11 29 how many moles part ii

Launch: 11/30   Grab your binder and immediately take a seat!

  Place homework (practice questions), binder paper, and a pen/pencil on your desk.

Today’s Objective: I can convert between grams and moles using molecular mass as a conversion factor

Tonight’s HW: Finish practice question worksheet

Launch 11/30

1.  Calculate the molecular mass of H2 (include units!).

Launch 11/30

2.  Calculate the molecular mass of NO3 (include units!).

Launch 11/30

3.  Calculate the molecular mass of Mg(ClO2)2 .

Announcements   Quiz on Friday

  The mole   Conversions

  Unit exam in 2 weeks

  Block 5 earned the party this Friday

How many moles? - Part II Mr. Heffner 11/30/09

How many moles?   Molar mass

  used to convert between grams and moles   units = grams/mole

  can be shown as a fraction

Molar mass of H2 = 2.02 g/mol

2.02 grams 1 mole

1 mole 2.02 grams

or

How many moles?   There is a 3-step process:

1.  Write down the starting unit. 2.  Calculate molecular mass and turn it into a

conversion factor with the starting units on the bottom.

3.  Cancel units and multiply across the top and bottom.

Example #1: mol g How many grams of H2 are there in 2 moles of H2?

  Step #1: Write down the starting unit.

2 moles

How many grams of H2 are there in 2 moles of H2?

  Step #2: Calculate molecular mass and turn it into a conversion factor with the starting units on the bottom.

2.02 grams 1 mole

Example #1: mol g

2 moles X =

How many grams of H2 are there in 2 moles of H2?

  Step #3: Cancel units and multiply across the top and bottom.

2.02 grams 1 mole

Example #1: mol g

2 moles X =2 X 2.02 grams

1

= 4.04 grams

units!

Example #2: g mol How many moles of CO are there in 14.00 grams of CO?

  Step #1: Write down the starting unit.

14.00 grams

How many moles of CO are there in 14.00 grams of CO?

  Step #2: Calculate molecular mass and turn it into a conversion factor with the starting units on the bottom.

1 mole 28.01 grams

Example #2: g mol

14.00 grams X =

How many moles of CO are there in 14.00 grams of CO?

  Step #3: Cancel units and multiply across the top and bottom.

1 mole 28.01 grams

Example #2: g mol

14.00 grams X =14.00 X 1 mole

28.01

= ~.5 moles

units!

Partner Teaching   Partner A teaches Partner B

  Partner A writes and narrates   Partner B listens

  Partner B completes the problem on own paper

  Switch!

1.  How many moles of O2 are there in 64.00 grams of O2?

2.  How many grams of NO2 are there in 4 moles of NO2?

Foldable   Define the following terms:

  Mole   Avogadro’s number

  Molecular mass   Conversion factor   Starting unit

Practice Questions   Practice question worksheet

Exit Slip 1.  What is the molar mass of Al(OH)3?

a.  43.99 g/mol b.  78.01 g/mol

c.  300.03 g/mol d.  303.00 g/mol

Exit Slip 2.  Which of the following is not a correct way to

represent the molecular mass of CH4?

a. 

b. 

c. 

d.  16.05 g/mol

1 mole 16.05 grams

16.05 grams 1 mole

16.05 moles 1 gram

Exit Slip 3.  Which of the following shows the correct way to

calculate the number of moles in 16.00 grams of O2?

a.  16.00 moles X

b.  16.00 grams X

c.  16.00 grams X

d.  16.00 moles X

32.00 grams 1 mole 1 mole

16.00 grams 1 mole

32.00 grams

16.00 grams 1 mole

Exit Slip 4.  How many grams of NH3 are there in 2 moles of NH3?

a.  1.00 moles b.  14.01 grams

c.  17.04 grams d.  34.08 grams

Exit Slip 5.  How many moles of N2 are there in 14.01g of N2?

a.  .5 moles b.  2 mole

c.  14.01 moles d.  28.02 moles

Homework   Finish practice questions