12 1 How Many Atoms

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Launch: 12/1   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 moles and atoms using Avogadro’s number as a conversion factor

Tonight’s HW: Finish the back of the practice question worksheet

Launch 12/1 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

Launch 12/1 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

Announcements   Quiz on Friday

  The mole   Conversions

  Unit exam in 2 weeks

How many atoms? Mr. Heffner 12/1/09

Review: 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

How many atoms?   Avogadro’s number…

  is equal to 6.02 X 1023 atoms/mol   can be used to convert between moles and atoms

6.02 X 1023 atoms 1 mole

1 mole 6.02 X 1023 atoms

..or particles, or molecules

How many atoms?   There is a 3-step process for conversions:

1.  Write down the starting unit. 2.  Write the conversion factor with the starting units on

the bottom. 3.  Cancel like terms and multiply across the top and

bottom.

Example #1 How many atoms are there in 2 moles of carbon (C)?

  Step #1: Write down the starting unit.

2 moles

How many atoms are there in 2 moles of carbon (C)?

  Step #2: Write conversion factor with the starting units on the bottom.

Example #1

2 moles X =

How many atoms are there in 2 moles of carbon (C)?

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

Example #1

2 moles X =2 X 6.02 X 1023 atoms

1 = 12.04 X 1023 atoms

Ignore

= 1.204 X 1024 atoms

Example #2 How many atoms are there in 1.5 moles of CO2?

1.5 moles

How many atoms are there in 1.5 moles of CO2?

Example #2

1.5 moles X =

How many atoms are there in 1.5 moles of CO2?

Example #2

1.5 moles X =1.5 X 6.02 X 1023 atoms

1 = 9.03 X 1023 atoms

Ignore

Example #3 How many moles are there in 3.01 X 1023 molecules of CO2?

3.01X1023 molecules

How many molecules are there in 1.5 moles of CO2?

1 mol 6.02X1023 molecules

Example #3

3.01X1023 molecules X =

How many molecules are there in 1.5 moles of CO2?

1 mol 6.02X1023 molecules

Example #3

3.01X1023 molecules X =3.01 X 1 mol

= .5 mol

Whiteboards   Work in pairs

  Trade-off marker every question

  You have 60 seconds to solve the question   Show all of your work!   Don’t forget units!

  Lift board only when prompted

How many atoms are there in 1 mole of potassium (K)?

How many molecules are there in .5 moles of HCl?

How many moles of NO are there in 9.03 X 1023 particles?

How many moles of fluorine (F) are there in

12.04 X 1023 atoms?

Practice Questions   Practice question worksheet

Exit Slip 1.  What is Avogadro’s number?

a.  6.02 X 1024 atoms b.  6.02 X 1023 atoms

c.  3.01 X 1023 atoms d.  1.2 X 1024 atoms

Exit Slip 2.  Which of the following shows the correct way to

calculate the number of atoms in 2 moles of O2?

a.  16 moles X

b.  2 moles X

c.  2 moles X

d.  2 moles X

32.00 grams 1 mole

1 mole 16.00 grams

1 atoms 6.02 X 1023 moles

Exit Slip 3.  How many atoms of sodium (Na) are in 1 mole?

a.  3.01 X 1023 atoms b.  6.02 X 1023 atoms

c.  12.04 X 1023 atoms d.  1.204 X 1024 atoms

Exit Slip 4.  How many molecules of C3OH are in .5 moles?

a.  3.01 X 1023 molecules b.  6.02 X 1023 molecules

c.  9.03 X 1023 molecules d.  1.204 X 1024 atoms

Exit Slip 5.  If there are 1.204 X 1024 particles of gold (Au), how

many moles are there? a.  .5 moles b.  1 mole c.  2 moles

d.  4 moles

Homework   Finish practice questions

12 1 How Many Atoms

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