CHAPTER 3. REACTION RATES 3.9
Time elapsed (min) Vol of H 2 (g) (cm^3 )
0 0
0.5 17
1.0 25
1.5 30
2.0 33
2.5 35
3.0 35
i. Plot a graph of volume versus time for these results.
ii. Explain the shape ofthe graph during the following two time
intervals: t = 0 to t = 2.0 min and then t = 2.5and t = 3.0
min by referring to the volume of H 2 (g) produced.
(IEB Paper 2, 2001)
- Cobalt chloride crystals are dissolved in a beaker containing ethanol
and then a few drops ofwater are added. After aperiod of time, the
reaction reaches equilibrium as follows:
CoCl^24 −(blue) +6H 2 O� Co(H 2 O)2+ 6 (pink) +4Cl−
The solution, which is now just blue, is pouredinto three test tubes.
State, in each case, what colour changes will beobserved (if any) if
the following are addedin turn to each test tube:
(a) 1 cm^3 of distilled water
(b) A few crystals of sodium chloride
(c) The addition of dilute hydrochloric acid tothe third test tube
causes the solution to turn pink. Explain why this occurs.
(IEB Paper 2, 2001)
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