Conversions involving molar mass and Avogadro’s number.

Conversions involving molar mass and Avogadro’s number

A unit of measurement for counting atoms or molecules

1 Mole = 602 billion trillion 602,000,000,000,000,000,000,000 6.02 X 1023 (this is known as Avogadro’s

number)

Avogradro’s number is named in honor of Amedeo Avogadro (1776 – Amedeo Avogadro (1776 – 1856)1856)

He studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

We can count anything using the mole Example:

▪ 1 mole of M & M’s would stretch from here to the sun and back 200 billion times▪ * assuming m&m’s are 1 cm in diameter and the distance to the sun is 93

million miles

▪ Can you swim in1 mole of water?▪ 1 mole of H2O= about 1/3 of a cup (18 mL)

It is helpful in counting a large number of items

If the items are extremely small

= 6.02 x 1023 C atoms

= 6.02 x 1023 H2O

molecules= 6.02 x 1023 NaCl formula unit

1 mole C

1 mole H2O

1 mole NaCl

* 1 mole = 6.02 x 1023 particles

Note: Particles could refer to atoms, molecules, formula units

* 1 mole = molar mass (g) of compound being used

MUST use dimensional analysis

MUST use the molar mass if grams are used in the problem

Be able to convert from Moles to atoms or molecules Moles to grams Grams to moles

How many atoms are in 0.500 mole of Al? Setup your problem using dimensional analysis:

* Multiply across and divide by the number at the bottom

0.500 mol Al

1 mol Al

6.02 x 10 23 atoms Al= 3.01 x 10 23

atoms Al

How many moles of Sulfur (S) are in 1.8 x 10 24 atoms of sulfur ? (Use dimensional analysis)

* Multiply across and divide by the number at the bottom

1.8 x 10 24 atoms S

6.02 x 10 23 atoms S

1 mol S= 2.99 mol S

1.) How many moles are in 5.22 x 10 24 atoms of H2O?

2.) How many molecules of NaOH are in 23 moles of NaOH?

How many grams are in 2.34 moles of Sodium hydroxide? You will utilize the molar mass you calculated and use

dimensional analysis.

2.34 mol NaOH

1mol NaOH

40.00 grams NaOH= 93.60 grams

NaOH

Molar mass of NaOH

How many molecules are in 42 grams of NaOH? Avogadro’s number: (6.02 x 1023 atoms, molecules or formula

units )= 1 mole)

42 grams NaOH

40.00 grams NaOH

1 mole NaOH

1 mole NaOH

6.02 x 1023 molecules NaOH

= 6.32 x 10 23 molecules NaOH

Molar mass of NaOH

1.) Determine the molar mass for Barium Hydroxide.

2.) How many moles are in 25.00g of barium hydroxide?

3.) How many grams are in 6.7 moles of barium hydroxide?

4.) How many formula units are in 35.00g of barium hydroxide?

5.) How many molecules are in 4.5 moles of barium hydroxide?