Question

Which of the following reactions is/are redox reactions?  You may select more than one reaction.

		BaCl2(aq) + Na2SO4(aq) = BaSO4(s) + 2NaCl(aq)
		Cl2(g) + 2K(s) = 2KCl(s)
		O2− + H2O(l) = 2OH−
		PH3(g) + HNO3(g) = NO2(g) + 3H2O(l) + P(s)
		C6H12O6 + heat = 6C(s) + 6H2O(g)
		2HNO3(aq) + Ca(OH)2(aq) = 2H2O(l) + Ca(NO3)2(aq)

Answer 1

The reaction in which simultaneous process of oxidation and reduction is said to be redox reaction.

Lets discuss for each reaction

Reaction : 1

BaCl₂(aq) + Na₂SO₄(aq) = BaSO₄(s) + 2NaCl(aq)

In this reaction , No any metal reduced or oxidized. So this is not the redox reaction.

2)

Cl₂(g) + 2K(s) = 2KCl(s)

Here Cl2 is reduced from 0 oxidation state to -1 oxidation state so it is reduced.

And K goes from 0 oxidation state to +1 oxidation state so this Redox reaction

3)

O²⁻ + H₂O(l) = 2OH⁻

Here Oxygen goes from -1 to -2 so it is redueced.

H goes from +1 to +1 so no oxidation reaction

And this is not redox reaction.

4)

PH₃(g) + HNO₃(g) = NO₂(g) + 3H₂O(l) + P(s)

Here P goes from -3 to 0 so oxidized

N goes from +5 to +4 so reduced and this is Redox reaction.

5)

C₆H₁₂O₆ + heat = 6C(s) + 6H₂O(g)

There is no any change in O and H so no Redox reaction.

6)

2HNO₃(aq) + Ca(OH)₂(aq) = 2H₂O(l) + Ca(NO₃)₂(aq)

Here also no any change in any oxdiation state so no redox rection :

The answer:

Reaction 2 and 4 are REDOX reaction.