rlly ez exam questions Flashcards
give 2 differences between the physical properties of the elements in group 1 and those of transition metals
- lower densities
- are softer
in a reaction profile, how does it show when a reaction is exothermic? (1)
level of products is below the level of reactants
describe the structure and bonding of diamond (3)
- giant structure
- covalent bonds
- 4 bonds per atom of carbon
explain why diamond has a high melting point (3)
- covalent bonds are strong
- many covalent bonds must be broken
- so a lot of energy is required
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)
solid remaining
rubidium and potassium are added to water, predict one observation you would see that shows that rubidium is more reactive than potassium (1)
rubidium has a brighter flame
explain why rubidium is more reactive than potassium (3)
- rubidium atom is larger
- weaker force of attraction between nucleus and outer electron
- so outer electron is more easily lost
complete the equation for the reaction of rubidium and water:
Rb + H2O –> ____ + ____
you should balance the equation as well (3)
2 Rb + 2 H2O –> 2 RbOH + H2
explain how the alkaline solution of sodium hydroxide is produced when aqueous sodium chloride solution is electrolysed (3)
- sodium ions and hydroxide ions
are left in solution - because hydrogen ions are
discharged - and because chloride ions are
discharged
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)
- silicon is less reactive than
carbon - because carbon displaces
silicon
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]
- more energy is needed to
obtain aluminium - because aluminium is obtained by electrolysis
Give one reason why the products are difficult to separate if magnesium is used to
reduce silicon dioxide.
[1 mark]
both products are solid
Explain why the pH of an acid depends on:
* the strength of the acid
* the concentration of the acid. (4)
- 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
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)
- the mean of titration numbers 2
to 5 values is calculated - because 23.90 cm3 is an
anomalous result
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)
- Mendeleev had predicted
properties of missing elements - elements were discovered that
filled the gaps - properties of these elements
matched Mendeleev’s
predictions
Sodium is in Group 1 of the modern periodic table.
Describe what you would see when sodium reacts with chlorine (2)
- flame
- white solid forms
Explain why carbon nanotubes conduct electricity. (2)
- contain delocalised electrons
- that can move through
the structure
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]
- 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
Give one limitation of using a dot and cross diagram to represent an ammonia
molecule.
[1 mark
only two-dimensional
Explain why ammonia has a low boiling point.
You should refer to structure and bonding in your answer.
[3 marks]
- ammonia is a simple molecular structure
- ammonia has weak intermolecular forces
- so little energy is needed to
overcome the intermolecular
forces
if the overall energy change of a reaction is -1272J exaplin why this reaction is exothermic (2)
- the ovverall enrgy chnage is -1272
- so energy is released to the surroundings
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]
- in a fuel cell hydrogen is
oxidised - water is released as steam
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)
- mixture has a lower melting
point - so less energy needed
Explain why the positive electrode must be continually replaced.
[3 marks]
the electrode reacts with oxygen
the electrode is carbon /
graphite
(so) carbon dioxide is produced
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]
hydrogen (gas) would be
produced (instead of sodium)
(because) sodium is more
reactive than hydrogen
