Question

How many formula units make up 12.8 g of magnesium chloride (MgCl2)? Express the number of formula units numerically.

Answer 1

Answer:

8.09 × 10²² formula units

Explanation:

Mass of MgCl₂ is 12.8 g

Required to calculate the formula units

1 mole of a compound contains the Avogadro's number formula units

That is;

1 mole = 6.022 × 10²³ formula units

Step 1: Calculate the moles of MgCl₂ in 12.8 g

The molar mass of MgCl₂ is 95.211 g/mol

Number of moles = Mass ÷ molar mass

Moles of MgCl₂ = 12.8 g ÷ 95.211 g/mol

                          = 0.1344 mole

Step 2: Calculate the formula units of MgCl₂

1 mole =  6.022 × 10²³ formula units

Therefore;

Number of formula units = Moles × 6.022 × 10²³ formula units

                                    = 0.1344 mole × 6.022 × 10²³ formula units

                                     = 8.09 × 10²² formula units

Therefore, there are 8.09 × 10²² formula units in 12.8 g of MgCl₂