Question

X forms an ionic compound with the formula

XCI, which has an M, of 74.5. What is the M₁ of
the oxide of X?
A 55
B 71
C 87
D 94

Answer 1

94 g/mole

Step-by-step explanation:

The following answer assumes M is molar mass (g/mole):

One mole of Cl is 35.45 grams. Since 1 mole of MCl is 74.5 grams, one mole of M will be (74.5-35.45 = ) 39.05 grams/mole. This just so happens to be the molar mass of potassium, K. That would mean the compound could be KCl.

We learn from this that M has a single bond. The oxide of M must take into account the fact that oxygen makes 2 bonds per atom. That would mean that M ocxide would have the formula M2O. There are two M's per O.

M2O would have a molar mass of (2x39.05) + 16 = 94.1 g/mole