Physical Science Ms. Cilli December ½, 2011. While we wait, review conversion factors.

Describing Reactions: Counting Atoms

Physical Science

Ms. Cilli

December ½, 2011

While we wait, review conversion factors

Objectives• Convert between moles and mass of a

substance using molar mass.

• Calculate amounts of reactants or products by using molar mass, mole ratios, and balanced chemical equations.

How many eggs?

How many eggs?

How many eggs?

THE MOLE

• A mole (abbreviate mol) is an amount of substance that contains 6.02 x 1023 particles

• One mol of eggs contains 6.02 x1023 eggs

or • 602,000,000,000,000,000,000,000 eggs

Molar Mass

• The mass of one mole of a substance is the molar mass

• Molar mass is the same as atomic mass, just different units

• Carbon has an atomic mass of 12.0 amu, it has a molar mass of 12.0 grams

Conversion Factor

1 mol element = x grams element

X is the molar mass for the element

Where do you find the molar mass again?

Find the conversion factors for

converting between grams and moles:

• Moles to grams of Au

• Grams to moles of Na

• Grams to moles of C

• Moles to grams of Ni

Molar Masses of Compounds

• To calculate the molar mass of a compound, you add up all the molar masses of each atom

• Examples:– O2 = 15.99 g + 15.99 g = 31.98g

– CH4 = 12.01 g + 1.01 g + 1.01 g + 1.01 g + 1.01 g = 16.05g

– CO2 =

Conversion factor

1 mole= g mass of cmpd

Review for Conversion Factors

Watch this…

• Convert 35.6g Au to moles– What is the conversion factor?

Help me…

• How many grams are in 6.82 moles of Na?– What is the conversion factor?

Your turn…

• How many moles are in 68.94 g of C?– What is the conversion factor?

Watch…

• How many grams are in 9.45 moles of Al2O3?

– Mass of Al2O3 = 101.96 g/mol

– CF: 1 mole=101.96g Al2O3

9.45 moles Al2O3

1 mole

101.96 g Al2O3= 963.52 g Al2O3

Another one…

• How many moles are in 0.370 g BrO2?– What is the conversion factor for the

cmpd?

On your own…

• How many grams are in 2.50 mol KCl?

• How many moles are in 75.0g of dinitrogen trioxide?

How much oxygen?

2H2 + O2 2H2O

• How much oxygen do we need to make 144 grams of water?1. Find the molar mass

2. Convert from 144 grams H2O to moles H2O

3. Use mole ratio to go from moles H2O to moles O2

How much oxygen?

2H2 + O2 2H2O

• How much oxygen do we need to make 144 grams of water?1. Find the molar mass

2. Convert from 144 grams H2O to moles H2O

3. Use mole ratio to go from moles H2O to moles O2

Closure

• When doing mole conversions, you use the ______ for the element or compound.

A. Molar mass

B. Atomic number

C. Atomic mass

D. All of these

T/Th Assignment: MWF

• Independent Work:– Read pages 190-205 – Answer the review questions– Work on the study guide

• Homework:– Section 7.1b Assignment due Friday,

December 2nd by 8PM

MWF Assignment: TTH

• Independent Work:– Read pages 190-205 – Answer the review questions– Work on the study guide

• Homework:– Section 7.1 Assignment due Monday,

December 5th by 8AM

Yes, you will need to complete it over the weekend and have it turned in Monday morning