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Stoichiometry – Limiting & Excess Reagents

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Limiting Reagent =

Ex:

Excess Reagent =

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How many bikes can you make from the following supplies?

-

Limiting Reagent

=

Excess Reagent

=

-

-

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Calculating Limiting Reagents

1)

-

2)

- NEED > HAVE =

Ex:

- NEED < HAVE =

Ex:

3)

4)

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Ex: 2 Na + Cl2 2 NaCl

A) Limiting reagent?

B) Amount of NaCl produced? (58.44 g/mol)

C) Amount of excess reagent left over?

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

6 of 20

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

-

= -

-

-

-

= -

-

-

-

-

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

7 of 20

A) Limiting reagent?

-

-

-

= -

-

-

-

= -

-

-

-

-

=

-

&

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

8 of 20

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

A) Limiting reagent?

=

-

-

-

-

= -

-

-

&

Excess reagent

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

9 of 20

-

-

B) Amount of NaCl produced?

-

= -

-

Entered in BCA Table

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

10 of 20

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

A) Limiting reagent?

= -

-

-

-

-

= -

-

-!!!

&

Excess reagent

-

-

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

11 of 20

-

-

B) Amount of NaCl produced?

-

= -

-

-

=

*Always Start with Limiting Reagent!!!*

Entered in BCA Table

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

12 of 20

C) Amount of excess reagent left over?

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

= -

Ex: 2 Na + Cl2 2 NaCl

154.1 g of sodium (22.99 g/mol) reacts with 227.2 g of chlorine (70.90 g/mol):

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A) Limiting reagent?

B) Amount of Cu2S produced? (159.17 g/mol)

C) Amount of excess reagent left over?

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

Ex: 2 Cu + S Cu2S

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

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-

-

-

= -

-

-

-

= -

-

-

Ex: 2 Cu + S Cu2S

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

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A) Limiting reagent?

-

-

-

= -

-

-

-

= -

-

-

-

-

=

-

&

Ex: 2 Cu + S Cu2S

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

16 of 20

A) Limiting reagent?

=

=-

-

-!!!

&

Excess reagent

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

2 Cu

S

Cu2S

-

-

-

-

-

-

-

Ex: 2 Cu + S Cu2S

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

17 of 20

-

-

B) Amount of Cu2S produced?

-

= -

-

Entered in BCA Table

Ex: 2 Cu + S Cu2S

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

18 of 20

A) Limiting reagent?

=

=-

-

-!!!

&

Excess reagent

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

2 Cu

S

Cu2S

0 mols

1.26 mols

.780 mols

- 1.26 mols

0 mols

- .630 mols

.150 mols

Ex: 2 Cu + S Cu2S

-

-

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

19 of 20

-

-

B) Amount of Cu2S produced?

-

= -

*Always Start with Limiting Reagent!!!*

Entered in BCA Table

Ex: 2 Cu + S Cu2S

-

-

=

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):

20 of 20

C) Amount of excess reagent left over?

-

-

-

=

Ex: 2 Cu + S Cu2S

 

 

Reactant

Reactant

Reactant

🡪

Product

Product

Product

Reaction Equation

 

 

 

 

 

 

 

Before

 

 

 

 

 

 

 

Change

 

 

 

 

 

 

 

After

 

 

 

 

 

 

 

-

-

-

-

-

-

-

-

-

-

-

-

80.0 g of copper (63.55 g/mol) reacts with 25.0 g of sulfur (32.07 g/mol):