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Ees413:Aquatic Chemistry Question Paper

Ees413:Aquatic Chemistry

Course:Aquatic Chemistry

Institution: University Of Eldoret question papers

Exam Year:2014

Answer all questions in section A and any four in section B
SECTION A
1.Construct the equation for the reaction between manganate(VII)ions and iron(II)ions in aqueous acidic solution.[4marks]
2.Integrate the differential equation for the first-order reaction rate[3marks]
3.Specify the units in for all quantities involved in the equation Q2?[2marks]
4.Urea,NH2CONH2,is an important agricultural chemical.
The following are STD enthalpies of formation at 25C for the reactants and products(kJ/mol):
NH3(g),-45.9;CO2(g),-393.5;NH2CONH2(aq),-319.2;H2O(l),-285.8
Calculate the H of the reaction[3marks]
5.Explain the meaning of the term''amphiprotic species''?[3marks]
6.Given that the pOH of an aqueous solution is 8.Calculate its pH[2marks]
7.What is a Lewis acid?Illustrate your answer using the reaction between Al3+ and H2O[3marks]
8.What is the pH of a solution whose hydroxide ion concentration is 4.0x10^-4 mol/L?Is the solution acidic or basic?[3marks]
9.Silicate is basically a compound of silicon and oxygen with one or more metals that may be formally regarded as a derivative of silicic acid in aqueous solution.Write down the condensation reaction of silicic acid anions[3marks]
10.Illustrate graphically the buffering effect of CO2 in natural waters[4marks].
SECTION B
11.Briefly describe the following variables that affect chemical reaction rate in aquatic environment:
a.Physical state[4marks]
b.Concentration[3marks]
c.Temperature[3marks]
12.Using CaC2O4 and CaCl2 as an example:
a.Show the importance of solubility constant (Ksp) and the common ion effect at equilibrium [5marks]
b.What is the molar solubility of calcium oxalate in 0.15M calcium chloride?(Ksp for CaC2O4(s) is 2.3x10^-9) [5marks]
13.Organic matter arising from living organisms makes an important contribution to the natural quality of surface waters.Describe:
a.Formation,and composition of humic acids in natural waters[6marks]
b.Chemical characteristics of humic substances[4marks]
14.Henderson-Hasselbalch equation may be used,among other things,in the preparation of buffer solutions of known pH:
A.Derive Henderson-hasselbalch equation [6marks]
B.Given that Ka of the conjugate acid NH4+ is 5.6x10^-10,calculate the pH Of a buffer solution containing 0.10MNH3 and 0.20MNH4Cl at 25 C.[4marks]
15.Eldoret wastewater stabilization pond initial organic load measurements show a BOD concentration of 200mg/L.Three days later the BOD concentration is 100mg/L.
a.Calculate the BOD concentration in the pond after a week(assume biodegradation rate is first-order reaction).[4marks]
b.How long will it take for the BOD concentration levels to reach the Kenyan effluent discharge standard requirement concentration levels to reach the Kenyan effluent discharge standard requirement concentration level?[3marks
]
c.Plot the BOD concentration against time (Graph paper provided)[3marks]
16.Briefly describe the hydrological cycle.[10m]

Ees413:Aquatic Chemistry Question Paper

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