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Author Topic: Real WAEC Chemistry Obj and Theory (Essay) 2012 Questions and Answers  (Read 2832 times)

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2012 WAEC GCE CHEMISTRY OBJ AND THEORY ANSWERS ONLINE.

Verified Chemistry OBJ:
1-10: CDAACDAADA
11-20: BABDDDBADD
21-30: CBCCCBCDBC
31-40: DCBCCDBCCD
41-50: DBBCCBBCBA

THEORY ANSWERS
(1ai)Q and S 
(1aii)Q and T, S and U 
(1aiii) I. Q and S. II.by gaining electron is U. 
(1aiv) T 
(1av) S and U .
(1bi) Electronegative is the tendency of an atom to gain electron and become negatively charge.
(1bii) it increases across the period and decrease down group.
(1biii) due to additional shell, it increases down the group and due to additional electron, it decreases across the group because the nuclei pull between the proton in the nucleus and the valence increases.
(1c.)
(i)They have variable oxidation state
(ii)They have the ability to form coloured ion
(iii) They have the ability to form  complex ion.
(1di) 2KClO32KCl +3O2
(1dii) it serve as a catalyst and makes the reaction to occur at a lower temperature and at a faster rate.
(1diii) molar mass of KClO3=39+35.5+48=122.5g molar mass of KCl=39+35.5=74.5g. Mass of the chloride produced (15*2*74.5)/ (2*122.5),=9.122g

2ai Boyles law state that the volume of a given mass of a gas is inversely proportional to its pressure provided that the temperature remain constant
2aii)V (alpha)1/p
V= k/p, V1P1= V2P2
(2aiii)(1) it occurs at high temperature (2) also at low pressure 
(2aIV) (I) - gases are made up of molecules which are in constant random motion.
-The particles do not attract each other
-The  total volume actually occupied by the gas molecule is negligible compared with the volume of the container
(II) Dalton law of partial pressure state that the total pressure exerted by a mixture of gases is equal  to the sum of the partial pressure of each constituent provided the gases would not chemical react together.  i.e. PT= PA+ PB +PC+PD.
(2b)(i)  p - Condensation, Q- Freezing, R- sublimation
(ii)I- Sublimation,  II- Iodine molecule
 
(2c)t1/t2= (square root of ) m1/m2.
Rate of diffusion = vol/time
RCH4=  80/20=4
RQ=50/25=2
 
RCH4/RQ= square root of)  mQ/MRcH4
4/2=square root of) MQ/16 
4/2= square root of) MQ/4
Square root of MQ= 4 x 4/2= 16/2=8.
(2c.) t1/t2= (square root of ) m1/m2.
Rate of diffusion = vol/time
RCH4=  80/20=4
RQ=50/25=2
 
RCH4/RQ= square root of)  mQ/MRcH4
4/2=square root of) MQ/16 
4/2= square root of) MQ/4
Square root of MQ= 4 x 4/2= 16/2=8.

(3aI)An acid-base indicator is a weak organic acid or base which changes colour depending on the hydrogen ion concentration of the solution.
(II)a suitable indicator is one which its PH value(range)falls within the end point PH of the resulting solution of the acid-base reaction.
(III)(i)phenolpthalcim
(ii)the end poin PH solution is alkaline(strong acid against base)

(8a)
k-metallic bond
H2-covalent bond
KH-covalent bond
units which make up the subsctance 
k-kilojoule
H2-kilojoule
KH-kilojoule
 
(8bi) H20>H2>CH4
increasing order of boiling points
(8bii)
boiling points increase with the member of hydrogen bond.
(8di) it reacts with base to form salt and water, it react with metall to form hydrogen gas
(8dii) 
I-acidic
II--basic
III-acidic
Iv-acidic

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Offline kizeto

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 answer on dis number 08105947028 the no i use to register is my bro no now i need the weac gce 2013 answer for science

 

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