Question 18N.3.sl.TZ0.11
| Date | November 2018 | Marks available | [Maximum mark: 9] | Reference code | 18N.3.sl.TZ0.11 |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Compare and contrast, Describe, Explain, Identify, State, Suggest | Question number | 11 | Adapted from | N/A |
Solar energy, which is freely available, is indispensable to life on earth.
Suggest another advantage and one disadvantage of solar energy.
[2]
Advantage:
renewable «energy source»
OR
does not produce greenhouse gases
OR
can be installed «almost» anywhere
OR
low maintenance costs ✔
Disadvantage:
widely dispersed/not concentrated «form of energy»
OR
geography/weather/seasonal dependent
OR
not available at night
OR
energy storage is difficult/expensive
OR
toxic/hazardous materials used in production
OR
concerns about space/aesthetics/local environment where installed
OR
need to be «constantly» cleaned ✔
Accept “can be used for passive/active heating”, “can be converted to electric energy”.
Accept any specific greenhouse gas name or formula for “greenhouse gases”.
Accept “solar cells require large areas”, “solar cell manufacture produces pollution/greenhouse gases”, “higher cost of solar cells «compared with traditional sources such as fossil fuels or hydroelectric»”.
Light can be absorbed by chlorophyll and other pigments.
Consider molecules A and B represented below.
Identify, with a reason, the molecule that absorbs visible light.
[1]
B AND larger/more extensive «electronic» conjugation
OR
B AND «contains» more alternate single and double bonds ✔
Accept more specific statements, such as “sp3 carbon in A prevents conjugation between aromatic rings”.
State a physical property of vegetable oils that makes them very difficult to use as fuel in internal combustion engines.
[1]
high viscosity ✔
Accept “low volatility”, just “viscous/viscosity” OR “does not flow easily”.
Describe how vegetable oils can be converted to a more suitable fuel.
[1]
convert to esters of monoatomic alcohols
OR
react with short-chain alcohols «in the presence of acid or base» ✔
Accept “convert to shorter «carbon chain» esters” OR “transesterification”.
Accept specific alcohols, such as methanol or ethanol.
Contrast the importance of carbon dioxide and methane as greenhouse gases.
[2]
carbon dioxide/CO2 more/most abundant «GHG than methane/CH4»
OR
carbon dioxide/CO2 has «much» longer atmospheric life «than methane/CH4» ✔
methane/CH4 «much» better/more effective at absorbing IR radiation «than carbon dioxide/CO2»
OR
methane/CH4 has a greater greenhouse factor «than carbon dioxide/CO2»
OR
methane/CH4 has a greater global warming potential/GWP «than carbon dioxide/CO2» ✔
Accept “carbon dioxide/CO2 contributes more to global warming «than methane/CH4»”.
Explain, using an equation, the effect of increased carbon dioxide in the atmosphere on the pH of lake water.
[2]
CO2 (g) + H2O (l) H+ (aq) + HCO3– (aq)
OR
CO2 (g) CO2 (aq) AND CO2 (aq) + H2O (l) H+ (aq) + HCO3– (aq) ✔
«increasing [CO2 (g)]» shifts equilibrium/reaction to right AND pH decreases ✔
Accept “H2CO3 (aq)” for “CO2 (aq) + H2O (l)”.
Equilibrium arrows required for M1.
State symbols required for CO2 (g) CO2 (aq) equation only for M1.
Accept “concentration of H+/[H+] increases AND pH decreases” for M2.