rlly ez exam questions

Question 1

give 2 differences between the physical properties of the elements in group 1 and those of transition metals

Answer 1

• lower densities
• are softer

Question 2

in a reaction profile, how does it show when a reaction is exothermic? (1)

Answer 2

level of products is below the level of reactants

Question 3

describe the structure and bonding of diamond (3)

Answer 3

• giant structure
• covalent bonds
• 4 bonds per atom of carbon

Question 4

explain why diamond has a high melting point (3)

Answer 4

• covalent bonds are strong
• many covalent bonds must be broken
• so a lot of energy is required

Question 5

a student adds zinc oxide until its in excess to hydrochloric acid. give one observation that the student could make to show that zinc oxide is in excess (1)

Answer 5

solid remaining

Question 6

rubidium and potassium are added to water, predict one observation you would see that shows that rubidium is more reactive than potassium (1)

Answer 6

rubidium has a brighter flame

Question 7

explain why rubidium is more reactive than potassium (3)

Answer 7

• rubidium atom is larger
• weaker force of attraction between nucleus and outer electron
• so outer electron is more easily lost

Question 8

complete the equation for the reaction of rubidium and water:
Rb + H2O –> ____ + ____
you should balance the equation as well (3)

Answer 8

2 Rb + 2 H2O –> 2 RbOH + H2

Question 9

explain how the alkaline solution of sodium hydroxide is produced when aqueous sodium chloride solution is electrolysed (3)

Answer 9

• sodium ions and hydroxide ions
  are left in solution
• because hydrogen ions are
  discharged
• and because chloride ions are
  discharged

Question 10

Silicon can be extracted by reducing silicon dioxide with different substances.
The equation for one possible reaction is:
2C(s) + SiO2(s) → Si(s) + 2CO(g)
Explain what this reaction shows about the position of silicon in the reactivity series. (2)

Answer 10

• silicon is less reactive than
  carbon
• because carbon displaces
  silicon

Question 11

Aluminium also reduces silicon dioxide.
Carbon is used rather than aluminium to reduce silicon dioxide because carbon is
cheaper than aluminium.
Carbon can be obtained by heating coal.
Aluminium is obtained from aluminium oxide.
Explain why aluminium is more expensive than carbon.
[2 marks]

Answer 11

• more energy is needed to
  obtain aluminium
• because aluminium is obtained by electrolysis

Question 12

Give one reason why the products are difficult to separate if magnesium is used to
reduce silicon dioxide.
[1 mark]

Answer 12

both products are solid

Question 13

Explain why the pH of an acid depends on:
* the strength of the acid
* the concentration of the acid. (4)

Answer 13

• pH depends on H+ ion concentration
• the higher the concentration of H+ ions the lower the pH
• the higher the concentration of an acid the more acid in same volume
• the stronger an acid the greater the ionisation
• so the stronger the acid the lower the pH

Question 14

The student calculated the volume of barium hydroxide solution to be used in the
titration calculation as 23.50 cm3.
Explain why the student used a volume of 23.50 cm3 of barium hydroxide solution in
the titration calculation.
Titration number 1 2 3 4 5
Volume of barium hydroxide
solution used in cm3 23.90 23.45 23.55 23.55 23.45 (4)

Answer 14

• the mean of titration numbers 2
  to 5 values is calculated
• because 23.90 cm3 is an
  anomalous result

Question 15

Mendeleev left spaces marked with an asterisk *
He left these spaces because he thought missing elements belonged there.
Why did Mendeleev’s periodic table become more widely accepted than previous
versions? (3)

Answer 15

• Mendeleev had predicted
  properties of missing elements
• elements were discovered that
  filled the gaps
• properties of these elements
  matched Mendeleev’s
  predictions

Question 16

Sodium is in Group 1 of the modern periodic table.
Describe what you would see when sodium reacts with chlorine (2)

Answer 16

• flame
• white solid forms

Question 17

Explain why carbon nanotubes conduct electricity. (2)

Answer 17

• contain delocalised electrons
• that can move through
  the structure

Question 18

The model of the atom changed as new evidence was discovered.
The plum pudding model suggested that the atom was a ball of positive charge with
electrons embedded in it.
Evidence from the alpha particle scattering experiment led to a change in the model of
the atom from the plum pudding model.
Explain how.
[4 marks]

Answer 18

• most alpha particles passed through the foil
• so the mass of the atom is
  concentrated in the centre
• some alpha particles were reflected
• so the atom has a positively charged centre

Question 19

Give one limitation of using a dot and cross diagram to represent an ammonia
molecule.
[1 mark

Answer 19

only two-dimensional

Question 20

Explain why ammonia has a low boiling point.
You should refer to structure and bonding in your answer.
[3 marks]

Answer 20

• ammonia is a simple molecular structure
• ammonia has weak intermolecular forces
• so little energy is needed to
  overcome the intermolecular
  forces

Question 21

if the overall energy change of a reaction is -1272J exaplin why this reaction is exothermic (2)

Answer 21

• the ovverall enrgy chnage is -1272
• so energy is released to the surroundings

Question 22

Hydrogen fuel cells can be used to power different forms of transport.
Some diesel trains are being converted to run on hydrogen fuel cells.
A newspaper article referred to the converted trains as the new ‘steam trains’.
Suggest why.
[2 marks]

Answer 22

• in a fuel cell hydrogen is
  oxidised
• water is released as steam

Question 23

Aluminium is produced by electrolysing a molten mixture of aluminium oxide and
cryolite.
0 7 . 1 Explain why a mixture is used as the electrolyte instead of using only
aluminium oxide.
(2)

Answer 23

• mixture has a lower melting
  point
• so less energy needed

Question 24

Explain why the positive electrode must be continually replaced.
[3 marks]

Answer 24

the electrode reacts with oxygen
the electrode is carbon /
graphite
(so) carbon dioxide is produced

Question 25

Sodium metal and chlorine gas are produced by the electrolysis of molten sodium
chloride.
0 7 . 6 Explain why sodium chloride solution cannot be used as the electrolyte to produce
sodium metal.
[2 marks]

Answer 25

hydrogen (gas) would be
produced (instead of sodium)
(because) sodium is more
reactive than hydrogen