Posted on: 02:48 Mon, 11 Jun 2018



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Exam Time: Tuesday 12th June 2018
OBJ & Essay – Chemistry – 10:00am – 1:00pm
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CHEMISTRY OBJ:-
1-10: DADBCADBCA
11-20: DCDBDBEDDC
21-30: CBDEDBAAEA
31-40: ECCADAEDEB
41-50: EAADDACBBC
51-60: ADDDBACBEB
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CHEMISTRY THEORY ANSWER:-

(1a)
I. isotopy is a phenomenon whereby an atom of an element excite different mass number but have the same atomic number.
II. isomerism is existent of two or more compound (known as isomers) with the same molecular formulae but different molecular structure

1aii)
i)Deuterium
ii)tritium'

1bi)
CLICK HERE FOR THE DIAGRAM
Bottomed flask and set up the apparatus as shown. Add conc HCl gradual into the flask through the thistle funnel pass the gas produced through water and concentrated tetraoxosulphate (iv) and collect it by downward delivery.
2KMnO4(aq)+16HCl---->2MaCl2(aq)+8H2O(s)+5Cl2(aq)

1bii)
i)it is use as a bleaching agent
ii)it is use as disinfectant in the treatment of water
iii)it is use as an oxidizing agent

1ci)
GIVEN
P1=(745-13.5)mmHg =731.5mmHg
T1=(16+273)k=289k
P2=S.P=760mmHg
T2=S.T=273k
V1=40cm^3
using the general gas equation
P1V1/T1=P2V2/T2
V2=731.5*40*273/760*289
V2=36.4cm^3
the volume of the gas at S.T.P is 36.4cm^3

1cii)
i)Nature of reactions
ii)presence of a catalyst

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2a)
A=1s^2,2s^2,2p^6,3s^2,3p^5
B=1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3^9

2aii)
i)it is very mulleble
ii)it is an excellent conductor of heat and electricity
iii)it a red solidd with lustre

2aiii)
the oxidation state is -1

2b)
i)mecury
ii)propan 1, 2diol
iii)poly ethene

2c)
i)iron(iii)trioxocarbonate(iv)
ii)Zinc sodium hydroxide 
iii)2Chloro but - 3 diene

2d)
i)Chalk- calcium carbonate
ii) glass- silica sand
iii) ceramics- kaolin/iron oxide/aluminum or sodium carbonate

2ei)
Faraday first law of electrolysis state that the mass of an element or substance (m) liberated at the electrode during electrolysis is directly proportional to the quantity of electricity (N) passing through it.
Q where M=mass, Z is constant, I is current 

2eii)
4OH---->2H2O+O2+4e
from the oxidation half reaction of acidified water above it can be reduced that 4moles of electrons result to the formation of 1mole of oxygen
;4F=4*96,500C=386000
I=2.5A
t=1.5*60=90second
Q=It=2.5*90=225C
;386000 require 22.4dm^3
225c will require 22.4*22.5/386000
=0.0131dm^3
or 13.10cm^3

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3ai)
A homologous series is a family of organic compound which follows a regular structural pattern in which each successive member differ in its molecular formula. By-CH2-GROUP

3aii)
i)solubility
ii)boiling points
iii)densities

3aiii)
CLICK HERE FOR THE DIAGRAM

3bi)
catalyst are substance which alter the rate of a chemical reaction but not themselves used up in the process.

3bii)
i) they are proteinous in nature 
ii)they alter the rate of a chemical reaction
iii)they are not use themselves up in the reaction

3ci)
The solution turn from blue to white as a magnesium displace copper from its salt

3cii)
Mg(aq)+CuSO4(aq)-----> MgSO4(aq)+ Cu(s)

3di)
Equation Reaction:
2Na(s)+O2(q)----->Na2O2(s)
Number of moles of soduim =mass/molar mass =5.95/23=0.2587moles
reactive ratio of sodium to its oxide is 2:1
therefore number of moles of Na2O2=0.2587/2=0.129moles
mass of oxide 
=0.129*[(23*2)+(16*2)]
=0.129*78
=10g

3dii)
i)dissolving an acid on hydride in water
ii)combination of constituent element

3diii)
washing soda (NaCO3. 10H2O)

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4ai)
From the collision theory the rate of chemical reactions depend on the frequency of effective collisions cones that the result in reaction between reactant particles

4aii)
cracking means breaking down or decomposition of a compound by the action of heat alone. while Reforming is the breaking down of a compound by the use of a catalyst

4aiii)
they are the most important processes for the commercial production of gasoline and diesel fuel

4bi)
I. Limestone: the limestone decomposes when heated to yield carbon(iv)oxide which is a major reactant

II. Ammonia: The ammonia reacts with the carbon(iv)oxide ammonium hydrogen trioxocarbonate(iv)

4bii)
I. B belong to the class of compound called carbohydrates

II. C is ethanol [C2H5OH] , D is ethylethanoate [CH3COOC2H5]

III. Functional group is -OH

IV. CH3COOH(aq)ethanoic acid + C2H5OH(aq)c ----->conc H2SO4(catalyst) -----> CH3COOC2H5(i) + H2O(i)

4ci)
CH(CH3)3,CH3CH2CH2CH3,CH3CH2CH2CH2OH/Increasing boiling points

4cii)
i)Bubbles formed at the bottom of liquid rise to the surface

ii)temperature remain steady

4ciii)
I. Addition of sodium chloride crystals raises the boiling point of water
II. Reduction in atmospheric pressure lowers the boiling point of water

4civ)
I. N2O has oxidation state of +1 for Nitrogen
II. NO has oxidation state of +2 for Nitrogen
III. NO2 has Oxidation state of +4 For Nitrogen

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6ai)
NH4^+(aq)+OH^-(aq)+HCl(aq)---> NH4Cl(aq)+H2O(i)

6aii)
the student got the choice of indicator wrong

6aiii)
phenolphthalein is used when a strong base is present. aqueaous ammonia is a weak base

6b)
i)gluclose and fructose
ii)invertase
iii)delivery tube
iv)glucose

6ci)
white phosphorus and red phosphorus

6cii)
I. has no effect of red litmus paper
II. changes damp blue litmus paper pink
III. Reacts directly with alkali to yield a trioxocarbonate(iv)

6di)
GIVEN:
mass of P= 9g
molar mass of P =80g/mol
: Number of mole of P presnt =mass/molar mass
=9/80=0.1125moles
solubility =0.1125/60*100=1.875mol/dm^3

6dii)
C2H5OH(aq) +H2SO4(aq)----> C2H5HSO4(aq)+H2O(i)
C2H5HSO4(aq)---->C2H4(aq)+H2SO4(aq) ethene

6diii)
Bromine Exists as liquid at room temperature because there is decrease in votality down the group of the halogens due to increasing strength of the van der waal's force.




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