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

mole

Question 3

What does the Avogadro constant represent?

Answer 3

The number of atoms per mole of the

carbon-12 isotope

Question 4

How to calculate the mass of 1 mole of the element?

Answer 4

Mass of 1 mole = relative atomic mass in grams

Question 5

How to calculate moles when mass and molar mass are given?

Answer 5

Moles (mol) = mass (g) / molar mass (g mol -1)

Question 6

State Avogadro’s 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 a gas occupy, at room temperature and pressure?

Answer 7

24 dm3 or 24000 cm3

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

The gas particles are very spread out, hence individual differences has no effect.

Question 10

How to calculate moles when gas volume is given?

Answer 10

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

Question 11

What are the ideal ways in which gases behave? (5)

Answer 11

● In continuous motion
● No intermolecular forces experienced
● Exert pressure when they collide with each other or container
● No kinetic energy is lost in the collisions
● When temperature increases, kinetic energy of gases also
increase

Question 12

Write down the ideal gas equation

Answer 12

pV = nRT
Pressure (Pa) x volume (m3) = number of moles (mol) x gas constant (8.314 J
mol-1)x temperature (K)

Question 13

1 atmospheric pressure is equal to how many pascal?

Answer 13

1 atm = 101325 Pa

Question 14

0℃ is equal to how many

kelvin?

Answer 14

273 K

Question 15

What does concentration of a

solution mean?

Answer 15

It is the amount of solute dissolved in 1 dm3 of solvent

Question 16

How do you calculate moles when concentration and volume are given?

Answer 16

Moles (mol) = concentration (mol dm-3) x volume (dm3)

Question 17

What is a standard solution?

Answer 17

A solution of known concentration

Question 18

Write down the steps to prepare a standard solution

Answer 18

1. Weigh the sample bottle containing solid
2. Transfer sample into beaker and reweigh
3. Record mass difference
4. Add distilled water and stir it with a glass rod until all dissolved
5. Transfer to volumetric flask with washings
6. Make up to 250cm3 mark by adding distilled water
7. Shake flask

Question 19

What does the term

concentrated mean?

Answer 19

Large amount of solute per dm3 of solvent

Question 20

What does the term

dilute mean?

Answer 20

Small amount of solute per dm3 of solvent

Question 21

What is a species in a

chemical reaction?

Answer 21

Any particle that takes part in a reaction

Question 22

What are the four common state symbols?

Answer 22

1. Solid (s)
2. Liquid (l)
3. Gaseous (g)
4. Aqueous (aq)

Question 23

What does the percentage yield mean?

Answer 23

The efficiency of which reactants are converted into products

Question 24

What are the reasons for not obtaining 100% yield? (5)

Answer 24

● Reaction may be at equilibrium
● The reactants may be impure
● Side reactions could happen
● Reactants/products may be left behind while
transferring
● Loss of products during separation and purification

Question 25

How is percentage yield calculated?

Answer 25

actual amount of
product (mol) / theoretical amount of
product (mol) x 100

Question 26

What does atom economy tell us?

Answer 26

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

Question 27

How is atom economy calculated?

Answer 27

Mr of desired product / sum of the Mr’s of all products x 100

Question 28

Does 100% yield mean 100% atom economy?

Answer 28

No, even if all the reactants are

converted into products, not all products of the reaction will be the required products

Question 29

Which type of reaction has 100% atom economy?

Answer 29

Addition reactions (two or more reactants
are combined to form a product)