Question

How many moles are equal to 89.23g of aluminum chloride, AlCl3?

Answer 1

`\boxed {\boxed {\sf 0.6692 \ mol \ AlCl_3}}`

Step-by-step explanation:

To convert from grams to moles, we must use the molar mass. This can be calculated using the Periodic Table.

1. Molar Mass

First, identify the elements in the compound AlCl₃. They are aluminum and chlorine. Now find the masses:

• Al: 26.981538 g/mol
• Cl: 35.45 g/mol

Take a look at the compound. There is a subscript of 3 after chlorine, so we must multiply its molar mass by 3 then add aluminum's.

• AlCl₃= 3(35.34 g/mol) + 26.981538 g/mol = 133.331538 g/mol

2. Convert Grams to Moles

We can use the molar mass as a ratio.

`(133.331538 \ g \ AlCl_3)/(1 \ mol \ AlCl_3)`

Multiply by the given number of grams: 89.23

`89.23 \ g \ AlCl_3 * (133.331538 \ g \ AlCl_3)/(1 \ mol \ AlCl_3)`

Flip the fraction so the grams of aluminum chloride cancel out.

`89.23 \ g \ AlCl_3 * (1 \ mol \ AlCl_3)/(133.331538 \ g \ AlCl_3) = 89.23 \ * (1 \ mol \ AlCl_3)/(133.331538)`

`(89.23 \ mol \ AlCl_3)/(133.331538)`

`0.6692340112 \ mol \ AlCl_3`

3. Round

The original measurement of grams has 4 significant figures. We must round to 4 sig figs.

For the number we calculated, that is the ten thousandth place.

The 3 in the hundred thousandth place tells us to leave the 2.

`0.6692 \ mol \ AlCl_3`

There are about 0.6692 moles of aluminum chloride in 89.23 grams.