% Yield, Limiting Reactants and Atom Economy

% yield and atom
economy

Chemistry - Starter questions

1

How do you calculate Mr?

2

What contributes to an atom mass?

3

How do you calculate percentage in terms of x?

4

Describe the plum pudding model of an atom

5

How does reactivity change in Group 1

6

How is the periodic table arranged

KO 3

Chemistry - starter questions

1

Add the mass of all the atoms in the compound

2

Protons and neutrons

3

(x/total) x100

4

A positive ball of mass with impeded negative (electrons) charges

5

The reactivity as you go down group 1

6

It is arranged by atomic number / increase number of protons
(atomic number)

Green pen your answers

% yield and atoms

No atoms are gained or lost in a chemical reaction.
However they may not end up in the compound you
want them to.

CH4 (g) + H2O (g) → 3H2 (g) + CO (g)

Atom economy is the idea of measuring how much
of the starting material ends up as useful products.

Atom economy = Mr of product / Mr of all reactants
x100

% yield and atoms

CH4 + H2O → 3H2 + CO

Mr of CH4 = 16
Mr of H2O = 18

Mr of H2 = 2

% yield and atoms

CH4 + H2O → 3H2 + CO

However there are 3H2 atoms.

2 x 3 = 6

6/34 x100 = 17.647

% yield and atoms

Your turn
% yield and atoms

KO 3

In most reactions there is less product made then
theroised.

This can be for various reasons such as:
- Reaction not going till compilations
- Some of the product may be lost when separated

e.g. filtration.

- Sometimes the an unexpected reaction may

occur.

% yield and atoms

KO 3

% yield and atoms

KO 3

% yield and atoms

Multiple Choice

The ______________ yield is the maximum amount of product possible in a reaction. This determines the amount of product that should be produced in a perfect setting

• Percent
• actual
• stoichiometry
• theoretical

Multiple Choice

Balance the following reaction :
 
CaC₂(s)   +   H₂O(l)   -->   C₂H₂(g)   +   Ca(OH)₂(aq)

• 1,2,2,2
• 1,2,1,1
• 2,1,1,1
• 2,1,2,1

Multiple Choice

Reactant and products might adhere to containers causing actual yield to be less than theoretical yield.

• true

• false

Multiple Choice

Competing reactions might occur forming other products causing your actual yield to be less than your theoretical yield.

• true

• false

Multiple Choice

Some product can be transformed completely into energy causing your actual yield to be less than your theoretical yield.

• true

• false

Multiple Choice

Some product may be lost during filtering causing your actual yield to be less than your theoretical yield.

• true

• false

Multiple Choice

9. Complete the equation for the percent yield of a chemical reaction:
Percent yield=(________)÷(________)×100%

• actual yield; theoretical yield
• theoretical yield; actual yield

Multiple Choice

What is the molar mass of Carbon?

• 6
• 12
• 20
• 40

Multiple Choice

How many moles is 4 grams of Calcium?

• 0.10 moles
• 10 moles
• 44 moles
• 160 moles

Multiple Choice

What is Avogadro's Number?

• 602,000
• 23 x 10⁶
• 10 x 10²³
• 6.02 x 10²³

Multiple Choice

In the image, which reactant is limiting?

• The white molecules, because there are extra.

• The black atoms, because they are completely used up.

• The white molecules, because they are completely used up.

• The black atoms, because there are extra.

Multiple Choice

If a chemist calculates the maximum amount of product that could be obtained in a chemical reaction, he or she is calculating the

• theoretical yield
• mole ratio
• actual yield
• percentage yield

Multiple Choice

7. The amount of product that actually forms when a chemical reaction is carried out in a laboratory is called the _________ yield.

• actual
• theoretical
• percent

Multiple Choice

Theoretical yield = 73g
Actual yield = 62g
Calculate the percent yield.

• 1.16%
• 116%
• 85%
• 76%

Multiple Choice

When reacting Na with Cl₂, we calculated that the theoretical yield should be 13 grams. Our actual yield was 12.5 grams. What is the percent yield?

• 90.4%

• 104%

• 96.15%

• 1.04%

Multiple Choice

Theoretical yield = 73g
Actual yield = 62g
Calculate the percent yield.

• 1.16%
• 116%
• 85%
• 76%

Explanation Slide...

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Fill in the Blank

When 5.00 g of KClO₃ is heated it decomposes according to the equation:

2KClO₃ → 2KCl + 3O₂

Give the % yield to 1 d.p. if 1.78 g of O₂ is produced.

.

Explanation Slide...

​

Fill in the Blank

Magnesium reacts with oxygen as shown in the equation below:

2Mg + O₂ → 2MgO

Calculate the percentage yield of the reaction, given that burning 2.32 g of magnesium produced 2.39 g of magnesium oxide. Give your answer to 1 d.p.

.

Fill in the Blank

Calculate the mass of 2-bromobutane that the student uses (3.s.f)

KO 1

You have 40 minutes to complete SLOP
1.

No questions for the first 5 minutes

2.

Golden silence

3.

Answer all teacher feedback with a green pen

% Yield

Update the DPR