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# 2020 PRACTICAL CHEMISTRY ANSWERS POSTED HERE

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2020 PRACTICAL CHEMISTRY ANSWERS POSTED HERE ðŸ‘‡

(1)

Indicator used is methyl orange.

Volume of pipette used is 25cmÂ³

Tabulate.

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

Volume of acid used(cmÂ³) |23.50|23.00|23.00|23.00|

Average volume of A used = 23.00+23.00+23.00/3 =23.00cmÂ³

Equation for the reaction

XÂ²CoÂ³(aq)+2HCl(aq)â€”->2XCl(aq)+HÂ²O(s)+Cl(s)

(1i)

Concentration of A in moldmÂ³ =concentration in gldmÂ³.

3.6g of A =500cmÂ²

Xg of A will be = 10000Â³

Xg=3.65*1000/500 =36.5/5 =7.3gldmÂ³

Molar Mass of A HCl=1+35.5=36.5

Concentration of A =7.3gldmÂ³/36.5gldmÂ³

=0.20moldmÂ³

(1ii)

Concentration of B in moldmÂ³

concentration of A in moldmÂ³ CA=0.20

Volume of used VA=23.00

Concentration of B in moldmÂ³ CB=?

Volume of B used VB= 25.00

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

0.20*23.00/CB*25.00=2/1

2*CB*25.00=0.20*23.00*1

CB=0.20*23.00/50

Cb=46/50=0.092moldm-Â³

(1iii)

Molar mass of B in glmol

Concentration of B(moldm-Â³)= conc gldmÂ³/molar mass

0.092=10.60gldmÂ³/molar mass

0.092 * molar mass =10.60gldmÂ³

Molar mass =10.60gldmÂ³/0.092

=115.2glmd

(1iv)

Relative atomic mass of X in XÂ²COÂ³

XÂ²+12+3(16)=115.2

2x+12+48=115.2

2x+60=115.2

2x=115.2Ã·60

2x=55.2

x=55.2/2=276

====================================

(2i)

Tabulate.

TEST; C + 5cmÂ³ of distilled water and shake thoroughly. Divide the solutions into three portions.

OBSERVATION; A pale green solution results

INFERENCE; salt is soluble

(2ii)

TEST; To the first portion add NaOH solution in drys

OBSERVATION; Dark green gelatinous was formed

INFERENCE; FeÂ²^+ present

(2iii)

TEST; then in excess

OBSERVATION; precipitate is insoluble

INFERENCE; FeÂ²^+ present

(2iii)

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

OBSERVATION; A dark blue precipitate formed

INFERENCE; FeÂ²^+ confirmed

(2iv)

TEST; To the third portion add AgNOÂ³ solution

OBSERVATION; White Precipitate formed

INFERENCE; SO4Â²^- , CL^- COÂ²^- present

(2v)

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

OBSERVATION; White Precipitate is insoluble

INFERENCE; CL^- present

(2vi)

TEST; To the results obtained in add NH3 solution

OBSERVATION; White Precipitate dissolves

INFERENCE; CL^- Confirmed

====================================

(3ai)

Filtration

(3aii)

Diagram.

(3bi)

I. Methyl Orange

II. Methyl orange

III. Phenolphthalein

(3bii)

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

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Posted by on October 22, 2020.

Categories: Neco