How many grams of O are in 645 g of Li_2 O? You have purified a new protein and

Question

How many grams of O are in 645 g of Li_2 O? You have purified a new protein and find that it contains 0.143 percent Zn. Assuming that there are two atoms of zinc per molecule of protein, what is the molar mass of the protein? A certain protein was found to contain 0.413% cobalt by mass. Determine the minimum molecular mass of the protein. Some of the formulas below could be either molecular or empirical formulas; however, some could only be molecular formulas. Which of the following formulas must be molecular formulas? Select all that apply.

Explanation / Answer

Molar Mass of Li2O is 29.88 g/mol.

Atomic Mass of Oxygen is 15.99 g/mol.

So, 29.88 g of Li2O contains 15.99 g of Oxygen.

So, mass of Oxygen in 645 g of Li2O is 645 g * (15.99/29.88) = 345.16 g.

The protein molecule contains at least one Cobalt atom.

Atomic Weight of Cobalt is 58.93 g/mol.

Mass % of Cobalt is 0.413 %.

So, minimum molar mass of the protein is (58.93 g/mol) * (100/0.413) = 14268.77 g/mol

The protein molecule contains two Zinc atoms.

Atomic Weight of Zinc is 65.38 g/mol.

Mass % of Zinc is 0.143 %.

So, minimum molar mass of the protein is (2* 65.38 g/mol) * (100/0.143) = 91440.56 g/mol

C2H4O2 and C8H10N4O2 are surely molecular formulas. These formulas could further be reduced to simpler formulas. So, these are not empirical formulas.

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