Which of the following reactions is NOT an example of an oxidation-reduction reaction?

3Br2 + 2Ga----2GaBr3

H2S + Cl2----2HCl + S

2PbS + 3O2----2PbO +2SO2

K2Cr2O7 + KOH---- 2 K2CrO4 + H2O

Question

Which of the following reactions is NOT an example of an oxidation-reduction reaction?

3Br2 + 2Ga---->2GaBr3

H2S + Cl2---->2HCl + S

2PbS + 3O2---->2PbO +2SO2

K2Cr2O7 + KOH----> 2 K2CrO4 + H2O

aaronq · Answer

no exchange of electrons = not redox

anonymous · Answer

@aaronq can you take me through this problem

aaronq · Answer

sure, assign oxidation numbers to all the atoms, determine which didn't change.

anonymous · Answer

@aaronq can you show me please

anonymous · Answer

@aaronq is it B?

aaronq · Answer

okay, i'll do the first, 

$3\underbrace{Br_2}_0 + 2\underbrace{Ga}_{0}\rightarrow 2\underbrace{Ga}_{+3}\underbrace{Br_3}_{-1}$

so oxidation states changed, Br from 0 to -1 and Ga from 0 to +3, meaning it is a redox reaction.