AS/A2 mixed questions

Question 1

Which bonds or interactions are responsible for the higher boiling point of hydrogen iodide

Answer 1

Induced dipole dipole interactions

Question 2

Describe a method to obtain a pure dry sample of alkene from alcohol

Answer 2

Use separating funnel , separate organic and aqueous layer
dry with anhydrous salt e.g. MgSO4
Redistill

Question 3

What are bond angles for
C-H
O-H
COOH

Answer 3

C-H = 109.5
O-H = 104.5
COOH = 120

Question 4

How could the student measure the pH continuously as the NaOh is added

Answer 4

Use a pH meter

Question 5

Suggest why I2 is not very soluble in water

Answer 5

I2 is non polar
it does not form H bonds with water

Question 6

What type of reaction has the greatest atom economy

Answer 6

Addition

Question 7

Explain why the boiling point of PH3 is lower than the boiling point of NH3

Answer 7

NH3 has hydrogen bonding and PH3 does not have hydrogen bonding
Hydrogen bonding is stronger and requires more energy to overcome the bond

Question 8

Explain why the boiling point of PH3 is lower than the boiling point of AsH3

Answer 8

AsH3 has more electrons than PH3
Therefore has stronger London Forces and more energy is required to overcome the bond

Question 9

Explain why a CF4 molecule has polar bonds but does not have an overall dipole

Answer 9

It has polar bonds because F is more electronegative than C atom
It has no overall dipole as the dipoles cancel and is a symmetrical shape

Question 10

what is bond angle for COOH

Answer 10

120 - TRIGONAL planar

Question 11

what give the numerical value of the Avogadro constant

Answer 11

The number of electrons lost by 20.05g of calcium when it reacts with oxygen

Question 12

Explain what is meant by the term weighted mean mass

Answer 12

The mean mass taking into account the relative abundancies of the
isotopes

Question 13

A closed system is required for dynamic equilibrium to be established.

State one other feature of this dynamic equilibrium.

Answer 13

The rate of the forward reaction equals rate of the backward reaction

Question 14

What conditions are needed for the reaction to form bleach

Answer 14

cold AND dilute (sodium hydroxide)

Question 15

State how and explain why the attraction between nuclei and outermost electrons in gaseous atoms varies across Period 3.

Answer 15

Attraction between nuclei and electron increases as nuclear charge increases

Question 16

What is meant by the term average bond enthalpy?

Answer 16

when one mole of bonds is broken

Question 17

State le Chatelier’s principle.

Answer 17

The (position of a dynamic) equilibrium shifts to minimise (the effect of) any change

Question 18

State two ways that the use of catalysts helps chemical companies to make their processes more sustainable and less harmful to the environment.

Answer 18

lower temperatures

Less (fossil) fuels burnt

Question 19

The graph shows that rate of reaction decreases over time.

Explain why, in terms of collision theory.

Answer 19

Less acid concentration
so less frequent collisions

Question 20

In the experiment the water in the beaker was heated for 5 minutes. The student thought that the experiment could be improved by heating the water for 10 minutes.

Explain whether the accuracy in the student’s calculated value for Δc H may or may not be improved by heating for longer.

Answer 20

Less accurate due to greater heat losses

More accurate due to smaller % uncertainty in temperature change

Question 21

Explain why organic product is formed in a much greater quantity than the other organic product (major/minor)

Answer 21

Major product forms from most stable carbocation
Carbocation bonded to fewer H bonds

Question 22

An organic liquid is contaminated with acid. The liquid is placed in a separating funnel.
What is the correct sequence for the operations that follow

Answer 22

Neutralise
Wash
Separate organic layer
Dry
Distil