| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.sl.TZ0.10 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Calculate | Question number | 10 | Adapted from | N/A |
Question
Glucose, C6H12O6, is a monosaccharide that our body can use as a source of energy.
Deduce the equation for the cellular respiration of glucose.
Calculate the energy, in kJ, produced from 15.0g of glucose if its enthalpy of combustion is −2803kJmol−1.
Glucose is the basic building block of starch which can be used to make bioplastics. Outline two advantages and two disadvantages of biodegradable plastics.
Two advantages:
Two disadvantages:
Bioplastics are broken down by enzyme catalysed reactions. Sketch a graph illustrating how the rate of this reaction varies with pH.
Markscheme
C6H12O6 (aq) + 6O2 (aq) → 6CO2 (aq) + 6H2O (l)
Accept equations for anaerobic respiration, such as C6H12O6 (aq) → 2C3H6O3 (aq)
Ignore ATP if added as a product.
\(n\left( {{{\rm{C}}_{\rm{6}}}{{\rm{H}}_{{\rm{12}}}}{{\rm{O}}_{\rm{6}}}} \right)\left\langle { = \frac{{15.0}}{{180.18}}} \right\rangle = 0.0833 \ll {\rm{mol}} \gg \)
«energy=0.0833×2803=»233«kJ»
Award [2] for correct final answer.
Accept -233«kJ».
Two advantages:
renewable resource
broken down/digested by bacteria or other organisms within a relatively short time/quickly
reduce «volume of» plastic waste/landfill
reduce use of petrochemicals
OR
reduce use of fossil fuels as hydrocarbon source
degrade into non-toxic products
Any two advantages for [2 max].
M2: reference must be made to time. Do not accept “biodegradable” (since stated in question).
Ignore any mention of cost.
Two disadvantages:
require use of land «for crop production»
increased use of fertilizers/pesticides «leading to pollution»
OR
eutrophication
might break down before end of use
release of methane/CH4/greenhouse gas «during degradation»
Any two disadvantages for [2 max].
Ignore any mention of cost.
typical curve as shown in example above √
Accept any curve with a single maximum (not just bell-shaped).
Ignore features such as pH values on a pH scale or a pH value at maximum (if given).
Do not penalize if curve does not touch the x-axis.
