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    May 2018
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  1. Usually for activities like that, your main CAS supervisor would be that supervisor and you would have to provide concrete evidence (like fitness logs, etc.) to them.
  2. I'm having trouble with the following question: Let P be a point on the wheel (which has a diameter of 100 m). The wheel starts with P at the lowest point, at ground level. The wheel rotates at a constant rate, in an anticlockwise (counterclockwise) direction. One revolution takes 20 minutes. What would be the height of P above ground level after 15 minutes? Thank you
  3. A driver of a car travelling on a straight slippery road sees a stop sign 50 m ahead and starts to break. After the breaks are applied, the velocity of the car is given by v(t)=11-t^(3/2). Will the car go beyond the stop sign? I'm specifically having trouble with determining the C value for the indefinite equation of displacement. Thanks!
  4. Which element forms more than one stable positive ion? A. Ca B. Cr C. Zn D. Ba The answer is B, but how? Thanks!
  5. Which compound can both be esterified and turn acidified potassium dichromate (VI) solution green? A. (CH3)3COH B. CH3CH2CO2H C. (CH3)2CHOH D. CH3CH2COCH3 The answer is C, but how? Thanks!
  6. Which molecule is non-polar? A. OF2 B. NH3 C. BF3 (answer) D. SO2 How do we know this without using the electronegativity values? Thanks!
  7. The graph below illustrates how the vapour pressures of ethoxyethane, CH3CH2OCH2CH3, benzene, C6H6, and water, H2O, change with temperature. Using data from the graph, explain the difference in vapour pressure of ethoxyethane, benzene and water at 30 °C. ANSWER: water has hydrogen bonding; benzene has van der Waals’/London/dispersion forces; ethoxyethane has dipole–dipole forces (and van der Waals’/London/ dispersion) but they are weaker than benzene I understand the forces of each of these substances BUT how does it relate to their positions on the graph? Thanks!
  8. Bromine was added to hexane, hex-1-ene and benzene. Identify the compound(s) which will react with bromine in a well-lit laboratory. Answer (according to markscheme): hexane AND hex-1-ene; Accept "benzene AND hexane AND hex-1-ene" I thought that the answer would be hex-1-ene and benzene as hexane is saturated (the bromine water test). Why is it not?
  9. Does the number of delocalized electrons equal the number of valence electrons for an atom? Thank you!
  10. On the IB Chemistry Syllabus (or any experimental science for that matter), there is a section that is titled "Utilization". It just refers to other practical links to the concepts in each chapter. Are we supposed to know these links for the actual exam? Thanks!
  11. What is the approximate pH of a 0.01 mol dm–3 ammonia solution? A. 2 B. More than 2 but less than 7 C. More than 7 but less than 12 D. 12 The correct answer is C. I know that A and B cannot be the answers but how would you do this question without actually doing the math as the answer could be C or D?
  12. The diagrams below represent equilibrium mixtures for the reaction Y + X2 ->/<- XY + X at 350 K and 550 K respectively. Deduce and explain whether the reaction is exothermic or endothermic. (350 K VS. 550 K) Thank you in advance!
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