2019 breadth paper Revision!

Question 1

Which statement about the periodic table is NOT correct?

The elements are arranged in groups with similar chemical properties.

The elements are arranged in periods with repeating trends in properties

The elements are arranged in order of increasing atomic number

The elements in the halogen group increase in reactivity down the group

Answer 1

The elements in the halogen group increase in reactivity down the group.

The reason because is false; They get LESS REACTIVE DOWN THE GROUP because the atoms become larger. The outer shell is further from the nucleus, so electrons are less strongly attracted to it.

Question 2

What molecule contains the LARGEST BOND ANGLE?

C2H4
H2O
NH3
CH4

Answer 2

C2H4
Methene has the largest bond angle because it is trigonal planar therefore having 120 degrees.

Other answers are invalid because:

Water has 2 lone pairs of electrons on the oxygen atom making its shape NON-LINEAR-Bond angle is 104.5 degrees.

Ammonia has a lone pair of electrons on the Nitrogen making its shape Trigonal Pyramidal– Bond angle 107 degrees.

Methane has equal bonded pairs, its shape is Tetrahedral- Bond Angle is 109.5 degrees.

Question 3

What is the percentage composition by mass of nitrogen in (NH4)2CO3?

14. 58%
15. 95%
16. 17%
17. 50%

Answer 3

Answer: Relative atomic mass of Nitrogen is 14
The relative atomic mass of Ammonium carbonate is 96

Then you divide 14 by 96 and multiply it by 100
your answer is 14.58% however since that only accounts for one nitrogen and not two, we multiply the answer by 2 and get 29.17%

The answer is 29.17%

Question 4

Which chemical process is the most sustainable in terms of the atom economy of the organic product?

CO2 + 3H2 —> CH3OH + H2O

CH3CH2OH + NaCl + H2SO4 —> CH3CH2Cl +
NaHSO4 + H2O

CH3CH2Br + NaOH —> CH3CH2OH + NABr

CH3CH2CH2CH2OH —> CH3CH2CH=CH2 + H2O

Answer 4

Method to work out the ‘most sustainable’ atom economy is by:

Working out the reactants / the product and multiply by 100
In this case:
NO. 1 had an atom economy of 64%
NO. 2 had an atom economy of 31.8%
NO. 3 had an atom economy of 30.9%
NO. 4 had an atom economy of 67.6%

The answer is 64% of the last chemical process.

Question 5

8.0 dm^3 of NO is mixed with 6.0 dm^3 of O2 at room temperature and pressure (RTP).
The reaction below takes place until one of the reactants is used up.

2NO(g) + O2(g) —> 2NO2(g)

What is the volume of the mixture at RTP after the reaction has taken place

8. 0dm^3
9. 0dm^3
10. 0dm^3
11. 0dm^3

Answer 5

Method: the ratio between 2NO + O2 is 2:1, therefore, NO is the limiting reactant so you divide 8 by 2 to get 4 and add the O2 with the value 6 to get: 10dm^3.

The answer is: 10dm^3

Question 6

What is the volume of 0.0100mol of N2 at 350 degrees and 200KPa?

A) 145cm^3
B) 259cm^3
c) 145dm^3
d) 259dm^3

Answer 6

Ideal gas equation problem:

Volume= mol x R x T / P where:
R is 8.314 it’s the constant
T is temperature + 273

Volume= 0.0100 x 8.314 x 623 / 200000
Volume = 2.59 x 10^4 m^3 x 10^6
Volume = 258.98cm^3 
Volume = 259cm^3

Question 7

0.24g of an element, X, is reacted with 0.01mol cl2 to form chloride with the formula XCl2.
What is element X?

A) Carbon
B) Magnesium
C) Molybdenum
D) Titanium

Answer 7

Since Cl2 and X have the same ratio it is a simple calculation:

Mass/ mol = Ar 0.24/0.01 =24
24 is similar to 24.3 which is:
Ans: MAGNESIUM

Question 8

which reaction shows chlorine only being oxidised?

Cl2 + H2O —> HCl + HClO
2ClO2 + 2NaOH —> NaClO2 + NaClO3 + H2O
4KClO3 —> 3KClO4 + KCl
MnO2 + 4HCl –> MnCl2 + Cl + 2H2O

Answer 8

In the first equation: Cl is being reduced (gain of electrons)
In the second equation: Cl is still giving electrons to the oxygen so it remains as being oxidised throughout.
In the third equation: Cl is being oxidised already so the answer is invalid
Fourth equation: Cl is getting reduced and it’s oxidised as seen with the stand-alone Cl.

Question 9

(refer to test paper for diagram) Which statement about the reaction is correct?

A) The activation energy of the forward reaction is 120KJ mol-1
B) The activation energy of the reverse reaction is 270 KJ mol-1
C) The enthalpy change of the forward reaction is -30 KJ mol-1
D) The reverse reaction is exothermic

Answer 9

Despite the graph showing you two separate values to put you off, add the two values to work out the ‘activation energy’

You cannot determine the enthalpy change with the values given.

Your activation energy is: 270 KJ mol-1 so look for this value thus the answer is B