Anjela 17
Badges: 1
Rep:
?
#1
Report Thread starter 1 month ago
#1
When K2MnO4 is dissolved in water, the following reaction occurs.
a MnO4
2–(aq) + bH2O(l) → c MnO4

(aq) + d MnO2(s) + eOH–
(aq)
What are the values of a and c in the balanced chemical equation?
a c
A 2 1
B 3 2
C 4 3
D 5 4
Last edited by Anjela 17; 1 month ago
0
reply
deskochan
Badges: 11
Rep:
?
#2
Report 1 month ago
#2
This is a disproportionation reaction, that is MnO42- undergo oxidation and reduction
Oxidation: MnO42- ---> MnO4- (oxidation number of Mn change +6 to +7) ---(1)
Reduction: MnO42- --> MnO2 (oxidation number of Mn change +6 to +4) ---(2)
For (1), both numbers of Mn and oxygen atoms are equal, and just balance the charge is ok.
For (2), it needs to balance the charge and atoms by means of H2O and OH-.
MnO42- + 2H2O +2e- ---> MnO2 + 4OH-
MnO42- --> MnO4- + e-

COmbine together to get the answer
Last edited by deskochan; 1 month ago
0
reply
scimus63
Badges: 9
Rep:
?
#3
Report 1 month ago
#3
A is the answer
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Are you tempted to change your firm university choice on A-level results day?

Yes, I'll try and go to a uni higher up the league tables (14)
25%
Yes, there is a uni that I prefer and I'll fit in better (4)
7.14%
No I am happy with my choice (35)
62.5%
I'm using Clearing when I have my exam results (3)
5.36%

Watched Threads

View All