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,

$H ^{+}+ H _{2} O + NO _{3}^{-}+ H _{2} S \longrightarrow NH _{4}^{+}+ HSO _{4}^{-}$

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.