Wednesday 6th June 2018
Practical – Chemistry – 10:00am – 12:00noon
Practical – Chemistry – 10:00am – 12:00noon
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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
(2a)
Tabulate
(2ai)
OBSERVATION: C dissolves in water
INFERENCE: C is a soluble salt
(2aii)
OBSERVATION: White precipitate formed
INFERENCE: CO3²-, SO3²-, SO4²- suspected
(2aiii)
OBSERVATION: White ppt dissolves in excess of dil HCl
INFERENCE: CO3²- , SO3²- suspected
(2bi)
OBERSVATION: Effervescence occurs with the evolution of a gas
INFERENCE: CO3²- present
(2bii)
OBERSVATION: Solutions turns to pink
INFERENCE: CO3²- Confirmed
(3ai)
Zinc Chloride(ZnCl2) solution reacts with NaOH(aq) to form white ppt in drops. The precipitate dissolves in excess of NaOH.
Sodium hydroxide reacts with ammoniumtrioxocarbonate(iv) to form a solution which turns red litmus paper blue.
Calcium trioxonitrate(v) Ca(NO3)2 on reaction with sodium hydroxide forms a white powder precipitate insoluble in excess NaOH(aq)
(3aii)
I. Liquid substances - Boiling point of the substances.
II. Solid substances - The melting point of the substance.
(3bi)
(i) Evaporation takes place at almost all temperatures, while Boiling takes place at a specific temperature.
(ii) Only the surface of a liquid is involved in evaporation while the entire mass of the liquid is involved in boiling.
(3bii)
Carbon(iv)oxide does not support combustion.
(3ci)
A molar solution is an aqueous solution that contains one mole of solute in 1000cm³ of the solution.
(3cii)
Indicator.
(3ciii)
(i) Methyl orange
(ii) Phenolphthalein
(3ai)
Zinc Chloride(ZnCl2) solution reacts with NaOH(aq) to form white ppt in drops. The precipitate dissolves in excess of NaOH.
Sodium hydroxide reacts with ammoniumtrioxocarbonate(iv) to form a solution which turns red litmus paper blue.
Calcium trioxonitrate(v) Ca(NO3)2 on reaction with sodium hydroxide forms a white powder precipitate insoluble in excess NaOH(aq)
(3aii)
I. Liquid substances - Boiling point of the substances.
II. Solid substances - The melting point of the substance.
(3bi)
(i) Evaporation takes place at almost all temperatures, while Boiling takes place at a specific temperature.
(ii) Only the surface of a liquid is involved in evaporation while the entire mass of the liquid is involved in boiling.
(3bii)
Carbon(iv)oxide does not support combustion.
(3ci)
A molar solution is an aqueous solution that contains one mole of solute in 1000cm³ of the solution.
(3cii)
Indicator.
(3ciii)
(i) Methyl orange
(ii) Phenolphthalein
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