ANSWER TO QUESTION 2

Question:

Calculate how much iron (II) chloride we need to get a 2.5 ml, 2 molar solution of iron (II).

Calculate how much iron (III) chloride we need to get a 10 ml, 1 molar solution of iron (III).

Help: (Molecular weight of iron(II)chloride tetrahydrate is 198.1 g/mol)

Answer:

For 1 L, 1 molar iron (II) chloride solution we need 2 mol iron chloride.

For 2.5 mL we need 0.005 mol iron chloride.

2 mol is 396.2 g ==> 0.005 mol is 0.005 mol * 198.1 g/mol = 0.9905g

We have to weigh 0.9905 g (~1 g) iron (II) chloride in 10 ml of water. Instead of using water we use here a 1 molar solution of hydrochloric acid.

Because Fe(II) always tends to get oxidized, most synthesis approaches take more iron (II) ions than is stochiometrically needed.

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