Question

A newly discovered metalloprotein, which contains three atoms of Mg per molecule of protein, is found to be 0.715% Mg by mass. Calculate the molar mass of the metalloprotein in g/mol.

Hint: Another way of expressing that the metalloprotein is 0.715% Mg by mass is to say that 100 g of the metalloprotein contains 0.715 g of Mg. Start by determining the number of moles of Mg per 100 g of the metalloprotein.

Answer 1

Assume you have 100 g of the protein. Any number gives you the same answer by the way

mass of Magnesium = 0.715 g = 0.715 g / 24.305 g/mole = 0.02942 moles Mg

Since each molecule of the protein has 3 magnesium atoms, each mole of the protein has 3 moles of Mg

moles of protein = 0.02942 / 3 moles = 0.0098 mole

molar mass of protein = mass / moles = 100g / 0.0098 mole = 10204.1 g/mol

molar mass of the metalloprotein in g/mol = 10204.1 g/mol

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