Unit 1 Flashcards
(21 cards)
May 2019 The value of molar volume calculated in (b)(iv) was lower than the student expected. Give two reasons for the value being lower than expected. Assume that the correct amounts of hydrochloric acid and magnesium carbonate were used. (2)
- Loss of gas before the bung is inserted / other named reason (MUST HAVE REASON, no marks for just “loss of gas”)
- Some carbon dioxide dissolved in the water
- Temperature of the lab was lower than standard temperature
Spec Explain the changes in first ionisation energy for the elements with atomic numbers from 3 to 10. (4)
- General increase across atomic numbers from 3 to 10 due to increase in nuclear charge
- Electrons are added to the same quantum shells (shielding effect is similar)
- 5 is lower than 4 ⇒ 2p is better shielded than 2s, higher energy. There is only one electron in 2p. Therefore, less energy required to remove one electron in 2p
- 8 is lower than 7 ⇒ repulsion between pairs of electrons in 2p orbitals (easier to remove one)
Spec Explain why the first ionisation energy of element 11 is lower than that of element 3. (3)
- Higher quantum shell
- Further from nucleus ⇒ better shield
Jan 2019 Give a reason why the logarithm of the ionisation energy. Rather than just the ionisation energy. Is used to plot this graph (1)
- The range of numbers / 1402 to 64362 is too large (to fit on a graph / axis), or,
- Logarithms make it easier to plot the numbers
Jan 2019 Explain what can be deduced from the graph about electronic structure of nitrogen (3)
- Jump between ionisation 5 and 6 ⇒ start of new quantum shell (1)
- 2 electrons are harder to remove ⇒ closer to nucleus (1)
- 5 electrons are easier to remove ⇒ further from nucleus (1)
Jan 2019 Explain why the first ionisation energy of oxygen is lower than that of nitrogen (3)
Oxygen: electron is lost from a full 2p orbital
Nitrogen: loses an electron from a half-filled subshell
Repulsion: more repulsion between pair electrons than between electrons in different orbitals so less energy is required to remove the electron in oxygen
Oct 2019 Explain why the first ionisation energy of phosphorus is greater than that of sulphur (2)
Phosphorus
- phosphorus has a half-filled p (sub)shell / one electron in each p orbital / the p orbitals are singly occupied (1)
- more energy is required to remove an unpaired electron (than a paired electron)
OR
Sulfur
- the outermost / 3p electron or the electron being removed in sulfur is paired (1)
or
- less energy is required to remove a paired electron (than an unpaired electron) (must mention PAIRED electrons)
- repulsion between paired electrons (reduces the ionisation energy needed to remove it (1)
Jan 2019 explain why aluminium chloride in solid state has significant covalent character (2)
- An aluminium ion is very small and highly charged (1)
- It polarises / distorts the chloride ion (1)
Or - There is a relatively small difference in electronegativity between aluminium and chlorine (1)
- Electrons are partially shared (1)
Jan 2019 Describe how two AlCl3 molecules are joined together in the dimer. Include a diagram in your answer. (2)
Joined by dative covalent bonds
May 2019 Explain the shape of this molecule using the electron-pair repulsion theory. (3)
- Based on (tetrahedral) arrangement
- (four) regions of bonding electrons / bonding pairs (mention lone pair if any)
- Adopt the positions of minimum repulsion
May 2019 Explain how the malleability of metals depend on their structure and bonding (1)
Ions can slide past each other while still being held together by the electrons (1)
May 2019 Explain two ways in which the physical properties of diamond and graphite differ. Refer to their structure and bonding in your answer. (4)
- Diamond is hard and graphite is soft (1)
- Because diamond has rigid lattice / there is weak forces between layers in graphite (1)
- Graphite conducts electricity and diamond does not (1)
- Because graphite has delocalized electrons (which are free to move) / diamond does not (1)
May 2019 State a use of graphene, identifying the property that makes it suitable for that use. (2)
- Flexible electronics (1)
- As only one atom thick / conducts electricity (1)
Spec Explain the toxicity of carbon monoxide (2)
- Reacts with haemoglobin
- Preventing it from carrying oxygen around the body
May 2019 Used coffee grounds have been suggested as carbon-neutral fuel to replace some fossil fuels. Explain why coffee grounds might be considered a carbon-neutral fuel. (2)
- Carbon dioxide released when the fuel was used / burnt (1)
- Is equal to the carbon dioxide that is absorbed by the plant during photosynthesis (1)
May 2019 Explain how the use of fossil fuels causes climate change (2)
- Fossil fuel releases carbon dioxide that is a greenhouse gas (1)
- Increases greenhouse effect / leads to global warming / causes temperature increase (1)
May 2019 Bananas produce ethene as they ripen. Suggest one advantage and one disadvantage of using ripening bananas as a source of ethene for polymer production. (2)
- Advantage: bananas is a renewable resource, more bananas can be grown (1)
- Disadvantage: bananas only produce a small quantities of ethene / would take a long time / not economically viable / inefficient (1)
May 2019 Burning poly(chloroethene) in an incinerator results in the formation of hydrogen chloride. Suggest how the hydrogen chloride could be removed from the waste gases produced in an incinerator. (1)
- Uses of alkaline scrubbers to form ppt / salt / solid
Or - Injection of powdered activated carbon to the flue
Or - Pass through water / dissolve the HCl in water
Spec Give a reason why a mixture of C3H7Cl molecules is formed (substitution reaction) (1)
- The chlorine free radical can remove a hydrogen from either end carbon atoms or central atoms
- Different C3H7Cl is made
Jan 2019 Give a reason why petrol should not contain high proportion of heptane (1)
- Does not combust efficiently
