Chapter 9 stoich

Chapter 9- Stoichiometry:

• Stoichiometry is like following a recipe

• Focuses on mass or molar relationships

• Key is a balanced equation and reading the equation in terms of…Coefficients

I have a yellow hat on!

The mass relationships between reactants and products in a chemical reaction.

Let’s try this:

1. Type of reaction?

2. Balanced equation

3. How is this read in terms of moles?

4. What are all the possible mole ratios?

5. “RECIPE” for moles to moles, moles to mass, mass to moles and mass to mass

Na + Cl2

Let’s try this:

1. Type of reaction?





Na + Cl2 NaCl

Let’s try this:

1. Type of reaction? Synthesis





Na + Cl2 NaCl

Let’s try this:






2Na + Cl2 2NaCl

Let’s try this:




2 moles of Na react with 1 mole of Cl2 to produce 2 moles of NaCl

2Na + Cl2 2NaCl

Let’s try this:


2 mol Na 2 mol Na 1 mol Cl2 1 mol Cl2 2 mol NaCl 2 mol NaCl

2 mol NaCl 2 Mol NaCl 1 mol Cl2 2 mol Na 1 mol Cl2 2 mol Na

2Na + Cl2 2NaCl

Let’s try this:


Remember that you cannot use a mass-mass

ratio. You must convert to mol first and then

back into grams.

2Na + Cl2 2NaCl

Conversions of Quantities in Moles

CO2 + 2LiOH → Li2CO3 + H2O

How many moles of lithium hydroxide are

required to react with 20 moles of carbon

dioxide, the average amount exhaled by a

person each day?



2 mol LiOH

1 mol CO2



2 mol LiOH x mol LiOH

1 mol CO2 20 mol CO2

X



2 mol LiOH x mol LiOH

1 mol CO2 20 mol CO2

x 40 mol LiOH

X

=

More Practice

Use the following equation to determine how many grams of aluminum must be used to produce 5.00 grams of hydrogen gas?

2 Al(s) + 6 HCl(aq) 2 AlCl3(aq) + 3 H2(g)

Do Now

In the reaction P4 + 5 O2 2 P2O5, how many moles of oxygen are consumed each time 0.500 mol of P2O5 is formed?

Answer: 1.25 mol O2

Limiting ReagentLet’s pretend we have 7,000,000 hot dogs

But only 600 hot dog buns

X 1,000,000

X 100

Limiting ReagentQ- How many hot dogs can you make?

Limiting ReagentQ- How many hot dogs can you make?

A – Only 600

Limiting Reagent Once a reactant is used up, there can be no more products produced

(The substance that is used up first is called the)limiting reagent =

the reactant that limits the amount of the other reactant that can be combined and thus the

product that is produced

Excess reagent = the substance not used up completely

Let’s try a problem:

HCl + NaOH NaCl + H2O

2 mol 2.5 mol

Determine the limiting reagent for this reaction.

(This is done by comparing the 2 given value in

a ratio.)

Let’s try a problem:HCl + NaOH NaCl + H2O

2 mol 2.5 mol

Pick one of the givens and solve:

1 mol HCl x mol HCl

1 mol NaOH 2.5 mol NaOH

x 2.5 mol HCl

=

=

Let’s try a problem:HCl + NaOH NaCl + H2O

2 mol 2.5 mol

2.5 mol HCl: But what does this mean?

This means that in order to react ALL

2.5 mol NaOH, you would need AT LEAST

2.5 mol HCL.

But you only have 2 mol HCl, so it LIMITS

the reaction. Hence: limiting reagent.

Percentage Yield• Theoretical yield = what you calculate or

expect under perfect conditions

• Actual Yield = what you get in the lab

• Percentage Yield = x 100%Actual Yield

Theoretical Yield

Chapter 9 stoich

Spiritual

Transcript of Chapter 9 stoich