1.2 Amount of Substance

Question 1

What is the symbol for amount of substance?

Answer 1

n

Question 2

What is the unit used to measure amount of substance?

Answer 2

Moles

Question 3

What does the Avogadro constant represent?

Answer 3

The number of atoms per mole of carbon-12 isotope

Question 4

How to calculate moles from mass and molar mass?

Answer 4

Moles = mass / molar mass

Question 5

What unit is used for molar mass?

Answer 5

g mol -1

Question 6

State Avogadros law.

Answer 6

Under the same temperature and pressure, one mole of any gas would occupy the same volume

Question 7

How much volume does gas occupy under standard conditions?

Answer 7

24dm3 or 24000cm3

Question 8

Define molar gas volume.

Answer 8

The volume per mole of gas molecules

Question 9

Why do different gas particles occupy the same volume?

Answer 9

Gas particles are spread out, individual differences have no effect

Question 10

How to calculate moles when gas volume is given?

Answer 10

Moles = volume (dm3) / 24
Moles = volume (cm3) / 24000

Question 11

What are the ideal ways in which gases behave? [5]

Answer 11

Continuous motion
No intermolecular forces
Exert pressure when colliding with each other or container
No kinetic energy lost in collisions
When temp increases, kinetic energy increases

Question 12

What is the ideal gas equation?

Answer 12

pV = nRT

Question 13

What does p represent in the ideal gas equation?

Answer 13

Pressure

Question 14

What units does pressure have in the ideal gas equation?

Answer 14

Pa

Question 15

What does V represent in the ideal gas equation?

Answer 15

Volume

Question 16

What unit does volume have in the ideal gas equation?

Answer 16

m3

Question 17

What does n represent in the ideal gas equation?

Answer 17

Number of moles

Question 18

What does R represent in the ideal gas equation?

Answer 18

Gas constant

Question 19

What is the gas constant in the ideal gas equation?

Answer 19

8.314 J mol-1

Question 20

What does T represent in the ideal gas equation?

Answer 20

Temperature

Question 21

What unit does temperature have in the ideal gas equation?

Answer 21

K

Question 22

How many pascal in 1 atmospheric pressure?

Answer 22

1atm = 101325 Pa

Question 23

How do you convert between degrees celcius and kelvin?

Answer 23

Kelvin = degrees celcius - 273

Question 24

What does concentration of solution mean?

Answer 24

The amount of solute dissolved in 1dm3 of solvent

Question 25

How are moles calculated from concentration and volume?

Answer 25

Moles = concentration x volume

Question 26

What is a standard solution?

Answer 26

A solution of known concentration

Question 27

Describe the steps to prepare a standard solution.

Answer 27

1. Weigh the solute using the weigh by difference method 2. DIssolve the solute in a beaker using solvent 3. Pour solution into volumetric flask 4. Rinse beaker using solution and add to flask 5. Add solvent to flask carefully until reaches graduation line 6. Mix solution thoroughly to ensure complete mixing

Question 28

Define concentrated.

Answer 28

Large amount of solute per dm3 of solvent

Question 29

Define dilute.

Answer 29

Small amount of solute per dm3 of solvent

Question 30

What is a species in a chemical reaction?

Answer 30

Any particle that takes part in a reaction

Question 31

What are the four state symbols?

Answer 31

Solid (s) Liquid (l) Gaseous (g) Aqueous (aq)

Question 32

What does percentage yield mean?

Answer 32

The efficiency of which reactants are converted into products

Question 33

What reasons could there be for not obtaining 100% yield? [5]

Answer 33

Reaction may be at equilbrium Reactants may be impure Side reactions may happen Reactants or products may be left behind with transfer Loss of products during separation and purification

Question 34

How is percentage yield calculated?

Answer 34

Percentage yield = (actual amount of product / theoretical amount of product) x 100

Question 35

What is the amount of product measured in the percentage yield equation?

Answer 35

Moles

Question 36

What does the atom economy refer to?

Answer 36

The proportion of desired products compared with all products formed in the reaction

Question 37

How is atom economy calculated?

Answer 37

Atom economy = (molecular mass of desired product / total molecular mass of all products) x 100

Question 38

Does 100% yield mean 100% atom economy?

Answer 38

No Even if all reactants are converted into products, not all products are desired

Question 39

What type of reaction has 100% atom economy?

Answer 39

Addition reactions

Question 40

What is meant by an addition reaction?

Answer 40

Two or more reactants are combined to form a product