Question

Jodi reacts 6.087 grams of cobalt (mw=58.933) with a solution containing excess gold (iii) chloride and recovers 13.572 g of solid gold (mw=196.967). Which reaction, 1 or 2, most likely occurred in their experiment?

Answer 1

The correct answer is reaction 2 most likely occurred in their experiment.

So the given two reactions are as follows:

1) Au³⁺(aq) + Co(s) --> Au(s) + Co³⁺(aq)

2) 2Au³⁺(aq) + 3Co(s) --> 2Au(s) + 3Co³⁺(aq)

Mass of Co = 6.087 g

Molar mass of Co = 58.933 g/mol

Moles of Co =
`(6.087 g)/(58.933 g/mol)` = 0.1032

Mass of Au = 13.572 g

Molar mass of Au = 196.967 g/mol

Moles of Au =
`(13.572 g)/(196.967 g/mol)` = 0.069

Now based on reaction 1) the molar ratio between Co and Au is 1:1

So as per this reaction 0.1032 moles of Co would produce 0.1032 mole of Au

Again based on reaction 2) the molar ratio between Co and Au is 3:2

So as per this reaction 0.1032 moles of Co would produce
`(2 x 0.1032)/(3)` mole of Au

or, As per the second reaction 0.1032 moles of Co would produce 0.0688 moles of Au