Free 2018/2019 neco chemistry questions and answers expo/runz

Free 2018/2019 neco chemistry questions and answers expo/runzFree 2018/2019 neco chemistry questions and answers expo/runz

 

2018 NECO CHEMISTRY PRACTICAL ANSWER
 
 
1ai)
Tabulate
Titrations|Rough|first(1)|second(2)|third(3)
Final burette reading-|20.50|14.90|15.00|15.10|
initial burette reading- |0.00|0.00|0.00|0.00|
volume of Acide used- |20.5|14.90|15.00|15.10|
 
1ai)
average volume of Acid used
1st+2nd+3rd/3
14.90+15.00+15.10/3=45/3=15cm^3
 
1aii)
2HCL(aq)+Na2CO3(aq)—->2NaCl(aq)+H2O(aq)+CO2(aq)
 
1bi)
CA VA/CB VB =NA/NB
0.1moldm^-3*15cm^3/CB*25cm^3 *2/1
CB * 25cm^3*2=0.1moldm^-3*15cm^3*1
CB * 50=1.5
CB=1.5/50=0.03moldm^-3
 
1bii)
25cm^3—->0.03mole
1000cm^3—->x
x=1000*0.03/25=30/25
x=1.2moldm^-3
 
1biii)
concentration in mold^-3 =Con glm^3 /molar mass
0.03moldm^-3=x/106
x=0.03*106
x=3.18gldm^3
 
================================
 
2a)
 
*Tabulate*
 
2ai)
*OBSERVATION:*
 
i)C dissolves in water
 
ii)formation of white precipitate
 
iii)White precipitate dissolves in itel
 
*INFERENCE:*
 
i)C is soluble in water
 
ii)CO3^-2,SO4^-2,SO3^2- suspected
 
iii)CO3^2-,SO3^2-, suspected
 
2bi)
*OBERSVATION:*
 
i)effervescence occurs with the evolution of a gas
 
ii)the solutions turns to pink
 
*INFERENCE:*
i)CO3^2-,SO3^2-, suspected
 
ii)CO3^2-,Confrimed
 
================================
 
3ai)
Zinc chloride reaction with HaOH form white gelatinous precipitate solution in excess HaOH.
Ammonium trioxocarbonate(iv) on reaction with HaoH evolves a gas which turns red litmus paper blue and lime water milky. Calcium trioxocarbonate(iv) on reaction with HaoH forms white powdery precipitate insoluble in excess HaOH.
 
3aii)
i)liquid substance–> crystallization
ii)Solid substance–> precipitation
 
3bi)
i)Evaporation takes place at all temperatures, while boiling occurs at a particular temperatur (at boiling point).
ii)Evaporation takes place from the surface, whereas the entire liquid boils.
 
3bii)
Carbon(iv)oxide does not support combustion
 
3ci)
molar solution is an aqueous solution that contains 1 mole (gram-molecular weight) of solute in 1 liter of the solution.
 
3cii)
Indicator
 
3ciii)
i)methyl orange 
ii)Phenolphthalein.
 
================================
 
*Completed*

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