NECO Chemistry practical answers 2020

NECO Chemistry practical answers 2020

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Indicator used is methyl orange.
Volume of pipette used is 25cm³

Titration; Rough|1st|2nd|3rd|

Final burette reading cm³|23.50|23.00|23.00|33.00|

Initial burette reading cm³| 00|0.00|0.00|10.00|


Volume of acid used(cm³) |23.50|23.00|23.00|23.00|

Average volume of A used = 23.00+23.00+23.00/3 =23.00cm³

Equation for the reaction

Concentration of A in moldm³ =concentration in gldm³.

3.6g of A =500cm²
Xg of A will be = 10000³
Xg=3.65*1000/500 =36.5/5 =7.3gldm³

Molar Mass of A HCl=1+35.5=36.5
Concentration of A =7.3gldm³/36.5gldm³

Concentration of B in moldm³
concentration of A in moldm³ CA=0.20
Volume of used VA=23.00
Concentration of B in moldm³ CB=?
Volume of B used VB= 25.00

CAVA/CBVB = n(A)/n(B) =2/1




Molar mass of B in glmol
Concentration of B(moldm-³)= conc gldm³/molar mass
0.092=10.60gldm³/molar mass
0.092 * molar mass =10.60gldm³
Molar mass =10.60gldm³/0.092

Relative atomic mass of X in X²CO³

TEST; C + 5cm³ of distilled water and shake thoroughly. Divide the solutions into three portions.

OBSERVATION; A pale green solution results

INFERENCE; salt is soluble

TEST; To the first portion add NaOH solution in drys

OBSERVATION; Dark green gelatinous was formed

INFERENCE; Fe²^+ present

TEST; then in excess

OBSERVATION; precipitate is insoluble

INFERENCE; Fe²^+ present


TEST; To the second portion add K3Fe(CN)6 solution

OBSERVATION; A dark blue precipitate formed

INFERENCE; Fe²^+ confirmed

TEST; To the third portion add AgNO³ solution

OBSERVATION; White Precipitate formed

INFERENCE; SO4²^- , CL^- CO²^- present

TEST; To the results obtained in add dilute HNO3 in drops , then excess

OBSERVATION; White Precipitate is insoluble

INFERENCE; CL^- present


TEST; To the results obtained in add NH3 solution

OBSERVATION; White Precipitate dissolves

INFERENCE; CL^- Confirmed



I. Methyl Orange
II. Methyl orange
III. Phenolphthalein

A white Precipitate is observed. Effervescence occurs a gas is evolved which change lime water milky.

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