Counting Atoms/The Mole

Vocabulary

100

What does amu stand for?

Atomic Mass Unit.

200

What is Avogadro's number?

6.022 x 10^23.

300

1 amu=?

1.66 x 10^-24g.

400

Scientists have defined this as a much smaller unit for mass.

AMU or atomic mass unit.

500

What is average atomic mass?

The average mass of atoms of an element.

Counting Atoms

100

Can we count identical elements by weighing them?

Yes.

200

When we are counting, the objects or elements behave as thought they are all __________.

Identical.

300

What is the average atomic mass for O?

16.00 amu.

400

Calculate the mass, in amu, of a sample of Copper that contains 25 atoms.

1,589 amu.

500

Calculate the number of lithium atoms that are present in a sample that has a mass of 315 amu.

45.38 Li atoms.

The Mole

100

True or False. One mole of something consists of 1.66 x 10^-24 units of that substance.

False. One mole=6.022 x 10^23.

200

True or False. Atoms and Moles are the same thing.

False.

300

1 mol Cl= 35.45 g Cl.

What is an equivalent statement or molar mass?

400

True or False. The mass of 1 mol of an element is equal to its average atomic mass in grams.

What is true?

500

When you are doing conversion factors, what is the number one thing that you need to make sure of before you start multiplying or dividing numbers?

That your units cancel out.

Mole Calculations

100

How many moles are in 15. 0 g of N?

1.071 moles.

200

How many grams does 27 moles of O weigh?

432 g.

300

How many moles are in 35.24g of calcium?

.87924 mol Ca.

400

How many grams does 173 moles of boron weigh?

1,870 g.

500

In 78.20 g of potassium, there are ________ potassium atoms present.

1.204 x10^24 atoms.