Question

question 4 (2 points)
which of the following is a redox reaction?
○mg (s) + 2 hcl (aq) → mgcl₂ (aq) + h₂ (g)
○ki (aq) + agno₃ (aq) → kno₃ (aq) + agi (s)
○hcl (aq) + naoh (aq) → h₂o (l) + nacl (aq)
○pb(no₃)₂ (aq) + 2 nacl (aq) → pbcl₂ (s) + 2 nano₃

Explanation:

A redox reaction involves a transfer of electrons, which can be identified by changes in oxidation states. In the reaction $\text{Mg (s)}+2\text{ HCl (aq)}
ightarrow\text{MgCl}_2\text{ (aq)}+\text{H}_2\text{ (g)}$, magnesium goes from an oxidation state of 0 to +2 and hydrogen goes from +1 to 0. The other reactions are double - displacement reactions where there is no change in oxidation states.

Answer:

$\text{Mg (s)}+2\text{ HCl (aq)}
ightarrow\text{MgCl}_2\text{ (aq)}+\text{H}_2\text{ (g)}$