Question

Which quantities are conserved in all oxidation- reduction reactions?

• A. Charge only
• B. Mass only
• C. Both charge and mass
• D. Neither charge nor mass

Answer 1

Answer: (C)

Oxidation involves loss of electrons and reduction involves gain of electrons, hence in case of oxidation-reduction reactions (redox reactions) charge remains conserved. Moreover, in all chemical reactions mass also remains conserved. eg, in the reaction,

$H^{+}+H_{2}O+N{O}_3^{-}+H_{2}S⟶N{H}_4^{+}+HS{O}_4^{-}$

Charge $+1+0+(-1)+0=+1+(-1)$

$=0$

Mass $1+18+(14+48)+(32+2)=(14+4)$

$+(1+32+64)$

$115=115$

$\therefore$ Both charge and mass remain conserved.