12 9 How Many Grams

Launch: 12/9   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 from grams to grams using molar mass and mole ratios as conversion factors

Tonight’s HW: Finish practice problems

Launch 12/9 3.  Which of the following is a mole ratio for the

equation, 2C3H8 + 7O2 6CO2 + 8H2O

a. 

b. 

c. 

d. 

2 mol C3H8 1 mol O2 7 mol O2

5 mol CO2 7 mol O2

2 mol C3H8 7 mol O

8 mol H2O

Launch 12/9 __Na + __H2O __NaOH + __H2

5.  When the above equation is completely balanced, the coefficient for NaOH would be

a.  1.

b.  2. c.  4.

d.  8.

Announcements   Practice unit exam on Friday

  Worth a quiz grade

  A blank on you grade printout means it is missing!   Make-up work must be in by Wednesday of next week

  Binder check!

  Unit exam on Thursday of next week (12/17)

How many grams? Mr. Heffner 12/9/09

The “Heart Of Chemistry”

Moles Grams Atoms

? grams 1 mole

1 mole ? grams

6.02 X 1023 atoms 1 mole

1 mole 6.02 X 1023 atoms

The “Heart of Chemistry”

Moles Grams

? grams 1 mole

1 mole ? grams

? moles ? moles

Special path for gram gram conversions

Mole Ratio

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

1.  Write down the starting information and look at the ending information.

2.  Using the “Heart of Chemistry”, pick the correct conversion factor(s).

3.  Cancel like terms and do the math!

number “How many…”

Example #1 2H2 + O2 2H2O

In the equation above, how many grams of O2 are required to completely react with 4.04 grams of H2?

  Step #1: Write down the starting information and look at the ending information.

4.04g H2

2H2 + O2 2H2O

In the equation above, how many grams of O2 are required to completely react with 4.04 grams of H2?

  Step #2: Pick the correct conversion factor(s).

1 mol H2 2.02g H2

Example #1

4.04g H2 X =1 mol O2 2 mol H2

X32.00g O2 1 mol O2

X

2H2 + O2 2H2O

In the equation above, how many grams of O2 are required to completely react with 4.04 grams of H2?

  Step #3: Cancel like terms and do the math!

1 mol H2 2.02g H2

Example #1

4.04g H2 X =1 mol O2 2 mol H2

X32.00g O2 1 mol O2

X

=4.04 X 1 X 1 X 32.00 g O2 2.02 X 2 X 1

=4.04 X 32.00 g O2 4.04

32.00 g O2 =

Example #2 Na + 2H2O 2NaOH + H2

If 54.06 grams of water (H2O) are mixed with excess sodium, then how many grams of hydrogen gas (H2) are produced?

  Step #1: Write down the starting information and look at the ending information.

54.06g H2O

Na + 2H2O 2NaOH + H2

If 54.06 grams of water (H2O) are mixed with excess sodium, then how many grams of hydrogen gas (H2) are produced?

  Step #2: Pick the correct conversion factor(s).

1 mol H2O 18.02g H2O

Example #2

54.06g H2O X =1 mol H2 2 mol H2O

X2.02g H2 1 mol H2

X

Na + 2H2O 2NaOH + H2

If 54.06 grams of water (H2O) are mixed with excess sodium, then how many grams of hydrogen gas (H2) are produced?

  Step #3: Cancel like terms and do the math!

1 mol H2O 18.02g H2O

Example #2

54.06g H2O X =1 mol H2 2 mol H2O

X2.02g H2 1 mol H2

X

=54.06 X 1 X 1 X 2.02g H2 18.02 X 2 X 1

=54.06 g H2 18.02

~3g H2 =Round it!

Round it!

Whiteboards   Work in pairs

  Trade-off marker every question

  Partner without the marker should be checking work at each step!

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

  Lift board only when prompted

How many grams of H2O would be produced from reacting 64.00g of O2?

2H2 + O2 2H2O

How many grams of O2 would be required to completely

react with 6.06g of H2?

2H2 + O2 2H2O

If 64.00 grams of O2 are reacted, how many grams of

water (H2O) are produced?

2H2 + O2 2H2O

If 1.01 grams of H2 are reacted, how many grams of

water (H2O) are produced?

2H2 + O2 2H2O

Practice Questions   Practice questions worksheet

Homework   Finish practice questions worksheet