CHEMISTRY

Feb 22, 2011

Warm Up

Find the molar mass of these substances Fe3N2

Mg(OH)2

Agenda

Warm Up Unit 8 Notes

Intro to Moles and Stoichiometry Practice Problems Homework

Unit 8 Worksheet 1 Reminder:

Test Make Up Wednesday, Thursday, or Friday ONLY

Are these moles?

What is a mole?

A unit of measurement

Since the numbers in chemistry are so small, we use a “preferred unit of measurement” (mole) to represent the small number

What are the units of measurement? "that equal number" of atoms randomly chosen.

the number of atoms in the atomic weight in g of any element.

the number of atoms in 16 g of oxygen, in 4 grams of He, in 32 g of sulfur, etc.

the number of molecules in the molecular weight, in grams, of any compound.

the number of molecules in 18 g of water, in 40 g of lithium carbide.

Much later, a mole, that equal number, was found to be 6.022 x 1023(representative particles).

Examples

1 mole (or abbr. mol) = 12.011 g of Carbon

1 mol of Carbon = 6.02 x 1023 atoms of C

1 mol of H2O = 6.02 x 1023 molecules of water

1 mol of NaCl = 6.02 x 1023 units of NaCl

Copyright © Houghton Mifflin Company.All rights reserved. 8–5

Figure 8.1: All these samples of pure elements contain the same number (a mole) of atoms: 6.022 x 1023 atoms.

Moles in mass

1 mole can equal the atomic weight of an element. 1mol of C = 12.011g of C

1 mole can equal the atomic weight of a compound 1mol of CO = 12.011g of C + 15.99 g of O

= 28.0 g of CO

Practice Problems

How many grams of Cu are in 1.20 mol of Cu?

How many moles are in 70g of Cl?

Moles in compounds

Let’s say you have water aka. H2OHow many moles of Hydrogen atoms(ions) are

in water? Ask yourself how many individual atoms of

Hydrogen do you see in water? Did you say 2??? Is that your final answer? You are correct! So how many mols of

Oxygen atoms do you see?

Moles in an equation

2 H2 + O2 2H2O

How many moles of Hydrogen molecules are in the reactants?

*Coefficients serve as the number of moles too!

Therefore, there are 4 mols of Hydrogen gas

NOPE!!!! Fooled you.. 2 mols of Hydrogen gas

Molecules

Atoms

Units Mole Conversion

Boomerang

Mole Conversions

Mass to mole or vice versa: How many moles are in 24 g of Carbon? Look at the boomerang:

Start with the given: 24 g (mass) of C What do you want in the end? Moles of C Use the conversion factor given:

1 mole

Atomic mass

24 g of C x 1 mol of C = 2.0 mol of Carbon

12.011 g of C

White Boards

Given 200 g of water, how many mols of water do you have?

How many grams of carbon monoxide are in 1.5 mols of carbon monoxide?

More conversion

Mole to atoms/molecules/particles or vice versa How many atoms are in 2.00 mols of Carbon? Look at the boomerang:

Where do you begin? (the given: mols) What do you need in the end? (atoms: particles)

What’s the conversion factor? 6.02 x 1023 Atoms of C

1 Mols of C

2.00 mols of C x 6.02 x 1023 atoms of C = 1.20 x 1024 atoms C

1 mol of C

White boards

How many molecules of oxygen gas are in 3.0 mols of Oxygen gas?

How many mols of Oxygen gas are in

4.67 x 1024 molecules of Oxygen gas?

More conversion

Mole to volume of gas or vice versa What is the volume occupied by 2 mols of hydrogen gas? Look at the boomerang:

Where do you begin? (the given: mols) What do you need in the end? (volume of gas)

What’s the conversion factor? 22.4 L of H2

1 Mols of H2

2.00 mols of H2 x 22.4 L of H2 = 44.8 L of H2 1 mol of H2

White boards

Convert 4.38 moles of He to liters Convert 3.01 L of N to moles

Practice

Must show work (dimensional analysis) How many grams are in 1 mol of Mercury? Given a 1.5 mols of carbon dioxide, how

many molecules of carbon dioxide do you have?

Homework

Mole Conversion Worksheet 1