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QUESTION IMAGE

which chemical equations show an oxidation-reduction reaction? □ o₂ + 2…

Question

which chemical equations show an oxidation-reduction reaction?
□ o₂ + 2h₂ → 2h₂o
□ mgso₄ + cacl₂ → mgcl₂ + caso₄
□ 2al + 6hi → 2ali₃ + 3h₂
□ fecl₂ + na₂co₃ → feco₃ + 2nacl
□ 2agno₃ + na₂s → ag₂s + 2nano₃

Explanation:

Response

To determine which reactions are oxidation - reduction (redox) reactions, we need to check for changes in oxidation states of elements. A redox reaction involves the transfer of electrons, which is indicated by a change in oxidation number of one or more elements.

Reaction 1: $\boldsymbol{O_{2}+2H_{2}

ightarrow 2H_{2}O}$

  • For $O_2$: The oxidation state of $O$ in $O_2$ (elemental form) is $0$. In $H_2O$, the oxidation state of $O$ is $ - 2$.
  • For $H_2$: The oxidation state of $H$ in $H_2$ (elemental form) is $0$. In $H_2O$, the oxidation state of $H$ is $ + 1$.
  • Since the oxidation states of $O$ and $H$ change, this is a redox reaction.
Reaction 2: $\boldsymbol{MgSO_{4}+CaCl_{2}

ightarrow MgCl_{2}+CaSO_{4}}$

  • Let's find the oxidation states of each element:
  • In $MgSO_4$: $Mg$ has an oxidation state of $ + 2$, $S$ has an oxidation state of $ + 6$, and $O$ has an oxidation state of $ - 2$.
  • In $CaCl_2$: $Ca$ has an oxidation state of $ + 2$ and $Cl$ has an oxidation state of $ - 1$.
  • In $MgCl_2$: $Mg$ has an oxidation state of $ + 2$ and $Cl$ has an oxidation state of $ - 1$.
  • In $CaSO_4$: $Ca$ has an oxidation state of $ + 2$, $S$ has an oxidation state of $ + 6$, and $O$ has an oxidation state of $ - 2$.
  • There is no change in the oxidation states of any element. This is a double - displacement (precipitation) reaction, not a redox reaction.
Reaction 3: $\boldsymbol{2Al + 6HI

ightarrow 2AlI_{3}+3H_{2}}$

  • For $Al$: The oxidation state of $Al$ in its elemental form is $0$. In $AlI_3$, the oxidation state of $Al$ is $ + 3$.
  • For $H$: In $HI$, the oxidation state of $H$ is $ + 1$. In $H_2$ (elemental form), the oxidation state of $H$ is $0$.
  • Since the oxidation states of $Al$ and $H$ change, this is a redox reaction.
Reaction 4: $\boldsymbol{FeCl_{2}+Na_{2}CO_{3}

ightarrow FeCO_{3}+2NaCl}$

  • Let's find the oxidation states:
  • In $FeCl_2$: $Fe$ has an oxidation state of $ + 2$ and $Cl$ has an oxidation state of $ - 1$.
  • In $Na_2CO_3$: $Na$ has an oxidation state of $ + 1$, $C$ has an oxidation state of $ + 4$, and $O$ has an oxidation state of $ - 2$.
  • In $FeCO_3$: $Fe$ has an oxidation state of $ + 2$, $C$ has an oxidation state of $ + 4$, and $O$ has an oxidation state of $ - 2$.
  • In $NaCl$: $Na$ has an oxidation state of $ + 1$ and $Cl$ has an oxidation state of $ - 1$.
  • There is no change in the oxidation states of any element. This is a double - displacement (precipitation) reaction, not a redox reaction.
Reaction 5: $\boldsymbol{2AgNO_{3}+Na_{2}S

ightarrow Ag_{2}S + 2NaNO_{3}}$

  • Let's find the oxidation states:
  • In $AgNO_3$: $Ag$ has an oxidation state of $ + 1$, $N$ has an oxidation state of $ + 5$, and $O$ has an oxidation state of $ - 2$.
  • In $Na_2S$: $Na$ has an oxidation state of $ + 1$ and $S$ has an oxidation state of $ - 2$.
  • In $Ag_2S$: $Ag$ has an oxidation state of $ + 1$ and $S$ has an oxidation state of $ - 2$.
  • In $NaNO_3$: $Na$ has an oxidation state of $ + 1$, $N$ has an oxidation state of $ + 5$, and $O$ has an oxidation state of $ - 2$.
  • There is no change in the oxidation states of any element. This is a double - displacement (precipitation) reaction, not a redox reaction.

Answer:

  • $O_{2}+2H_{2}

ightarrow 2H_{2}O$

  • $2Al + 6HI

ightarrow 2AlI_{3}+3H_{2}$