C5.1

Question 1

What is the yield of a product?

Answer 1

It is the mass of a particular product that is formed in a chemical reaction

Question 2

What is the theoretical yield?

Answer 2

The maximum possible mass that could be formed in a reaction, calculated using the given mass of the reactants

Question 3

What do you need to know to calculate the theoretical yield?

Answer 3

The mass of the limiting reactant

The relative formula masses of reactants and products

The balanced equation for the reaction

Question 4

What if the formula for the theoretical yield?

Answer 4

mass of limiting reactant
—————————————— ✖️sum of Mr for products
Sum of Mr for limiting reactant

Question 5

What is the actual yield?

Answer 5

The mass of product that you actually make in a chemical reaction.

Question 6

What is the percentage yield?

Answer 6

the proportion of the theoretical yield that is actually obtained in a reaction

Question 7

How do you calculate the percentage yield

Answer 7

Actual yield
—————————. ✖️100
Theoretical yield

Question 8

Why might the percentage yield be less that 100%

Answer 8

The reactants may react in a different way than expected

The reaction may not go to completion as some of the reactants present do not react

You may lose some of the product when you separate it from the reaction mixture and purify it.

Question 9

What is the atom economy?

Answer 9

It is a measure of how many atoms in the reactants form a desired product

Higher the atom economy, the greater the efficiency

Question 10

How do you calculate atom economy?

Answer 10

Sum of Mr of the desired product
—————————————————— ✖️100
Sum of Mr of all products

Question 11

What is a reaction pathway

Answer 11

A reaction (or series of reactions) chosen for making a particular substance

Question 12

What factors are considered when choosing a reaction pathway

Answer 12

• Yield of the product
• atom economy of the reaction
• usefulness of by-products
• rate of reaction
• equilibrium position

Question 13

What is a by-product ?

Answer 13

A substance formed in the reaction, in addition to the desired product

Question 14

1L = ? dm3

Answer 14

1dm3

Question 15

1ml = ? Cm3

Answer 15

1 Cm3

Question 16

How do you convert Cm3 —> dm3

Answer 16

➗1000

Question 17

How do you convert dm3 —> cm3

Answer 17

✖️1000

Question 18

How do you calculate the concentration in g/dm3

Answer 18

Mass of solute (g) ➗volume of solution (dm3)

Question 19

How do you calculate concentration in mol/dm3

Answer 19

Amount of solute (mol) ➗ volume of solution (dm3)

Question 20

How do you convert mol/dm3 to g/dm3

Answer 20

Multiply the molar mass of the solute to the answer

Question 21

What is a titration

Answer 21

A method in which a neutralisation reaction is used to determine the concentration of an acid or alkali

Question 22

What is a burette

Answer 22

A long graduated glass tube with a tap at the bottom

Question 23

What is the end point of a titration

Answer 23

This is when the alkali is neutralised and the indicator first changes colour.

This is because the two reactants have completely reacted together

Question 24

How does a titration work (generally)

Answer 24

You add a known volume of alkali to a conical flask

Add a few drops of a single indicator

Add acid to the flask from a burette

Question 25

How do you prepare before carrying out a titration

Answer 25

• use a measuring cylinder or a volumetric pipette to measure 25 Cm3 of alkali solution to he conical flask
• the burette has to be clamped vertically so that you obtain accurate readings

When you have filled the burette with acid and added a few drops of indicator to the alkali you are ready

Question 26

What is the titre?

Answer 26

The difference between the final and initial burette reading

Question 27

What is a meniscus

Answer 27

The curve in the surface of a liquid

Question 28

What does repeatable mean

Answer 28

A measure of how close values are to eachother when an experiment is repeated with the same equipment

Question 29

What does accurate mean

Answer 29

A measure of how close a result is to the true value

Question 30

What is precision

Answer 30

A measure of how close the agreement is between the measured values

Question 31

What is a measuring cylinder

Answer 31

A piece of apparatus used to measure different volumes of solution

Question 32

What is a volumetric pipette

Answer 32

A piece of glassware used to measure an accurate volume of solution for a titration

Question 33

How do you carry out a titration?

Answer 33

.

Question 34

What does concordat titres mean

Answer 34

Results from a titration that are within 0.10 Cm3 of each other

Question 35

What do the results from a titration tell you?

Answer 35

• the two reactants used
• the volume and concentration of one of the reactants
• the volume (but not the concentration) of one of the reactants

Question 36

How do you calculate concentration in mol/dm3

Answer 36

Amount (mol) ➗volume (dm3)

Question 37

What is the meaning of molar volume

Answer 37

The volume occupied by one mole of a gas

Question 38

What is the value for molar volume at room temperature and pressure

Answer 38

24 dm3/mol

Question 39

How do you calculate the volume of a substance in the gas state at room temperature and pressure

Answer 39

Volume (dm3) = amount (mol) ✖️ 24 dm3/mol

Question 40

How do you calculate the number of moles of gas if you know the volume

Answer 40

Amount (mol) = volume (dm3) ➗ 24 dm3/mol