REGIONAL CHAMPIONSHIP 2024
GOIL REGIONAL CHAMPIONSHIP — GRAND FINAL, BONO AHAFO ZONE
Sunyani Senior High School: 38 points (Winner)
St. James Seminary & Senior High School: 31 points
Kintampo Senior High School: 30 points
Our Lady of Mount Carmel Girls' Senior High School: 18 points
QUESTION
Identify the oxidizing or reducing agent in the given reaction and give a reason based on oxidation states.
1. $Cu + HNO_3 \rightarrow Cu(NO_3)_2 + NO_2 + H_2O$
ANSWER: The reducing agent is $Cu$, because its oxidation state changes from $0$ to $+2$.
2. $ClO_3^- + SO_3^{2-} \rightarrow Cl^- + SO_4^{2-}$
ANSWER: The oxidizing agent is $ClO_3^-$, because the oxidation state of chlorine changes from $+5$ to $-1$.
3. $H_2S + HNO_3 \rightarrow S + NO$
ANSWER: The oxidizing agent is $HNO_3$, because the oxidation state of nitrogen changes from $+5$ to $+2$.
4. $Cr_2O_7^{2-} + CH_3OH \rightarrow Cr^{3+} + CO_2$
ANSWER: The oxidizing agent is $Cr$ in $Cr_2O_7^{2-}$, because its oxidation state changes from $+6$ to $+3$.
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PRACTICE QUESTIONS
1. QUESTION: Identify the oxidizing or reducing agent in the reaction $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$ and give a reason based on oxidation states.
ANSWER: The reducing agent is $Zn$, because its oxidation state changes from $0$ to $+2$.
SOLUTION:
Zinc loses electrons (is oxidised), so it reduces the copper(II) ions to copper.
2. QUESTION: Identify the oxidizing or reducing agent in the reaction $MnO_4^- + Fe^{2+} \rightarrow Mn^{2+} + Fe^{3+}$ and give a reason based on oxidation states.
ANSWER: The oxidizing agent is $MnO_4^-$, because the oxidation state of manganese changes from $+7$ to $+2$.
SOLUTION:
In $MnO_4^-$: $x+4(-2) = -1$, so $x = +7$.
3. QUESTION: Identify the oxidizing or reducing agent in the reaction $H_2S + SO_2 \rightarrow S + H_2O$ and give a reason based on oxidation states.
ANSWER: The reducing agent is $H_2S$, because the oxidation state of sulfur changes from $-2$ to $0$.
SOLUTION:
$SO_2$ is the oxidizing agent: its sulfur falls from $+4$ to $0$.
4. QUESTION: Identify the oxidizing or reducing agent in the reaction $Cl_2 + KBr \rightarrow KCl + Br_2$ and give a reason based on oxidation states.
ANSWER: The oxidizing agent is $Cl_2$, because the oxidation state of chlorine changes from $0$ to $-1$.
SOLUTION:
Bromide ions are oxidised to bromine, so $KBr$ is the reducing agent.
5. QUESTION: Identify the oxidizing or reducing agent in the reaction $FeCl_3 + SnCl_2 \rightarrow FeCl_2 + SnCl_4$ and give a reason based on oxidation states.
ANSWER: The reducing agent is $SnCl_2$, because the oxidation state of tin changes from $+2$ to $+4$.
SOLUTION:
Iron is reduced from $+3$ to $+2$, so $FeCl_3$ is the oxidizing agent.
6. QUESTION: Identify the oxidizing or reducing agent in the reaction $Cu + H_2SO_4 \rightarrow CuSO_4 + SO_2 + H_2O$ and give a reason based on oxidation states.
ANSWER: The oxidizing agent is $H_2SO_4$, because the oxidation state of sulfur changes from $+6$ to $+4$.
SOLUTION:
In $SO_2$: $x+2(-2) = 0$, so $x = +4$.