Physical- incorrect questions

Question 1

Give the equation for the third ionisation energy of Mg w state symbols

Answer 1

Mg2+(s)–>Mg3+(g)+e-

Question 2

Explain why the third IE of mg is much higher than the 2nd IE of mg

Answer 2

M1) removing electron from p shell
M2) electron removed has less shielding

Question 3

Explain why CBr4 is not a polar molecule

Answer 3

The C-Br polar bonds cancel out because the molecule is symmetrical.

Question 4

Foul smelling gas

Answer 4

hydrogen sulfide

Question 5

Explain why using a catalyst has no effect on the percentage yield

Answer 5

Affects rate of forward and backward reaction equally

Question 6

Why is Na2CO3 added to unknown substances

Answer 6

Tests to see if it’s acidic/ has H+ ions

Question 7

How can you determine which element a set of ionisation energies belong to?

Answer 7

FInd the largest gap, eg 4th-5th
Count 4 back from group 0, eg Ar-C

Question 8

What is the trend in oxidising ability of group 7 elements going down the period

Answer 8

oxidising ability decreases

Question 9

What is responsible for conducting the electricity in water molecules?

Answer 9

The ions

Question 10

What is responsible for conducting the electricity in metal?

Answer 10

The bonding electrons

Question 11

Suggest one reason other than incomplete combustion or heat transfer to the atmosphere why the student’s value for the enthalpy of combustion of methanol is different from the Data Book.

Answer 11

evaporation of the alcohol (fuel)
experiment not done under standard conditions
heat capacity of copper not taken into account

Question 12

Platinum, palladium and rhodium are metals used inside catalytic converters.
A very thin layer of the metals is used on a honeycomb ceramic support.
Explain why a thin layer is used in this way.

Answer 12

to reduce the amount of metal needed to produce a large surface area

Question 13

Sulfur dioxide (SO2) is produced when some fossil fuels are burned.
How can it be removed?

Answer 13

Sulfur dioxide can be removed from waste gases in a power
station by an acid-base reaction with calcium oxide.

Question 14

Suggest one reason why, other than mean bond enthalpies, why a value for the enthalpy of combustion of a liquid alknae is different from value obtained from calculations of ΔcH

Answer 14

(ALKANE MOLECULES MUST BE GASEOUS IN ORDER TO COMBUST- IT DOESN’T MATTER IF THE FULE ITSELF IS LIQUID OR SOLID IT MUST BE GASEOUS TO UNDERGO COMBUSTION)
M1) the alkane is not gaseous and it would takes energy to convert it to a gas

Question 15

Which of these species is the best reducing agent?+ explain why
Cl2
Cl-
I2
I-

Answer 15

I-
because it already has an extra electron to loose.

Question 16

State which of the elements magnesium and aluminium has the lower
first ionisation energy.
Explain your answer.

Answer 16

Al
(Outer) electron in (3)p sublevel/orbital
Higher in energy/further from the nucleus
so easier to remove

Question 17

student obtained a value for the
enthalpy of reaction of −142 kJ mol−1
A data book value for the enthalpy of reaction is −310 kJ mol−1
Suggest the most likely reason for the large difference between the student’s
experimental value and the data book value.

Answer 17

Heat loss (from the apparatus would mean the experimental value is
smaller/lower/less exothermic than the data source)

Question 18

Ways to imporve required practical 2. Measurement of an Enthalpy Change

Answer 18

• Insulate the beaker or use a polystyrene cup or a
  lid
• To reduce heat loss
• Record the temperature for a suitable time before
  adding the metal
• To establish an accurate initial temperature
• Record temperature values at regular time intervals
• To plot the temperature results against time on a
  graph
• Extrapolate the cooling back to the point of addition
• To establish a (theoretical) maximum temperature
  OR temperature change (e.g. at the 4th minute) OR
  adjust for the cooling /apply a cooling correction

Question 19

What is the best technique to remove the silver chloride that forms when
aqueous solutions of silver nitrate and sodium chloride react?

Answer 19

Filtration

Question 20

How can titration results be lower than the actual value

Answer 20

rinding the burrette with distilled water before filling

Question 21

Which of these has the higehst 1st ionisation energy:
sodium
aluminium
silicone
chlorine

Answer 21

chlorine