Question

question 1
select the redox reactions.
□ zn₍ₛ₎ + 2agno₃₍ₐq₎ ==> zn(no₃)₂ + 2ag₍ₛ₎
□ h₂₍₉₎ + cl₂₍₉₎ ==> 2hcl₍₉₎
□ c₃h₈₍₉₎ + o₂₍₉₎ ==> co₂₍₉₎ + h₂o₍₉₎
□ 2kclo₃₍ₛ₎ ==> 2kcl₍ₗ₎ + 3o₂₍₉₎

Explanation:

Step1: Analyze first reaction

For $\ce{Zn_{(s)} + 2AgNO_{3(aq)} -> Zn(NO_{3})_{2} + 2Ag_{(s)}}$:
Zn oxidation state: 0 → +2 (oxidation, loses electrons).
Ag oxidation state: +1 → 0 (reduction, gains electrons).
So, redox reaction (both oxidation and reduction occur).

Step2: Analyze second reaction

For $\ce{H_{2(g)} + Cl_{2(g)} -> 2HCl_{(g)}}$:
H oxidation state: 0 → +1 (oxidation).
Cl oxidation state: 0 → -1 (reduction).
Redox reaction (electron transfer between H and Cl).

Step3: Analyze third reaction

For $\ce{C_{3}H_{8(g)} + O_{2(g)} -> CO_{2(g)} + H_{2}O_{(g)}}$ (combustion, a type of redox):
C oxidation state in $\ce{C3H8}$: -8/3 → +4 (oxidation).
O oxidation state: 0 → -2 (reduction).
Redox reaction (hydrocarbon combustion involves oxidation of C/H and reduction of O).

Step4: Analyze fourth reaction

For $\ce{2KClO_{3(s)} -> 2KCl_{(l)} + 3O_{2(g)}}$:
Cl oxidation state: +5 → -1 (reduction).
O oxidation state: -2 → 0 (oxidation).
Redox reaction (decomposition with electron transfer).

Answer:

All four reactions are redox reactions:

• $\boldsymbol{\ce{Zn_{(s)} + 2AgNO_{3(aq)} -> Zn(NO_{3})_{2} + 2Ag_{(s)}}}$ (redox: Zn oxidized, Ag reduced)
• $\boldsymbol{\ce{H_{2(g)} + Cl_{2(g)} -> 2HCl_{(g)}}}$ (redox: H oxidized, Cl reduced)
• $\boldsymbol{\ce{C_{3}H_{8(g)} + O_{2(g)} -> CO_{2(g)} + H_{2}O_{(g)}}}$ (redox: C/H oxidized, O reduced)
• $\boldsymbol{\ce{2KClO_{3(s)} -> 2KCl_{(l)} + 3O_{2(g)}}}$ (redox: Cl reduced, O oxidized)

(To select, check all four boxes as they all involve oxidation-reduction.)