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• NECO

Neco 2021 Chemistry Practical Questions And Answers

Posted by James on July 13th, 2021

WELCOME TO ONLINE NECO 2021 CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS SUBSCRIPTION

 

“”NECO JUNE/JULY 2021 CHEMISTRY PRACTICAL””

The Chemistry Practical Comprises 3 Questions from Volumetric or Titrimetric Analysis And General Questions. You are to Attempt all Questions.

Make sure you use your school Average Titration Values in other to get Accurate Solutions with your Lab. Attendant Report.

NUMBER 1 STEP 3 VOLUME OF THE A USED IS THE LAST POINT, AND EACH SCHOOL HAS HIS LAST POINT ,SO ASK YOUR CHEMISTRY TEACHER FOR THE LAST POINT AND THEN CALCULATE YOUR AVERAGE VOLUME OF ACID USED

(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
=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

(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
====================================

(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.

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

Completed!.

Note: Remember this, use your school end point to calculate number 1 question. Thanks

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