Total cell reaction in dry cell:

• a$\ce{Zn + 2NH4+ + 2MnO2 -> Zn^2+ + 2NH3 + Mn2O3 + H2O}$
• b$\ce{Zn + Cu^2+ -> Zn^2+ + Cu}$
• c$\ce{2NaCl -> 2Na + Cl2}$
• d$\ce{CaCO3 -> CaO + CO2}$