Call/WhatsApp: 09069072051 Welcome to Waec 2021 Chemistry Practical Answer
Welcome to Waec 2021 Chemistry Practical Answer as I Congratulations for your search here as NAIJACLASS is the Number one Trusted Exam Specialists, An expert in all Exams Sector; we assist candidates to pass various examinations with ease.
KNOW YOUR SCHOOL’S END POINT AND MAKE USE OF IT, IT MIGHT BE DIFFERENT FROM OURS.
WAEC 2021 CHEMISTRY PRACTICAL ANSWERS
(1a)
Volume of burrete = 50.00cm³
Volume of pipette = 25.00cm³
Indicator = Methyl orange
TABULATE
Final burette readings (cm³); 37.50 | 22.50 | 37.50 | 44.50
Initial burette readings(cm³); 0.00 | 0.00 | 0.00 | 0.00
Volume f Acid used (cm³); 37.50 | 22.50 | 22.50 | 22.50
Volume of A used = 1st + 2nd + 3rd/3
= 22.50+22.50+22.50/3
Average volume of A used = 22.50cm³
(1bi)
Concentration of A ( CA )?
2.03g in 500cm³ of solution
Volume = 500cm³/1000 = 0.500dm³
In g/dm³ = 2.03/0.5 = 4.06g/dm³
To find concentration in mol/dm³
Conc. of A in mol/dm³ = Conc. of A in g/dm³/Molar mass
Conc. of A in mol/dm³ = 4.06/36.5
= 0.1112mol/dm³
Molar mass of A (HCL) = 1+35.5 = 36.5g/mol
(1bii)
Number of mole of the Acid in average titre
Na = CaVa
= 0.1112 × 22.50
= 2.52moles
(1biii)
Nb= ? Na= 3, Ca= 0.1112mol/dm³, Cb = 0.12mol/dm³ , Va = 22.50cm³, Vb = 50.00cm³
CaVa/CbVb= nA/nB
0.1112×22.50/0.12×50 = 3/nB
nB × 2.502 = 18
nB = 18/2.502 =
:. nB = 7.194moles
= 7moles(approx.)
(1biv)
Mole ratio of Acid to base
nA:nB = 7:3
===============
3ai) The titre value would be higher than 23.50cm³.
3aii) This is because when distilled water was added to the base , the base becomes less concentrated , hence it’s easier to titrate than a concentrated base.
3bi) no reaction occurs , copper is less electropositive than Zinc , so cannot displace it in the reaction.
ii), KOH is a deliquescent compound, so it would absorb water from the atmosphere to form sticky particle in the watch glass.
III), when few drops of phenolphthalein is dropped in the watch glass , it changes colour to pink because it’s a basic solution (KOH).
(3c)
When NaOH is added to the solution of zn³+, a white precipitate is formed which later dissolve in excess NaOH due to the formation of zinc hydroxide
=======================
NUMBER 1
NUMBER 2
ABOUT US
Naijaclass is an online Platform; A subsidiary school news portal for aspirants, students, graduates and interested individual of various schools which kicked off July 1st, 2014 with an aim of providing useful and valuable information about Higher Institutions News, Online CBT Practice for Waec, Neco, Nabteb & Jambite, Scholarships, Study-abroad, health, Career and much more to students at all levels of education to happy visitors About us in Nigeria and in the diaspora.
Be the first to comment