Question

How many formula units make up 11.2 g of Magnesium Chloride MgCl2?

Answer 1

`7.08*10^(22)` formula units

Step-by-step explanation:

The first step in solving this question is to find the number of moles of magnesium chloride in 11.2 g.

number of moles =
`(mass)/(molar mass)=(11.2g)/(95.211g/mol)= 0.117633mol`

The second step is to remember Avogadro's number. In one mole of magnesium chloride, there are 6.022*10²³ formula units. So how many formula units are there in 0.117633 moles?

no. of formula units=
`0.117633 mol*6.022*10^(23) formula units/mol =7.08*10^(22) formula units`

Answer 2

Solved:
Molar mass MgCl2 = 24.31 + 35.45 x 2 = 95.21g/mol
One mole is equal to 6.022*10^23 formula units
Each mole of MgCl2 has 6.022 x 10²³ MgCl2 molecules (formula units)

so number of formula units in the MgCl2 sample =
11.2 g MgCl2 * [1 mol / 95.21 g] x [6.022 x 10²³ formula units / mol]

= 7.0 x 10^22 MgCl2 formula units