In the redox equation Ca2+ + 2e- → Ca, what process is occurring?

Which of the following reactions results in the oxidation of sulfur?

Which of the following acts as a reductant in the reaction: H_2(g) + Cl_2(g) → 2HCl(g)?

In the following redox reaction: 2Cr(OH)3 + 3OCl− + 4OH− → 2CrO4^{2−} + 3Cl− + 5H2O, which substance acts as the reducing agent?

Which of the following reactions is a combination redox reaction?

Which type of battery utilizes the redox reaction Zn(s) + 2 MnO2(s) → ZnO(s) + Mn2O3(s)?

In the following redox reaction: Cr2O7^{2-} + 3 HNO2 + 5 H^+ → 2 Cr^{3+} + 3 NO3^- + 4 H2O, which substance acts as the reducing agent?

Which of the following describes what takes place when iron (Fe^0) is oxidized to Fe^{2+} ions?

What happens when concentrated HNO3 is mixed with gold (Au) at room temperature?