Turn in last week’s catalyst and grab calculator and worksheet. Sit in lab seats.

Objective: Convert between moles of substances in an equation.Convert between grams of substances in an equation.

Catalyst: (on scratch paper)How many moles are there in the following masses of substances?A. 24.3 g of N2

B. 29.3 g of NaOHC. 12.24 g of Cu(SO4)2

Homework: Complete lab write-up (not full report) Complete C.7 supplement

Group assignments

• Green: 1 g baking soda, 1 mL acetic acid• Blue: 1 g baking soda, 2 mL acetic acid• Yellow: 1 g baking soda, 3 mL acetic acid• White: 1 g baking soda,4 mL acetic acid• Pink: 1 g baking soda, 5 mL acetic acid• Purple 1 g baking soda, 6 mL acetic acid• Goldenrod: 1 g baking soda, 7 mL acetic acid

Some considerations

• NaHCO3 : Baking Soda

• CH3COOH : Acetic Acid– Molarity of acetic acid: .003 mol/mL

• H20: Water– 1 mL of water = 1 gram of water

Modified grading

• Group Grades– 20 points: Pre-Lab & lab

• Individual Grades:– 40 points: Graph and Data Analysis

Grading

• Group Grades– 10 points: Pre-Lab– 30 points: Presentation Data Quality (group)

• Individual Grades:– 15 points: Safe and Productive experimentation– 10 points: Presentation Skills (individual)– 15 points: Peer Grade

Questions to consider:

• What products are being formed? What evidence do you have that these products are being formed?

• Besides water displacement into the graduated cylinder, what other indications do you notice that a chemical reaction is taking place? In which flask is a chemical reaction taking place? How do you know?

• What variables contribute to the amount of water displaced?

• What is the best way to represent your data?

Your Presentation/Paper…• What was your procedure (you may exclude the set-up as it

will be the same for everyone)– Independent, dependent and control variables!

• What were your results– Graph and describe trend

• Analysis– What do you think is happening at the molecular level?– Describe what happens as you increase one variable? Why do

you think this is happening?– Compute the moles of baking soda and vinegar at this point:

What is the molar ratio?– Determine a theoretical weight/volume of your independent

variable that would produce the most gas with the least of the substance.

Information given by chemical equations

2 C6H6 (l) + 15 O2 (g) 12 CO2 (g) + 6 H2O (g)

This equation could be read as 2 moles of benzene reacts with 15 moles of oxygen to produce 12 moles of carbon dioxide and 6 moles of water.

Since the number of molecules in any mole is 6.02 x 1023, a common factor between all species involved in the equation, a MOLE RATIO relationship can be discussed.

Information given by chemical equations

2 C6H6 (l) + 15 O2 (g) 12 CO2 (g) + 6 H2O (g)

The MOLE RATIO for benzene and oxygen is 2 : 15. It can be written as:

2 moles C6H6 or as 15 moles of O2

15 moles O2 2 moles of C6H6

The MOLE RATIO for oxygen and carbon dioxide is 15 : 12. It can be written as:

12 moles CO2 or as 15 moles of O2

15 moles O2 12 moles of CO2

The MOLE RATIO is used for converting moles of one substance into moles of another substance. Without the balanced equation there is no other relationship between two different compounds.

Using the mole ratio to relate the moles of one compound to the moles of another compound is the part of chemistry called

STOICHIOMETRY !!!!!

2 H2 (g) + O2 (g) 2 H2O (g)

Q. How many mole of hydrogen are necessary to react with 2 moles of oxygen in order to produce exactly 4 moles of water?

A. 2 mol O2 (2 moles H2 / 1 mole O2) = 4 mole H2

STOICHIOMETRY

The Stoichiometry Flow Chart

M a s s o f A m ole o f A m o les o f B M a s s o f B

Use Molar mass (A)

Use mole ratio from equation

Use Molar mass (B)

STOICHIOMETRY

2 H2 (g) + O2 (g) 2 H2O (g)

Q1. How many moles of hydrogen are necessary to react with 15.0 g of oxygen?

A. 15.0g O2 (1 mole O2

) ( 2 mole H2) = 0.938 moles H2

32.0 g 1 mole O2

Q2. How many grams of hydrogen are necessary to react with 15.0 g of oxygen?

A. 15.0g O2 (1 mole O2

) ( 2 mole H2) ( 2.016 g H

2) = 1.89 g H2 32.0 g 1 mole O

2 1 mole H2

STOICHIOMETRY

2 H2 (g) + O2 (g) 2 H2O (g)

Q3. How many grams of water are produced from 15.0 g of oxygen?

A. 15.0g O2 (1 mole O2

) ( 2 mole H2

O) ( 18.0 g H2

O) =16.9 g H2O 32.0 g 1 mole O

2 1 mole H2

O

Q4. How much hydrogen and oxygen is needed to produce 25.0 grams of water?

A. 25.0g H2O (1 mole H2

O ) ( 2 mole H2) ( 2.016 g H

2) = 2.80 g H2 18.0 g 2 mole H

2O 1 mole H

2

A. 25.0g H2O (1 mole H2

O ) ( 1 mole O2) ( 32.0 g O

2) = 22.2 g O2 18.0 g 2 mole H

2O 1 mole O

2

Notice that the Law of Conservation of Mass still applies.

How many grams of solid are formed when 10.0 g of lead reacts with excess phosphoric acid?

3. Make a list under the appropriate substance3 Pb+2 H3PO4 Pb3(PO4)2 (s) + 3 H2 (g)

10.0g m=?

Start with what is given:

10.0gPb (1 mole Pb)( 1 mole Pb3

(PO4

)2)(811 g Pb

3(PO

4)2) = 13.1 g Pb3(PO4)2

207 g Pb 3 mole Pb 1 mole Pb3

(PO4

)2

GROUP STUDY PROBLEMS1. How many grams of O2 liquid product can be produced

from 3.55 moles of HgO? 2 HgO 2 Hg + O2

2. How many moles of fluorine are required to produce 3.0 grams of KrF6? Kr + 3 F2 KrF6

3. How many grams of Na2CO3 will be produced from 20.0g of NaHCO3? 2 NaHCO3---> Na2CO3 + H2O + CO2

4. How many grams of O2 are needed to combust 55.0 grams of C2H4? C2H4 + 3O2 -> 2CO2 + 2H2O

5. How many grams of silver is produced when 50.0 g of copper is reacted with excess silver nitrate solution? Cu + 2 AgNO3 Cu(NO3)2 + 2 Ag.

PRACTICE PROBLEMS1. How many grams of gas can be produced from 0.8876 moles of

HgO? 2 HgO 2 Hg + O2

2. How many moles of fluorine are required to produce 12.0 grams of KrF6? Given the equation: Kr + 3 F2 KrF6

3. How many grams of Na2CO3 will be produced from the thermal decomposition of 250.0 g of NaHCO3?

2 NaHCO3---> Na2CO3 + H2O + CO2

5. How many grams of silver is produced when 125.0 g of copper is reacted with excess silver nitrate solution?

Cu + 2 AgNO3 Cu(NO3)2 + 2 Ag.

14.20g

0.182 mol

157.7 g

424.9 g