How many formula units make up 10.2 g of magnesium chloride (MgCl2)?

6.46×10²² formula units

Explanation:

From the question given above, the following data were obtained:

Mass of MgCl₂ = 10.2 g

Number of formula units =?

From Avogadro's hypothesis,

1 mole of MgCl₂ = 6.02×10²³ formula units

But,

1 mole of MgCl₂ = 24 + (35.5×2) = 24 + 71 = 95 g

Thus, we can say:

95 g of MgCl₂ = 6.02×10²³ formula units

Finally, we shall determine the formula units in 10.2 g MgCl₂. This can be obtained as follow:

95 g of MgCl₂ = 6.02×10²³ formula units

Therefore,

10.2 g of MgCl₂ = (10.2 × 6.02×10²³) / 95

10.2 g of MgCl₂ = 6.46×10²² formula units

Thus, 10.2 g of MgCl₂ contains 6.46×10²² formula units