Question

The total particle concentration in 100 cm3 of 0.2 M Al2(SO4)3 solution is

Answer 1

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Write the equation for aluminium sulfate's dissociation (all the species are in aqueous solution)

Al2(SO4)3⇌2Al3++3SO2−4

Notice the 1 mole of aluminium sulfate produces

2

moles of aluminium cations and

3

moles of sulfate anions.

This means that, for a given volume of solution, the concentration of the sulfate anions will be three times larger than the concentration of aluminium sulfate.

Think of it like this - same volume, three times the number of moles in favor of the sulfate anion

→

3 times the concentration.

Thus,

CAl2(SO4)3=13⋅CSO2−4=13⋅0.22 M=0.073 M