1. (a) Define
activation energy. Rate constant for a specific reaction is 2.52 x 10-5
s-1 at temperature 463 K and 6.30 x 10-4 s-1
at temperature 503 K. Calculate activation energy for that reaction.
[3 Marks]
(b)
At
certain temperature, ethanal decomposes according to following equation;
CH3CHO (g)
→ CH4 (g) + CO (g)
Base
on the graph above, calculate the activation energy for the decomposition of
ethanal.
[4 Marks]
(c) Below is a Maxwell-Boltzmann
distribution curve.
Briefly explain effect of temperature on
reaction rate.
[3 Marks]
2 When
23.4g sodium chloride was dissolved in 250 cm3 distilled water, the
temperature of the solution decreased by 2.2 oC.
(Specific
heat capacity of solution is 4.20 Jg-1 oC-1 , density
of H2O is 1 gcm-3)
(a) Define enthalpy of solution.
(b) Calculate
number of moles of sodium chloride used.
(c) Calculate
the enthalpy of solution of sodium chloride.
(d) Write
the thermochemical equation for sodium chloride solution.
[10 marks]
3. a) Define Faraday’s first law [2
marks]
b) A technician is
plating (saduran) a faucet (paip sink) with chromium from an electroplating
bath containing aqueous Cr2(SO4)3. If the process
of plating is allowed for 12.5 min and the rate of plating is 0.0688 gmin-1 as in figure below,
 |
i) Determine the mass of chromium deposited [1
mark ]
ii) Determine the moles of electron transferred [3
marks]
iii) Calculate the
charge carried by the electron transferred [2
marks]
iv) Calculate the current needed. [2
marks]
4.a.) Structural formula of compound for
screening the skin from the sunlight is given as follows:
i) Circle and
name 3 of the functional groups in the above structure.
[3 marks]
ii)
There are two
isomers of the substance. Draw both of the isomer structures.
[2 marks]
iii)
Name the type of
isomerism and explain how it could happen.
[2 marks]
b.) Based on the following reaction:
Cl
CH3C=CHCH3 +
HCl ¾® CH3
¾ C ¾ CH2CH3
CH2CH3 CH2CH3
i)
State the type
of reaction that occurred.
[1 mark]
ii)
Identify whether
the alkene used in the reaction can exist as geometrical isomers.
[1 mark]
iii)
What type of
bond cleavage happened in HCl. [1 mark]
SOALAN TAMAT
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