Of the following four reactions, how many are oxidation-reduction reactions? NaOH + HCl $\rightarrow$ NaCl + H₂O
Cu + 2AgNO₃ $\rightarrow$ 2Ag + Cu(NO₃) ₂
Mg(OH) ₂ $\rightarrow$ MgO + H₂O
N₂ + 3H₂ $\rightarrow$ 2NH₃

Question

Of the following four reactions, how many are oxidation-reduction reactions? NaOH + HCl

\rightarrow

NaCl + H₂O
Cu + 2AgNO₃

\rightarrow

2Ag + Cu(NO₃) ₂
Mg(OH) ₂

\rightarrow

MgO + H₂O
N₂ + 3H₂

\rightarrow

2NH₃

Quizplus · Accepted Answer

An oxidation-reduction reaction involves a transfer of electrons between two species. In reaction 1 (NaOH + HCl), there is no transfer of electrons, so it is not an oxidation-reduction reaction. 
In reaction 2 (Cu + 2AgNO3), there is a transfer of electrons as the Cu atoms lose electrons and become positively charged ions, while the Ag+ ions gain electrons and become neutral atoms. Therefore, this is an oxidation-reduction reaction. 
In reaction 3 (Mg(OH)2), there is no transfer of electrons, so it is not an oxidation-reduction reaction. 
In reaction 4 (N2 + 3H2), there is a transfer of electrons as the N2 molecule gains electrons and the H2 molecules lose electrons. Therefore, this is an oxidation-reduction reaction. 
Since reactions 2 and 4 involve a transfer of electrons and are therefore oxidation-reduction reactions, the answer is C (2).

Of the Following Four Reactions, How Many Are Oxidation-Reduction Reactions →\rightarrow→

Of the Following Four Reactions, How Many Are Oxidation-Reduction Reactions $\rightarrow$