What is the molecular formula of a compound that is composed of 0.0722 g Cr and 0.148 g Cl that has a molar mass of 158 g/mol?

Question

Quizplus · Accepted Answer

First, we need to convert the given masses of Cr and Cl to moles using their molar masses (52 g/mol for Cr and 35.5 g/mol for Cl):
0.0722 g Cr / 52 g/mol = 0.00139 mol Cr
0.148 g Cl / 35.5 g/mol = 0.00418 mol Cl
Next, we need to find the ratio of Cr to Cl in the compound by dividing each mole value by the smaller of the two (in this case, 0.00139 mol):
0.00139 mol Cr / 0.00139 mol = 1
0.00418 mol Cl / 0.00139 mol = 3
So the molecular formula should have one Cr atom and three Cl atoms, giving us CrCl3. To check if this is the correct formula, we need to calculate its molar mass:
1(52 g/mol) + 3(35.5 g/mol) = 158.5 g/mol
The calculated molar mass is close enough to the given molar mass (158 g/mol) to confirm that CrCl3 is the correct formula. Therefore, the answer is B.

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