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Date November 2016 Marks available 1 Reference code 16N.3.sl.TZ0.4
Level SL Paper 3 Time zone TZ0
Command term Calculate Question number 4 Adapted from N/A

Question

A student wanted to determine the formula of indium sulfate. She applied an electrical current of 0.300A to an aqueous solution of indium sulfate for 9.00 × 10s and found that 1.07 g of indium metal deposited on the cathode.

Calculate the charge, in coulombs, passed during the electrolysis.

\(\left( {{\text{current }}I = \frac{{{\text{charge }}Q\,}}{{{\text{time }}t}}} \right)\)

[1]
a.

Calculate the amount, in mol, of electrons passed using section 2 of the data booklet.

[1]
b.

Calculate the mass of indium deposited by one mole of electrons.

[1]
c.

Calculate the number of moles of electrons required to deposit one mole of indium. Relative atomic mass of indium, Ar=114.82.

[1]
d.

Deduce the charge on the indium ion and the formula of indium sulfate.

[1]
e.

Markscheme

«0.300A × 9.00 × 103 s =» 2.70 × 103 «C»

a.

«mol e = \(\frac{{2700\,{\text{C}}}}{{96\,500\,{\text{C}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\) =» 2.80 × 10−2 «mol»

b.

«\(\frac{{1.07{\rm{g}}}}{{0.0280{\rm{mol}}}}\)=» 38.2 «g»

c.

«\(\frac{{114.82\,{\text{g}}}}{{38.2\,{\text{g}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\) e =» 3.01/3.00 «mol e»

d.

In3+ /3+ AND In2(SO4)3

Do not accept “+3/3”

e.

Examiners report

[N/A]
a.
[N/A]
b.
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c.
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d.
[N/A]
e.

Syllabus sections

Options » A: Materials » A.2 Metals and inductively coupled plasma (ICP) spectroscopy
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