Question

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

Answer 1

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

Answer 2

Answer:

$7.08*10^{22}$ formula units

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 = $\frac{mass}{molar mass}=\frac{11.2g}{95.211g/mol}= 0.117633mol$

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=$0.117633 mol*6.022*10^{23} formula units/mol =7.08*10^{22} formula units$