Identity of metal from electrolysis

[TT0]

Homework Statement

A solution of a trivalent metal ion is electrolysed by a current of 5.0A for 10 minutes during which time 1.18g of metal was plated out. The identity of the metal is:

A cobalt
B chromium
C indium
D gallium
E bismuth

Relative atomic masses:
1 faraday = 96,486 coulombs.

Homework Equations

current*time=coulombs
coulombs/96486=faraday
1 faraday = 1 mol of electrons

The Attempt at a Solution

5.0*10*60=3000 coulombs
3000/96486=0.031092 mol of electron

Since trivalent metal ion, mol of metal = 0.031092/3 = 0.010364 mols

Trial and error by dividing 1.18 by molar mass shows indium is closest. 1.18/114.82 = 0.1028. Is this the correct answer?

Cheers!

 

[Borek]

Yes, indium sounds good.

 

[TT0]

Thanks!

 

[jimseiton]

To avoid trial and error use this formula:

Molar mass (g/mol)=mass(g)/number of moles(mol)
M=m/n
M= 1.18g/ 0.010364 mol
M=113.86 g/mol

Cd
113.86-112.41=1.45 difference
Indium
114.82-113.86=0.96 difference

So the closest answer is Indium