NECO CHEMISTRY PRACTICAL ANSWERS 2021

NECO CHEMISTRY PRACTICAL ANSWERS 2021

Here is the neco chemistry practical answers for 2021. More answers will be posted, check back in few minutes and refresh.

Chemistry practical answers 2021

(1a)

Tabulate

Volume of pipette used=25cm3.

Indicator used= Methyl orange

Under Titration, Rough, 1st, 2nd, 3rd,

Final burette reading; |25.00| |23.40| |23.50| 23.60|

Initial burette reading; |0.00| |0.00| |0.00| |0.00|

Volume of A used; |25.00| |23.40| |23.50| |23.60|

(1ai)

Average volume of Acid used=23.40+23.50+23.60/3 =70.5/3=23.50cm3

(1aii)

This is because it is a reaction between a weak acid and strong base

(1aiii)

A funnel should be used while transferring the acid into the burette.

(1bi)

Conc of A in mol|dm³ =?

Conc of A in g|dm³ = 12.75g|dm³

Molar mass of A, NaHSO⁴ = 23+1+32+64

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=120g|dm³

From.

Conc(mol/dm³) = conc(g/dm³)/molar mass

Conc =12.75/120

Conc =0.106mol/dm³

(1bii)

Con of B in mol/dm³ =?

Ca =0.106, Cb =? Va =23.50cm³, Vb =25.00cm³

na=1 , nb=1

From; CaVa/CbVb=na/nb

Cb=CaVanb/Vbna

Cb=0.106*23*50*1/25.00*1

Cb=2.5/25

Cb=0.1mol/dm³

(1biii)

Conc of B in g/dm³=?

Molar mass of B , NaOH=23+16+1=40g/mol

From; conc(g/dm³)=conc(mol/dm³)*molar mass

=0.1*40

=4.0g/dm³

(1biv)

Mass of salt formed =?

Recall mole of NaHSO⁴=?

From; mole =con(mol/dm³)*vol(cm³)/1000

Mole=0.106*23.50/1000

Mole=0.0025mol of NaHSO⁴

By proportion 1mol of NaHSO⁴ produce 1mol of Na²SO⁴ 0.0025mol of NaHSO⁴ will produce X mol of Na²SO⁴ X=0.0025*1=0.0025mol of NaSO⁴

Molar mass of Na²SO⁴=(23*2) + 32 + (16*4)

=46+32+64

=142g/mol

Recall; mole =mole/molar mass

Mass =mole * molar mass

Mass =0.0025*142

Mass =0.36g of Na²SO⁴

(2a)

TEST

C + 5cm³ of distilled water

OBSERVATION

It dissolve completely

INTERFERENCE

C is a soluble salt

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(2bi)

TEST

Solution + NaOH + Heat

OBSERVATION

Effervescence occurs in which a colourless gas with pungent smell and turns red litmus paper to blue is given off.

INFERENCES

NH³ gas from NH⁴+ is present

(2bii)

TEST

Stirring rod of HCL + gas given off

OBSERVATION

a gas which gives a pop sound is given off

INFERENCES

H² is present

(2ci)

TEST

Solution C + drops of BaCL²

OBSERVATION

a white precipitate is formed

INFERENCES

CO²^-3, SO²^-4, SO²^-3, May be present.

(2cii)

TEST

Solution in C(i) + dil HCL

OBSERVATION

the white precipitate dissolve is dil HCL and effervescence occurs in which a colourless and odourless gas which turns blue litmus red and lime water milky is given off

INTERFERENCE

CO² gas from CO²^3- confirmed

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(3a)

(i)Ca²+

(ii)Pb²+

(3bi)

concentrated acid can be defined as an acid formed when a large quantity of an acid dissolve in a small or little volume of water.

(3bii)

A strong acid is defined as a type of acid that ionize completely in a solution

(3c)

Activated charcoal is used as an adsorbent material

(3d)

(i)Reddish – Brown

(ii) I – red, II – brown.

 

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