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2021 Neco free chemistry midnight answer/ Neco free expo

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Please ensure that you use your school Average Titration Values in other to get Accurate Solutions with your Lab. Attendant Report.
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(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|
 
 

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(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
 
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(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
 
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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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Posted by on July 14, 2021.

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