4.5.2 - Chemical Quantities

Question 1

How are atoms represented?

Answer 1

Symbols in chemical equations

Question 2

What is an element?

Answer 2

A substance made up of one type of atom

Question 3

What is a compound?

Answer 3

A substance formed by the bonding of two or more elements

Question 4

What are the 4 state symbols?

Answer 4

s - Solid
l - Liquid
g - Gas
aq - Aqueous

Question 5

What does (aq) mean?

Answer 5

Aqueous - dissolved substance

Question 6

What happens in a chemical reaction?

Answer 6

Atoms in reactants are rearranged into new products.

Question 7

What is conservation of mass?

Answer 7

The mass of reactants is the same as the mass of the products.

Question 8

How does a balanced equation prove mass is conserved?

Answer 8

There are the same amount of atoms in each element in the reactants and products.

Question 9

Why do some reactions appear to lose mass?

Answer 9

• Open System Reaction
• So the gas in the products escapes

Question 10

Why do some reactions appear to gain mass?

Answer 10

Gas is a reactant

Question 11

What does atomic number tell us about an atom?

Answer 11

How many protons and electrons

Question 12

What does the mass number tell us about an atom?

Answer 12

How many neutrons and protons there are

Question 13

What is Relative Atomic Mass (Ar)?

Answer 13

The mean mass of the atoms and different isotopes in an element.

Question 14

What element are the Relative Atomic Masses (Ar) of all element compared to?

Answer 14

Carbon-12

Question 15

What is the Relative Molecular Mass (Mr)?

Answer 15

Sum of all the Ar’s present

Question 16

Calculate the Mr of CO2.

Answer 16

C = 1 x 12 = 12
O = 2 x 16 = 32

12 + 32 = 44
44

Question 17

What is the relative formula mass of CaCO3?

Answer 17

Ca = 1 x 40 = 40
C = 1 x 12 = 12
O = 3 x 16 = 48

40 + 12 + 48 = 100
100

Question 18

What is the relative formula mass of Na2SO4?

Answer 18

Na = 2 x 23 = 46
S = 1 x 32 = 32
O = 4 x 16 = 64

46 + 32 + 64 = 142
142

Question 19

What is an isotope?

Answer 19

Versions of an element with the same number of protons and electrons but a different number or neutrons

Question 20

How is percentage by mass of an element in a compound calculated?

Answer 20

(Ar of element / Mr) x 100

Question 21

What are chemical amounts measured in?

Answer 21

Moles

Question 22

Define: Mole

Answer 22

The amount of a substance that contains 6.02 x 10^23 atoms / ions / molecules

Question 23

What is the Avogadro constant?

Answer 23

The number of atoms in one mole of a substance

Question 24

What is the value of Avogadro constant?

Answer 24

6.02 x 10^23

Question 25

What is a limiting reactant?

Answer 25

Reactant that is fully used up

Question 26

What does it mean if a reactant is in excess?

Answer 26

There is more than required

Question 27

How is the unknown mass of a substance calculated from known amounts of reactants or products?

Answer 27

The mass will be the same on both sides. Subtract the Mr of the known substances to the find the missing value.

Question 28

What is the equation for calculating the number of moles?

Answer 28

Number of moles = mass / Ar or Mr

Question 29

Define: Solute

Answer 29

The dissolved substance. Aka salt or sugar

Question 30

Define: Solvent

Answer 30

The liquid in which the solute dissolves form a solution. Aka water

Question 31

Define: Solution

Answer 31

A mixture formed by a solute and a solvent.

Question 32

What is a dilute solution?

Answer 32

A solution that does not contain a large number of solute particles.

Question 33

How do you calculate concentraction?

Answer 33

Concentration = mass of solute / volume of solution

Question 34

How many cm^3 in a dm^3?

Answer 34

1000cm^3 = 1dm^3

Question 35

How many litres in a dm^3?

Answer 35

1l = 1dm^3