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

2018 neco computer science questions and answers


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

 

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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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