Question

For each chemical reaction listed in the table below, decide whether the highlighted atom is being oxidized or reduced. 

reaction

Na₂ CO₃(s)+H₃ PO₄(aq) → Na₂ HPO₄(aq)+CO₂(g)+H₂ O(l) 

4 HF(g)+SiO₂(s) → SiF₄(g)+2 H₂ O(g) 

2 H₂(g)+O₂(g) → 2 H₂ O(g) 

4 KI(aq)+2 CuCl₂(aq) → 2 CuI(s)+I₂(aq)+4 KCl(aq)

Answer 1

1)

oxidation state of C in Na2CO3 is +4

oxidation state of C in CO2 is +4

So, this is neither oxidised nor reduced

2)

oxidation state of Si in SiO2 is +4

oxidation state of Si in SiF4 is +4

So, this is neither oxidised nor reduced

3)

oxidation state of O in O2 is 0

oxidation state of O in H2O is -2

So, this is reduced

4)

oxidation state of Cu in CuCl2 is +2

oxidation state of Cu in CuI is +1

So, this is reduced