LIMITING REACTANTS AND THE AMOUNT OF PRODUCTS FORMED

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Physical Science

OBJECTIVES

After going through this lesson, you are expected to:

1. Determine the limiting reactant/reagent in a chemical reaction,

2. Understand the excess reactant/regent in a chemical reaction, and

3. Calculate the amount of product/s formed in a chemical reaction.;

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Review

____ 1. A catalyst is a substance that can be added to a reaction to increase the reaction rate without getting consumed in the process.

Directions: clap once if the statement is true. Clap twice If the statement is false.

____ 2. Heat is not a catalyst since it can’t be taken out of the reaction in the same amount it was inputted into the reaction.

Directions: clap once if the statement is true. Clap twice If the statement is false.

___ 3. Catalysts increase the rates of chemical reactions by raising the activation energy of the reactions.

Directions: clap once if the statement is true. Clap twice If the statement is false.

____ 4. Collisions only result in a reaction if the particles collide with a certain maximum energy called the activation energy of the reaction.

Directions: clap once if the statement is true. Clap twice If the statement is false.

____5. Decreasing the concentration of reactants increases the collision frequency between reacting particles.

Directions: clap once if the statement is true. Clap twice If the statement is false.

Let me know which

of the following is limiting item :

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Example of Limiting reactant:

How many peanut butter sandwiches could be made from 8 slices bread and 1 jar of peanut butter?

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With 8 slices of bread, only 4 sandwiches could be made. The bread is the limiting item.

Four table settings can be made.

What is the limiting item?

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The limiting item is the spoon.

In a table setting, there is 1�plate, 1 fork, 1 knife, and�1 spoon. �

If a carpenter had two tabletops and seven table legs, how many table/ tables he could build?

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He could only build one four-legged table. The number of table legs is the limiting factor.

Pre- test

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Identify the key term referred in each statement. Write your answer on a separate sheet of paper. Choose your answer from the words above

______1. Substances originally present in a chemical reaction that are used to produce products after the reaction.

______2. Substance produced in the chemical reaction.

_______3. A written chemical symbol to represent the process of chemical reaction.

_______4. In a chemical reaction, it limits the amount of substance that may be produced.

________5. A reactant which is not used up after the chemical reaction is done.

Product Limiting reactant Reactant Chemical equation

Excess reactant

Pre- test Part II

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6. It is the reactant that produces a lesser amount of product.

1. Excess Reactant b. Percent Yield

c. Limiting Reactant d. Co-Factor

7. What is the calculation of the relationship of reactant and product in chemical equation.

a. Molality b. Stoichiometry

c. Balancing Equation d. Percent Yield

8. It is the maximum amount of product you would expect from a reaction based on the amount of limiting reagent

1. Theoretical yield b. Limiting Reactant

c. Excess Reactant d. Product Difference

Pre- test

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9. . They are the reactants that are not used up when the reaction is finished.

1. Excess Reagents b. Solute

c. Limiting Reagents d. Solution

10. It deals with the process that involves rearrangement of the molecular or ionic structure of a substance to form a new substance or product.

a. Chemical Equilibrium b. Chemical Reaction

c. Chemical Symbols d. Stoichiometry

KEY TERMS:

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Stoichiometry

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is a branch of chemistry that establishes mole and mass relationships between reactants and/or products in a chemical reaction to determine desired quantitative data.

LIMITING REACTANT

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A limiting reactant in a chemical reaction is the substance that

-Is used up first.

-Stops the reaction.

-Limits the amount of product that can form.

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A substance's molar mass is calculated by multiplying its relative atomic mass by the molar mass constant (1g/mol).

The molar mass constant can be used to convert mass to moles.

By multiplying a given mass by the molar mass, the amount of moles of the substance can be calculated.

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CHEMICAL REACTION

CHEMICAL BALANCING

CHEMICAL BALANCING

CHEMICAL BALANCING

CHEMICAL BALANCING

QUIZ TIME

COPY AND ANSWER

SHOW YOUR SOLUTION ON A

1 WHOLE SHEET OF PAPER

Balancing Chemical Equations

(1) __ Na₃PO₄ + __ HCl → __ NaCl + __ H₃PO₄

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(2) __ TiCl₄ + __ H₂O → __ TiO₂ + __ HCl

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(3) __ C₂H₆O + __ O₂ → __ CO₂ + __ H₂O

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(4) __ FeS + __ O₂ → __ Fe₂O₃ + __ SO₂

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(5) __ CaCl₂ + __ Na₃PO₄ → __ Ca₃(PO₄)₂ + __ NaCl

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ARE YOU’VE DONE!!!

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1. Na₃PO₄ +3 HCl → 3 NaCl + H₃PO₄
2. TiCl₄ + 2 H₂O → TiO₂ + 4 HCl
3. C₂H₆O + 3 O₂ → 2 CO₂ + 3 H₂O
4. 4 FeS + 7 O₂ → 2 Fe₂O₃ + 4 SO₂
5. 3 CaCl₂ + 2 Na₃PO₄ → Ca₃(PO₄)₂ + 6 NaCl

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WHAT IS LIMITING REACTANT?

EXAMPLE PROBLEM #1:

STEP 1: WRITE THE BALANCED CHEMICAL EQUATION

FOR THE REACTION DESCRIBE IN THE PROBLEM.

WHAT IS LIMITING REACTANT?

STEP 2: CALCULATE THE MOLAR MASS OF THE REACTANTS.

WHAT IS LIMITING REACTANT?

STEP 3: Divide the calculated molar mass of the given element or compound from the given mass(given in problem).

WHAT IS LIMITING REACTANT?

STEP 4: Then, the number of moles are divided by the coefficient indicated in the balanced chemical equation.

For Al: 0.167 mol of Al X 1 mol of AlCl3

1 mol of Al

= 0.167 mol of AlCl3

For NaCl: 0.039 mol of NaCl X 1 mol of AlCl3

3 mol of NaCl

= 0.013 mol of AlCl3

WHAT IS LIMITING REACTANT?

WHAT IS LIMITING REACTANT?

STEP 5: Find the grams of AlCl3 formed.

We can use the moles of limiting reagent plus the stoichiometric ratios from our balanced reaction to calculate the theoretical yield.

Theoretical Yield = 0.013 mol of AlCl3 x 133.33g of AlCl3

1 mol of AlCl3

= 1.73 g of AlCl3

The theoretical yield is usually expected to have units of mass, so we can convert moles of AlCl3 to grams using the molecular weight:

Atomic mass Al - 26.98

Atomic mass Cl - 3x 35.45 = 106.35

106.35 + 26.98 = 133.33g

WHAT IS LIMITING REACTANT?

1. The Limiting reactant- Sodium Chloride (NaCl)
2. The excess reactant – Aluminum (Al)
3. 1.73g of AlCl3 formed

WHAT IS LIMITING REACTANT?

EXAMPLE PROBLEM #2:

If a reaction vessel contains 0.15 mol of KO2 and 0.10 mol of H2O, what is the limiting reactant? How many moles of oxygen can be produced?

KO₂ + H₂0 KOH + O₂

STEP 1: WRITE THE BALANCED CHEMICAL EQUATION FOR THE REACTION DESCRIBE IN THE PROBLEM.

WHAT IS LIMITING REACTANT REACTANT?

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4KO₂ + 2H₂0 4KOH + 3O₂

STEP 2: The number of moles indicated in the given problem times the number of mol of the element or compound being asked in the problem divided by the coefficient indicated in the balanced chemical equation.

For KO2: 0.15 mol of KO₂ x 3 mol of O₂

4 mol of KO₂

= 0.113 mol of O₂

For H₂0: 0.10 mol of H₂O x 3 mol of O₂

2 mol of H₂O

= 0.15 mol of O₂

WHAT IS LIMITING REACTANT?

0.15 mol of KO2 and 0.10 mol of H2O

4KO2 + 2H20 4KOH + 3O2

The Limiting Reactant – KO₂

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Amount of O₂ formed – 0.113 mol

WHAT IS LIMITING REACTANT?

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Note: The amount of product that can be formed based on the limiting reactant is called the THEORETICAL YIELD.

LET'S EXERCISE

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2.80 g

26.98 g/mol

=

0. 1037 mol

Cl =

4.25 g

35. 45g/mol

= 0.1199 mol

R1

R2

Al =

LET'S EXERCISE

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0. 1037 mol of Al X

Cl =

2 mol AlCl3

3 mol Cl2

0.1199 mol Cl X

R1

R2

Al =

2 mol Al

2 mol AlCl3

=

0. 1037 mol of AlCl3

= 0. 0799 mol of AlCl3

The limiting reactant is Al.

Cl is the excess reactant

(0.1199 mol)

LET'S EXERCISE

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2C + O2 (g) 2 CO2 (s)

3.20 g

12. 01g/mol

=

0. 266 mol

1.25 g

32.00 g/mol

O2=

= 0.039 mol

R1

R2

C=

LET'S EXERCISE

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2C + O2 (g) 2 CO2 (s)

2 mol CO2

2 mol C

=

0. 266 mol C

1 mol O2

O2=

0.039 mol O2

R1

R2

C=

X

0.266 mol of CO2

X

2 mol CO2

=0.078 mol of CO2

The limiting reactant is Oxygen gas (O2). (0.039 mol)

Carbon (C) is the excess reactant - (0.266 mol)

LET'S EXERCISE

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4NH3 (g) + 5 O2 4NO(g) + 6H2O(g)

2.00g NH3 X

1 mol NH3

17.0 g NH3

X

4 mol NO

4 mol NH3

X

30.0 g NO

1 mol NO

=

3.53 g NO

R1

R2

LET'S EXERCISE

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4NH3 (g) + 5 O2 4NO(g) + 6H2O(g)

4.00g O2 X

1 mol O2

32.0 g O2

X

4 mol NO

5 mol O2

X

30.0 g NO

1 mol NO

=

3.00 g NO

The limiting reactant is O2 (oxygen gas)

Post- test

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Limiting Reactant And The Amount Of Product Form

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BF3 (g) + H2 (g) B + HF

1. If 0.10 mol of BF3 is reacted with 0.25 mol H2, which is the limiting reactant.
2. What is the maximum amount of HF (in grams) that can be produced from these amounts?

Limiting Reactant And The Amount Of Product Form

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CuCl2 + NaNO3 (NO3)2+ NaCl

3. The reaction for the combustion of Ethane is shown by the balanced reaction below.

C2H6 + O2 H2O + CO2

1.45g C2H6 was burned in the presence of 4. 50g O2. Determine the limiting reactant.

THANK YOU!

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