NECO 2018 Chemistry Practical Answer – June/July Expo

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AYOSTUFFS/A2 SOLUTIONS

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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|

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1ai)

average volume of Acid used

1st+2nd+3rd/3

14.90+15.00+15.10/3=45/3=15cm^3

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1aii)

2HCL(aq)+Na2CO3(aq)—->2NaCl(aq)+H2O(aq)+CO2(aq)

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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

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1bii)

25cm^3—->0.03mole

1000cm^3—->x

x=1000*0.03/25=30/25

x=1.2moldm^-3

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1biii)

concentration in mold^-3 =Con glm^3 /molar mass

0.03moldm^-3=x/106

x=0.03*106

x=3.18gldm^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

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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

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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.

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3aii)

i)liquid substance–> crystallization

ii)Solid substance–> precipitation

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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.

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3bii)

Carbon(iv)oxide does not support combustion

 ==========Ayostuffs============

 3ci)

molar solution is an aqueous solution that contains 1 mole (gram-molecular weight) of solute in 1 liter of the solution.

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3cii)

Indicator

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3ciii)

i)methyl orange

ii)Phenolphthalein.

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Completed

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