The MOLECH 11

Mole (mol)

• SI base unit used to measure the amount of a substance

• One (1) mole of anything is 6.02 X 1023

• Compare to other counting units:– Pair = 2– Dozen = 12– Gross = 144– Ream = 500– Mole = 6.02 X 1023

Math Practice

• How many gloves are there in 8 prs?

• How many roses in 2.5 doz?

• How many atoms in 0.5 mol?

Avogadro’s Numberis

6.02 X 1023

• Amedeo Avogadro determined the volume of one mol of gas

Molar Mass

• The mass in grams of one mole of any pure substance

• Numerically equal to its atomic mass (amu) but, has the units g/mol

• Example: – An atom of manganese has a mass of

54.94 amu– A molar mass = 1 mol of manganese – 54.94 g of Mn contains 6.02 X 1023 atoms of

Mn

Molar Mass

• Ionic Compounds

• Use the formula mass

• Example: – Sodium Chloride– A mole of sodium has mass = 22.99 g– A mole of chloride ions has mass = 35.45 g – One mole of NaCl = 58.44 g– Or, the molar mass of NaCl is 58.44 g/mol

What is the molar mass of potassium nitrate?

Molar Mass

• Of a metal

• Use the atomic mass converted to g/mol

• Example: – Iron– A mole of iron has mass = 55.84 g– One mole of Fe = 55.84 g– Or, the molar mass of iron is 55.84 g/mol

Practice

• What mass of aluminum foil will contain an Avogadro’s number of Al atoms?

• An experiment calls for 0.250 mol of Al. How much should be weighed out?

Molar Mass of Nonmetallic Elements

• Use the mass of 6.02 X 1023 molecules

• What is the molar mass of:– A. hydrogen– B. nitrogen– C. oxygen

Molar Mass of Molecules

• What is the molar mass of water?• A mol of water molecules contains

– _____ mol of H atoms– _____ mol of O atoms

The molar mass of water is ______________

Calculations with Moles

a. Counting mol if given the mass

• Ex. How many moles of calcium are there in a 16.0 g sample?

• Track Method:

=

Calculations with Moles

a. Counting mol if given the mass

• Ex. How many moles of calcium are there in a 16.0 g sample?

• Track Method:

16.0 g Ca

= mol

Calculations with Moles

a. Counting mol if given the mass

• Ex. How many moles of calcium are there in a 16.0 g sample?

• Track Method:

16.0 g Ca 1 mol Ca

40.1 g Ca = mol

Calculations with Moles

a. Counting mol if given the mass

• Ex. How many moles of calcium are there in a 16.0 g sample?

• Track Method:

16.0 g Ca 1 mol Ca

40.1 g Ca = 0.399 mol

Calculations with Moles

b. Relating mass to number of particles

• Ex. What is the mass of 2.50 X 1021 calcium atoms?

• Track Method:

2.50 X 1021 atoms

= g Ca

Calculations with Moles

b. Relating mass to number of particles

• Ex. What is the mass of 2.50 X 1021 calcium atoms?

• Track Method:

2.50 X 1021 atoms 40.1 g Ca

6.02 X 1023 atoms

= g Ca

Calculations with Moles

b. Relating mass to number of particles

• Ex. What is the mass of 2.50 X 1021 calcium atoms?

• Track Method:

2.50 X 1021 atoms 40.1 g Ca

6.02 X 1023 atoms

= 0.166 g Ca