NECO GCE/ENDSARS CHEMISTRY PRACTICAL ANSWERS

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Neco


2021-NECO-GCE-CHEMISTRY PRACT-ANSWERS
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COMPLETED
1ai)
-inconsidtent reading of the burette to the nearest whole number
-consistently reading burette to one decimal number
-arithmetic error
-lack of unit
-non concordant values
1aii)
Average Titre=24.55+22.60+22.50/3
=69.65cm³/3
=23.216cm³
1aiii)
Na²Co3+2HCL===>2Nacl+H20+Co2
1aiv)
Methyl Orange.
1av)
It’s a titration Between strong acid and Strong Base
1avi)
Pink
1bi)
CA=0.0050moldm-³,Na=2
CB=? VB=25cm³, Nb=1
VA=23.21cm³
CAVA= NA
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CBVB NB
0.050X23.21=2
CBX25.00 1
CBX2X25.00=0.0050X23.21X1
CB=1.1605/50 moldm³
CB=0.023moldm³
1bii)
Molar mass of Na2 Co3
2[Na]+ C+3 [O]
=2(23)+12+3+(16)
=46+12+48 gmol-1
Molar Mass of Na2Co3=106gmol-1
Concentration Of Na2Co3 in gdm-3
=CBx Molar Mass
=0.023×106 gdm-3
=2.438gdm-1
1biii)
1 Mole Of Co2=22.4cmd-3
Mole Ratio Of B(Na2Co3):Co2= 1:1
0.023mole=0.023mole
1mole of Co2=22.4dm³
0.023mole =22.4×0.023
=0.52dm³
1biv)
n=CV
n=0.05×23.21
n=1.16mole
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NO2a)
Observation| Inference
i) | Fe³+Present
ii) | Fe³+ Present
iii)brown
Solution ——-
Observed
iv)Red blood Cell ———- Observed.
2b)
i) |Co3²-,So3²- S²- may Present
ii) | Co3²-,So3² S²- may present
Iii)
KmnO4 Decolour Rised
2c)
i)Effervescence of greenish-yellow gas turns blue litmus red
ii)The Precipitate dissolved…
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(3ai)
(i)To prevent sunlight Ray’s from affecting the solutions
(ii)To prevent the sucking back of water into the hot flask.
(iii) Because it is a component of glass
(iv)NaOH + CO² —> NaHCO³
(3bi)
(i)Heat iodine crystal
(ii)NH⁴Cl
(3bii)
(i)Stationary phase
(ii)Morning phase
3aiv) 2NaOH + SiO3 —–> NaSiO3 + H2O
Completed
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