Specification Learning Outcomes

Question 0

Describe the distribution of mass and charge within an atom

Answer 0

Most of the atom’s mass is concentrated in the nucleus.
The protons provide a positive charge in the nucleus.
The electrons provide a negative charge around the nucleus.

Question 1

Describe protons, neutrons and electrons in terms of relative charge and relative mass.

Answer 1

Relative charge:
Protons +1
Neutrons 0
Electrons -1

Relative mass:
Protons 1
Neutrons 1
Electrons 1/2000

Question 2

Describe the contribution of protons and neutrons to the nucleus of an atom, in terms of atomic number and mass number.

Answer 2

Atomic number- number of protons in the nucleus, identifies the element.
Mass number- the sum of protons and neutrons in the nucleus of an atom.

Question 3

Deduce the number of protons, neutrons and electrons in…
Carbon (12, 6)
X (30, 14, charge 2-)
Y (29, 10, charge 5+)

Answer 3

Carbon:
Protons - 6
Neutrons - 6
Electrons - 6

X:
Protons-14
Neutrons-16
Electrons- 16

Y:
Protons-10
Neutrons-19
Electrons-5

Question 4

Explain the term isotopes

Answer 4

Atoms of an element with different numbers of neutrons and different masses

Question 5

What is C12 used as?

Answer 5

Carbon-12 is used as the standard measurement of relative masses

Question 6

Define the terms relative isotopic mass and relative atomic mass, based on the 12C scale

Answer 6

Relative isotopic mass-
The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12.

Relative atomic mass-
The average mass of an atom of an element on a scale where an atom of carbon-12 is 12.

Question 7

Calculate the relative atomic mass of an element then the relative abundances of its isotopes
E.g. 76% of chlorine atoms are Cl-35, 24% are Cl-37

Answer 7

Relative atomic mass= (R isotopic massits abundance)+(R isotopic massits abundance) divided by 100

Answer=35.5

Question 8

Use the terms relative molecular mass and relative formula mass (you need to be able to use them, not define them)

Answer 8

Relative molecular/formula mass is the average mass of a molecule or formula unit on a scale where an atom of carbon-12 is 12.

(Molecular is used for simple molecules, formula is used for compounds with giant structures

Question 9

Calculate values of relative molecular/formula mass from relative atomic masses.
Mr(CaF2)
Ca=40, F=19

Answer 9

Add up the atomic masses of all the ions in the formula.

Answer=78

Question 10

Explain the term amount of substance

Answer 10

The number of particles measured in moles

Question 11

Explain the term mole (mol)

Answer 11

A mole of substance is the amount of substance that contains the same number of stated elementary units as there are atoms in 12g of Carbon-12.
(Stated elementary units such as atoms, molecules, formula units and ions)

Question 12

Explain the term Avogadro constant (NA)

Answer 12

The number of particles per mole (6.02*10^23 mol^-1h

Question 13

Define and use the term molar mass (gmol^-1)

Answer 13

The mass per mole of a substance

Question 14

Explain the term empirical formula

Answer 14

The simplest whole number ration of atoms of each element present in a compound

Question 15

Explain the term molecular formula

Answer 15

The actual number of each element in a molecule

Question 16

Calculate empirical and molecular formulae, using composition by mass and percentage compositions.

1) 2.4g of Mg combines with 1.6g of O (Mg=24, O=16) what is the empirical formula?
2) CH2 has a relative formula mass of 14 (H=1, C=12) what is the molecular formulae?
3) a compound contains 52.2% C, 13.0% H, 34.8% O. 1 mole of it weighed 46g. (H=1, C=12, O=16) find the molecular formula.

Answer 16

1) MgO
Find the number of moles of atoms, divide by the smallest number (so one of the elements is 1) simplify it until all are whole numbers if possible.
2) C4H8
Find the relative formula mass, how many multiples of it do you need to get to the actual mass? Multiply each element by that number.
3) C2H6O
Find the mass of each element in the compound (e.g. 52.2% of 46…) then find out roughly how many times you need to multiply the relative atomic masses to get to the masses you worked out from percentages.

Question 17

Construct balanced equations for reactions given reactants and products.

1) Zn+2HCl->ZnCl2+H2
2) 2Pb(NO3)2->PbO+NO2+O2
3) NaHCO3+H2SO4->Na2SO4+CO2+H2O

Answer 17

1) Zn+2HCl->ZnCl2+H2
2) 2Pb(NO3)2->2PbO+4NO2+O2
3) 2NaHCO3+H2SO4->Na2SO4+2CO2+2H2O

Question 18

1) What is the mass of 0.2 mol of CaCO3? 1 mol= 100g

2) How many moles is 54g of H2O? 1mol= 18g

Answer 18

Mol=actual mass/mass of one mole (formula mass)

1) 20g
2) 3 mol

Question 19

1) How many moles are there in 6dm^3 of oxygen gas at r.t.p?

2) What volume will be occupied by 88g of propane gas (C3H8) at r.t.p?

Answer 19

Mol=volume dm^3/ 24

1) 0.25 mol
2) 48dm^3

Question 20

Define the terms first ionisation energy and
successive ionisation energy

Answer 20

First ionisation energy:
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Successive ionisation energies:
A measure of the energy required to remove each electron in turn.

Question 21

What are ionisation energies influenced by?

Answer 21

ionisation energies are influenced by nuclear charge- the greater the nuclear charge, the greater the attractive force on the outer electron.

electron shielding- inner electrons repel the outer-shell electrons. This repelling effect is called electron shielding or screening. The more inner shells there are, the larger the shielding effect and the smaller nuclear attraction experienced by the outer electrons.

distance of the outermost electron from the nucleus- the greater the atomic radius, the smaller the nuclear attraction experienced by the outer electrons.