1. D
2. A
3. D
4. C
5. C
6. A
7. A
8. B
9. C
10. B
11. C
12. C
13. C
14. D
15. D - (a bit ambiguous)
16. D
17. A
18. B
19. B
20. B
ER
1a) Measure the volume of CO2 gas produced over time (other viable answers accepted)
b) i. Surface area vs reaction rate
ii. The reaction will be faster in beaker A. There is increased concentration of HCl in beaker A, and is hence denser than that of solution B - more collisions will occur as a result of the limited space in beaker A, producing more fruitful collision and hence a higher reaction rate
c) Collision theory states that a successful reaction results from a collision only when particles have the energy to overcome activation energy as well as collide in a favourable orientation. Since temperature is only a measure of average kinetic energy, some particles will not have enough energy to overcome the activation energy and if they collide no reaction will ensue. Hence the statement is incorrect.
2a) (CH3)3Br(aq) + OH- (aq) -----> (CH3)3COH (aq) + Br-(aq)
b) i. Step 1 is endothermic. The activation energy is higher than that of the energy released upon formation - hence the net energy change is an absorption of energy and hence is endothermic.
ii. Step 1 should be slower due to the higher activation energy required.
3a) Weak acid is an acid that doesn't ionise completely in solution
b) i. Malic acid is a weak diprotic acid as it has two carboxylic acid; two Ka values refer to the acidic constant of each dissociation
ii.HOOCCH2CH(OH)COO- (aq) + H2O (l) <----> (O-)OCCH2CH(OH)COO- + H3O+ (the brackets means that the O and minus are together)
c) The addition of HCl will act to neutralise the OH- in the equilibrium solution - effectively rendering a decrease in the concentration of OH-. Le Chatelier's principle states that a system will aim to partially oppose a change that is applied to it. The decrease in product will prompt a forward reaction to increase the amount of product in equilibrium. Hence the concentration of sorbic acid will increase.
d) pH = 4.76. [H3O+] = 10^-4.76 = [sorbate]
Ka = 1.73 x 10-5 = [hydronium][sorbate]/[sorbic]
[sorbic]equilbrium = 1.74 x 10^-5
Ionisation = [sorbate]equilbrium/[sorbic]initial [sorbic]initial = [sorbic] equilibrium + [sorbate] equilibrium
Ionisation is approximately 50%.
4a) The K value of the equilibrium is so small (smaller than 1 x 10^-4), which suggests that at equilibrium very few products will have formed as K value is [products]/[reactants]. Insignificant amounts of COCl2 have decomposed to form CO and Cl2 - hence we can assume that the concentration of COCl2 at equilibrium is roughly equal to its initial concentration
b) i. [CO][Cl2]/[COCL2] = 2.1 x 10^-8. [CO]=[Cl2] as they are produced in a 1:1 mole ratio.
[COCl2] = 0.33M
Therefore [CO]^2 = 2.1 x 10^-8 x 0.33
[CO] = 8.4 x 10^-5 M
ii. [Cl2] = 8.4 x 10^-5 M
Sulfuric acid
5a) Production of fertiliser is the main one. Other uses accepted (strong acid, etc)
b) i. Production of sulfur dioxide can induce the formation of acid rain
ii. Double pass procedure is used to convert as much sulfur dioxide to sulfur trioxide and hence limit the emission of sulfur dioxide into the atmosphere.
6a) i. 5.25 x 180 x 1.5 / 0.593 = 2390.38J/C = 2.39kJ/C
ii. 2.39kJ/C x 8.63 = 20.62kJ of energy released by 0.934 grams of methanol.
n(CH3OH) = 0.934/32 = 0.0292 mol
delta H = -2E/n = 1.41 x 10^3 kJ/mol (unsure of answer cos its worth 5 marks..)
b) Calorimeter not insulated
Incomplete combustion
Anything that would make the water absorb less energy than calculated.
A stiffer answer but... i don't see why not..
The value in the databook refers to the reaction of methanol in which the co-efficient in front of methanol is 1. There is 2 in the equation in part a.ii. and hence the value is approximately twice as large.
c) i. O2 + 4H+ + 4e- ----> 2H2O
ii. Less energy is required for power to be produced so that the small appliances don't overheat.
7a) CH3COOH + 2H2O ----> 2CO2 + 8H+ + 8e-
b) right
c) O2 + 4H+ +4e- ----> 2H2O
d) Electrolysis cell converts electrical energy to chemical, fuel cell produces electrical from chemical.
8a) i. 36/5 x = 7.2 tonnes.
ii. 7.2 tonnes x 40% = 2.88 tonnes of carbon/12 = 240000mol of carbon
n(CO2) = 240000mol
m (CO2) = 11 tonnes.
b) Water takes up a large majority of the mass
Also coal with water doesn't combust as well.
9a) 2Br- ----> Br2 + 2e-
b) Q = 1.5 x 1800 = 2700
n(e-) = 2700/96500 = 0.0279
n(X) = n(e-)/2 = 1.40 x 10^-2 mol
c) 2.9/ 1.40 x 10^-2 mol = 207.3 = molar mass
Metal is lead.
Home
Help
Search
Login
