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Use the ionic equations, for Sn2+ it's:
Can someone explain how is the answer B?
Sn2+ --> Sn4+ + 2e-
and for Mn2+ ions:
8H+ + MnO4^- + 5e- --> Mn2+ + 4H2O
but the problem is both equations are not balanced there are 2 electrons in the first one while 5 electrons in the 2nd one, this can be solved by multiplying them by such numbers so that the number of electrons i.e. charges, equal in both equations:
5(Sn2+ --> Sn4+ + 2e-)
2(8H+ + MnO4^- + 5e- --> Mn2+ + 4H2O)
------------------------ -------------------------- -----------------
The overall equation becomes:
16H+ + 5Sn2+ + 2MnO4^- --> 5Sn4+ + 2Mn2+ + 8H2O
Now you just have to use the molar ratios, like we use in chemical equations
No. of mol of SnCl2= 9.5/ 190
=0.05
since 5 mol of Sn2+ produce >>>2 mol of Mn2+
and 1 mol produce >>>>>>>>>>2/5 mol of Mn2+
similarly 0.05 mol produce >>>>>2/5 x 0.05
=0.02 mol