2019 Neco Gce Chemistry Practical Answers

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(2ai)
OBSERVATION: Thre is water droplets around the test tube. It is colourless and odourless. It turns white anhydrous copper II tetraoxosulphate VI blue. It is neutral to litmus

(2aii)
INFERENCE: Fe²+, Cu²+ are suspected

(2aiii)
INFERENCE: SO4²-, CO3²-, and SO3²- are present

(2aiv)
INFERENCE: SO4²- present

(2bi)
INFERENCE: Dehydration of organic salt occurs

(2bii)
INFERENCE: Reducing sugar ie glucose is present

(2biii)
INFERENCE: Reducing sugar ie glucose is confirmed

(3a)
-Filtration removes Pb(SO4)2
-Sublimation removes NH4Cl
-Filtration and evaporation is used to recover NaCl

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(3bi)
V1 = 50.0cm³
C1 = 0.05moldm
C2 = 0.01
C1V1 = C2V2
Using dilution formula
0.05×50 = 0.01×V2
V2 = 0.05×50/0.01 = 250cm³

Hence volume of water that should be added
V = V2 – V1 = 250 – 50 = 200cm³

(3ci)
Shine a beam of light to each of solutions of glucose and starch. Starch will disperse the ray of light (Tyndall effect) while glucose will not.

(3cii)
I – Physical test: Shine a beam of light to each of solutions of glucose and starch. Starch will disperse the ray of light (Tyndall effect) while glucose will not.

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II – Chemical Test: Use Benedict’s solution on starch; No positive result WHILE on glucose, It shows a positive test of brick red or orange colour.

(3ciii)
Ammonia gas

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