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Neco Gce 2017 Chemistry Practical Answers – Nov/Dec Expo
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chidusky
chidusky (m)
1 year ago
NECO GCE - CHEMISTRY PRACTICAL ANSWERS
Exam Time: Wednesday, 30th October, 2017
Chemistry 3 (Alternative to Practical)
2.00am – 4.00pm
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(2ai)
INFERENCE:
Sample X is a soluble salt

(2aii)
OBSERVATION:
A gas is evolved. The gas turns red moist litmus blue.
It forms white fumed when NaOH solution was added was added

INFERENCE:
Alkaline gas

(2aiii)
INFERENCE:
CO3 gas is CO3^2-

(2aiv)
INFERENCE:
The solution is alkaline

(2av)
(NH4)2CO3(aq)+2NaOH(aq) >> Na2CO3(aq)+2NH3+2H2O(g)

2bi)
REAGENTS: Adition of KSCN Solution
(Fe2+): Pale-colouration
(Fe3+) Blood red colouration
2bii)
REAGENT: Addition of NaOH solution in drop till excess
(Fe2+): Dirty green gelatineous precipitaye which is insolube in excess NaOH.
(Fe3+): Reddish brown gelatineous precipitate which is insolube in excess NaOH.
2biii)
REAGENT: Addition of K2Fe(CN) solution
(Fe2+): It forms a dark blue precipitate
(Fe3+): A deep red colouration
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(1ai) Methyl Orange
Reason:- Titration of strong acid against base
(1aii) Yellow
(1aiii)Hydrochloricacid
(1aiv)2HCL(aq)+ x2Co3 -> 2 x CLaq + H20(aq) + CO2(g)

(1b) Molar mass of HcL = 1+35.5
=36.5gmol^-1
Con of A is moldm^-3 =
Con of A of gdm^3/molar mass in gdm^3
=7.30gdm^-3/36.5gmol^-1
=0.200moldm^-3

(1bii)
using CAVA/CBVB = a/b
CA = 0.200mol/dm^3
VA = 26.20cm^3
Cb = ?
VB = 25.0cm^3
a = 2mols
b = 1mol
0.200mol/dm^3 x 26.2cm^3/Cb x 25.0cm^3
= 2mols/1mol
Cb = 0.200x26.20x1/25.0x1
Cb = 5.24/25.0mol/dm^3
Cb = 0.2096mol/dm^3

(1biii)
Conc. of B in gdm-3/Conc. of B in mol/dm-3
=10.6gdm-3/0.148 gdm-3
=101.15g
=101gmol-1
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(3a)
(i)NH4CL and AgNo3
(ii)ZnCo3
(iii)Fes
(iv)AgNo3
(v)NH4Cl

(3b)
- Burrette
- Reshort Hand
- Solution/Acid
- Conical Flask
- white tile

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