Entry Journal 10/311. Calculate the number of grams in 5.6 moles

of Na3PO4.

2. How many L of O2 gas are in 7.5 moles of O2?

Chapter 9Stoichiometry:

The calculation of chemical quantities in chemical

reactions.

Stoic. Survival Kit:• To be successful in this chapter you will need

to:– Balance Chemical Equations– Convert from

• Moles molecules• Moles grams• Moles liters (@ STP)

Stoic. Study Recommendations

• Do the homework the night it is assigned.

• Ask homework questions in class.

• Go back to your homework and fix problems.

• Participate whiteboard exercises

• Practice makes Proficient

Look at Balanced EquationsC5H12(g) + O2(g) CO2(g) + H2O(g)

• Lets look at:– Atoms (just like balancing the equation)– Molecules/formula units– Moles– mass

• The only two that are conserved (same on both sides) are atoms and mass!

1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)

• Most important relationship:

• 1 mole of C5H12(g) reacts with 8 moles of O2(g) to form 5 moles of CO2(g) and 6 moles of H2O(g)

• We used the balanced equations to come up with conversion factors.

Mole-Mole Calculations• Chemical equations provide more

information than we have had before. We can now relate moles of product to moles of reactant in mathematical equations.

1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)

• Mole ratio: A conversion factor derived from the coefficients of a balanced equation.– *** This means that you must ALWAYS check to see if

the equation given is balanced…– Used when you want to relate different chemicals

• Some mole ratios:

1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)

• How this shows up in chemistry:• Example: How many moles of water are

produced when 4 moles of oxygen are reacted?

• Example: How many moles of pentane are needed to produce 12 moles of CO2?

Some Practice:• Al(s) + O2(g)Al2O3(s)

• Write the six mole ratios that can be derived from the equation.

• How many moles of Al are needed to form 3.7 moles of Al2O3?

• ** hint: balance the equation first!!

Al(s) + O2(g)Al2O3(s)

• How many moles of O2 are required to react with 14.8 moles of Al?

• How many moles of Al2O3 are formed with 0.78 mole O2 reacts with Al?

Remember this?

mol

atomsx

1

1002.6 23

The MOLE

Mass (g)Molecules, atoms,

formula units

atomsx

mol231002.6

1massmolar

1mol

mol1

massmolar

Volume (L)

L

mol

4.22

1

mol

L

1

4.22

Remember this? Let’s add more…

mol

atomsx

1

1002.6 23

The MOLE

Mass (g)Molecules, atoms,

formula units

atomsx

mol231002.6

1massmolar

1mol

mol1

massmolar

Volume (L)

L

mol

4.22

1

mol

L

1

4.22

Relate Chemical A toChemical B

xA yB

ymolB

xmolA

Now we can do many more calculations

• Most common calculation: Mass Mass

• It isn’t that much harder, as long as you remember your stuff from chapter 7.

• Hints: – You ALWAYS need to balance the equation.– Use the mole ratio when you need to change

chemicals.

1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)

• How this shows up in chemistry:• Example: How many moles of water are

produced when 20.5 grams of oxygen are reacted?

• Example: How many grams of oxygen gas are needed to react if 2.8 moles of water are formed?

1C5H12(g) + 8O2(g) 5CO2(g) + 6H2O(g)

• Example: How many grams of water will be formed when 552.3 grams of C5H12 are reacted in the presence of oxygen gas?

KClO3 KCl + O2

How many molecules of O2 are produced by the decomposition of 6.54 grams of KClO3?

CO(g) + O2(g) CO2(g)

• How many liters of O2 are required to burn 3.86 liters of CO?

NO2 + H2O NO3 + NO• How many grams of NO2 must react with

water to produce 5.00 x 1023 molecules of NO?

CaC2 + H2O C2H2 + Ca(OH)2

• How many grams of C2H2 are produced by adding water to 5.00 g of CaC2?

• How many moles of CaC2 are needed to react completely with 49 g of water?