Neco 2018 Chemistry Practical Expo

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(1a)
Tabulate:

Titrations |Rough|1st |2nd |3rd |
Final burette reading |18.00|15.60|17.40|20.50|
Initial burette reading |0.00 |0.00 |2.00 |5.00 |
volume of Acide used |18.00|15.60|15.40|15.50|
(1ai)
Average volume of Acid used
VA = (VA1 + VA2 + VA3)cm3/3
VA = (15.60+15.40+15.50)/3
VA = 46.50/3
VA = 15.50cm3
(1aii)
2HCl(aq)+Na2CO3(aq)–>2NaCl(aq)+H2O(l)+CO2(g)

(1bi)
CA VA/CB VB =NA/NB
0.1moldm^-3 x 15.50cm3/CB x 25cm3 x 2/1
CB x 25cm3 x 2 = 0.1moldm^-3 x 15.50cm3 x 1
CB x 50 = 1.55
CB = 1.55/50 = 0.031moldm^-3

(1bii)
25cm^3—->0.031mole
1000cm^3—->x
x=1000*0.031/25=31/25
x=1.24moldm^-3

(1biii)
concentration in mold^-3 =Con glm^3 /molar mass
0.031moldm^-3=x/106
x=0.031*106
x=3.286gldm^3

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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.














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