NECO – CHEMISTRY – PRACTICALS – ANSWER
1 ai)
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|
1 ai)
average volume of Acid used
1 st + 2 nd + 3 rd / 3
14. 90+ 15. 00+ 15. 10/ 3 = 45/ 3 = 15cm^ 3
1 aii )
2 HCL ( aq ) + Na 2 CO 3 ( aq ) – – – – > 2 NaCl ( aq ) + H 2 O( aq ) + CO 2 ( aq )
1 bi)
CA VA / CB VB = NA / NB
0 . 1 moldm ^ – 3 * 15cm^ 3 / CB * 25cm^ 3 * 2 / 1
CB * 25cm^ 3 * 2 = 0 . 1 moldm ^ – 3 * 15cm^ 3 * 1
CB * 50= 1 . 5
CB = 1 . 5 / 50= 0 . 03moldm ^ – 3
1 bii )
25cm^ 3 – – – – > 0 . 03mole
1000cm^ 3 – – – – > x
x= 1000* 0 . 03/ 25= 30/ 25
x= 1 . 2 moldm ^ – 3
1 biii)
mold ^ – 3 = Con glm ^ 3 / molar mass
0 . 03moldm ^ – 3 = x/ 106
x= 0 . 03* 106
x= 3 . 18gldm ^ 3
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2 a )
Tabulate
2 ai)
– 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) CO 3 ^ – 2 ,SO4 ^ – 2 ,SO3 ^ 2 – suspected
iii ) CO 3 ^ 2 – ,SO3 ^ 2 – , suspected
2 bi)
– OBERSVATION-
i ) effervescence occurs with the evolution of a gas
ii) the solutions turns to pink
– INFERENCE –
i ) CO 3 ^ 2 – ,SO3 ^ 2 – , suspected
ii) CO 3 ^ 2 – ,Confrimed
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3 ai)
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.
3 aii )
i ) liquid substance – – > crystallization
ii) Solid substance – – > precipitation
3 bi)
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 .
3 bii )
Carbon ( iv ) oxide does not support combustion
3 ci )
molar solution is an aqueous solution that contains 1 mole ( gram – molecular weight ) of solute in 1 liter of the solution.
3 cii )
Indicator
3 ciii )
i ) methyl orange
ii) Phenolphthalein .
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Completed
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