Oxidation states need to be analyzed:
For Ca)
On the left, its charge is 0 (Ca(s))
On the right, its charge is +2 (CaSO4 => Ca+ + SO42-)
The half-reaction for this is given by:
Ca => Ca2+ + 2e- (oxidation reaction)
Therefore, Ca is being oxidized
Answer: Ca
