E Q's

Question 1

State what is meant by the term electronegativity and hence explain the polarity, if any, of the bonds in chlorine trifluoride, ClF3.

Answer 1

• electronegativity is the (relative) ability of an atom to attract
  the (bonding) electrons (in a covalent bond) (1)
• fluorine is more electronegative than chlorine/fluorine is the
  most electronegative (element) (1)
• so fluorine is δ― and chlorine is δ+

Question 2

What is the test to identify an alcohol?

Answer 2

potassium chloride
misty/white fumes

Question 3

State what is meant by the term molar volume of a gas

Answer 3

volume/space occupied by one mole of a gas at a
specified temperature and pressure/ standard conditions

Question 4

Explain how the student would know if the syringe had a leak in step 2 and what effect this leak would have on the molar mass determined .

Answer 4

• plunger does not return (to zero/original position)
  when released (1)
• molar mass will decrease because ‘air’ has a lower
  molar mass (than 44/carbon dioxide)

Question 5

If the temperature had been less than 20 °C and the pressure remained at one
atmosphere, deduce the effect, if any, on the molar mass calculated.

Answer 5

the calculated molar mass would be greater (1)
- at a lower temperature there would be more
molecules/moles/mass in the same volume
/density is greater.

Question 6

The conditions used in one industrial process are: 420°C and a pressure of 1.7 atm
together with a vanadium(V) oxide catalyst.
It is proposed to change the conditions to 600°C and 10 atm pressure, while still using
the same catalyst.
*(a) Evaluate the feasibility of each of these changes in terms of their effect on the
rate, yield and economics of the reaction.

Answer 6

• increase in temperature will increase rate
• (but) increase in temperature will decrease
  yield/move the equilibrium to the LHS/ produce
  less SO3 because it is an exothermic reaction
  (in the forward direction)
• increase in temperature increases energy
  costs
• increase in pressure has no effect on rate
  (because all the active sites are already
  occupied on a heterogeneous catalyst).
  OR
  increase in pressure will increase rate (of
  reaction)
• increase in pressure will move position of
  eqm to RHS/increase yield because there are
  less moles/molecules (of gas) on the RHS
• but increased pressure increases
  (construction and running) costs/reduces
  economic viability

Question 7

What are the units, if any, of the equilibrium constant, Kc?

Answer 7

dm^3 mol^-1

Question 8

Halogenoalkanes - rate of reaction
Which is the fastest rate - 2-bromobutane, 2-chlorobutane, 2-iodobutane

Answer 8

2-iodobutane is the fastest and 2-chlorobutane is the slowest.
The C-I bond is weaker than the C-CL bond and has a greater polarising effecton the bond, making it more reactive as the bond is weaker. It is the strongest reducing agent which further weaken the bond as the outer electron in 2-iodobutane is easily lost making it more reactive. 2-chlorobutane and 2-idodobutane are both secondary alcohols so the strength of the bond has a greater impact on their reactivity. This is a nucleophilic reaction so the I- acts on the nuclephile in 2-iodobutane. This is why a precipitate of siver halide forms.

Question 9

In the rate of halogenoalkanes reaction, Give a reason for the addition of ethanol to each test tube.

Answer 9

to increase the solubility of / dissolves the
halogenoalkane

Question 10

Write the ionic equation, including state symbols, for the reaction involving
the silver nitrate in the test tube containing chlorobutane

Answer 10

Ag+(aq) + Cl- (aq) produces AgCl(s)