Mole Calculations 1

Chemical Calculations Atoms and molecules are extremely small. If they are so small and so light, how can we weigh them? We weigh large numbers of them.

Avogadro took 1.00 g of the smallest atom (H) and determined how many H atoms there are in 1.00 g of H. He found that: 1.00 g H = 6.02 x atoms = 1.00 mole This is called Avogadro’s number

1 dozen donuts = 12 donuts 1 century = 100 years 1 millennium = 1000 years 1.00 mole = 6.02 x particles

The mole is a large number of particles Particle AtomelementCu 6.02 x at 1 mole MoleculecovalentCH x molecules 1 mole Formula UnitionicNaCl 6.02 x FUs 1 mole

1. Convert 2.5 x at C to moles = 42 moles C 6.02 x at x 1 mole2.5 x at

2. Convert 16.3 moles CO 2 to molecules = 9.81 x molecules 1mole x 6.02 x molecules16.3 moles

3. Convert 8.9 x molecules CO 2 to moles = 15 moles CO x molecules x 1 mole 8.9 x molecules

= 1.7 x FUs 1mole x 6.02 x FU 28 moles 4. Convert 28 moles NaCl to Formula Units

Determining Avogadro’s Number

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Determining Avogadro’s Number Produce a volume of hydrogen gas while measuring the time and electrical current. Volume of H mL Time80.7 s Current0.913 amp

Background information 1 amp is defined as the number of coulombs per second. There are 6.24 x electrons in a coulomb. The density of H 2 is g/L. It takes 1 electron to make 1 H atom

1. Calculate the number of atoms of H, starting with the time. = x at 1 el x 1 at H 1 couls x 6.24 x elx coul80.7 s

2. Calculate the number of grams H starting with the volume of H. = x g H 1 L x g 1000 mL x 1 L10.0 mL

3. Divide the atoms of H by the grams of H to get the number of H atoms in a gram which is Avogadro’s number x g H =5.84 x at/ 1 gram H =5.84 x at/ 1 mole The Mole Song x at Avogadro Facts