Chemistry Bridging Course

Question 1

Atomic Number

Answer 1

Number of protons in the nucleus

Question 2

Mass Number

Answer 2

The total number of protons and neutrons in the nucleus

Question 3

Cation

Answer 3

Positive ion which has less electrons than protons

Question 4

Anion

Answer 4

Negative ion which has more electrons than protons

Question 5

Isotopes

Answer 5

Atoms of the same element with the same number of protons but different number of neutrons

Question 6

Do isotopes of the same element have the same chemical properties

Answer 6

Yes, they have the same electron configuration (same number of electrons)

Question 7

What physical properties of isotopes of the same element might be different ?

Answer 7

The mass, density, boiling point, diffusion rate

Question 8

Relative Atomic Mass , Ar

Answer 8

The weighted mean mass of an atom compared with 1/12th mass of an atom of carbon-12

Question 9

Relative Isotopic Mass

Answer 9

The mass of an isotope compared with 1/12th mass of an atom of carbon-12

Question 10

Ar Value

Answer 10

Mass of an element (mass number)

Question 11

Relative Formula Mass (Mr)

Answer 11

Mass of each atom multiples by how many of each atom there is
Ar values of each atom
e.g O2 (oxygen) = 16 x 2
Mr = 32

Question 12

Water of crystallisation

Answer 12

eg CuSO4.5H20
The full stop is the water of crystallisation
You multiply the Mr of water (1+1+16=18) by the number in front of H2O in this case 5
so 18x5

Question 13

Diatomic Substances

Answer 13

O2 Oxygen
H2 Hydrogen
N2 Nitrogen
F2 Fluorine
Br2 Bromine
I2 Iodine
Cl2 Chlorine

Question 14

Polyatomic Substances

Answer 14

H2O Water - Molecule
NaOH Sodium Hydroxide - Lattice

Question 15

Molecular Formula

Answer 15

Actual number of atoms in each element in a molecule
e.g Glucose = C6H12O6
6 Carbons
12 Hydrogens
6 Oxygen

Question 16

Empirical Formula

Answer 16

Simplest whole number ratio of atoms of each element in a compound
e.g Glucose = C6H12O6 = CH2O

Question 17

Calculating Empirical Formula

Answer 17

Step 1: Mass or Percentage/Ar for each element
Step 2: Divide all the answers by the smallest answer from step 1
Step 3: Find the simplest whole number ratio
1.49 or 1.5 can’t be rounded up to 2.
Multiply all rations till they are whole numbers

Question 18

Calculating The Molecular Formula From The Empirical Formula (with Mr known)

Answer 18

Step 1: Calculate Empirical Formula

Step 2: Work out empirical mass e.g CH2 = 12+2 = 14

Step 3: Divide Mr by empirical mass which is the multiple e.g 56/14 = 4

Step 4: Multiple empirical formula by the multiple = CH2 x 4 = C4H8

Question 19

Calculating The ‘Water of Crystallisation’
Example 1

Answer 19

CuSO4.xH2O
x = water of crystallisation
CuSO4.5H2O
5H2O = water of crystallisation
. = 18 x number in front if H2O
Step 1: Calculate the mass of the anhydrous salt (mass of crucible&resiude - mass of crucible)
Step 2: Calculate the mass of water lost
(mass of crucible&hydrated salt - mass of crucible&residue)
Step 3: Ratio of Anhydrous (without water) salt : water
Use empirical formula
Step 4: Find the simplest whole number ratio of anhydrous salt : water
Step 5: The number for water is the number that goes in front of H2O

Question 20

Calculating the ‘Water of Crystallisation’
Example 2

Answer 20

Step 1: Calculate the mass of water lost:
(Mass of hydrated salt - mass of anhydrous salt) which equals the mass of water
Step 2: Ratio of anhydrous salt : water using empirical formula
Step 3: Find the simplest whole number ratio

Question 21

Endings

Answer 21

‘ide’ - element negative ion (anion) with a negative charge
‘ate’ - compound negative ion (anion) with oxygen

Question 22

Polyatomic Ions

Answer 22

Ammonium- NH4(+)
Hydroxide- OH(-)
Nitrate (v) NO3(-)
Carbonate - CO3(2-)
Sulfate (VI) - SO4(2-)
Phosphate - PO4(3-)

Question 23

Combustion of Fuels

Answer 23

Burning - Reacting with Oxygen
Balance those equations in alphabetical order
1-Carbon 2-Hydrogen 3-Oxygen