NECO CHEMISTRY PRACTICAL ANSWERS ARE AVAILABLE

NECO CHEMISTRY PRACTICAL SOLUTION
titre:
Vol of acid used in cube : 28.00³
Initial reading : 0.00
Final reading: 28.00³
2nd titre:
Vol of acid used in cube : 30.00³
Initial reading : 0.00
Final reading: 30.00³
3rd titre:
Vol of acid used in cube : 26.00³
Initial reading : 0.00
Final reading: 26.00³
Average vol of acid used=28.00³+30.
00+26.00 =84
84/3= 28.00
.: the average titre value is 28.00
*note your school will give a value. Your value
should not be more or less than +/- 0.2 to
what is being given* ++++++++++++++++++
+++++++
++++++++++
(1a)
Titre value: Under 1:
20.70, 0.00, 20.70
Under2:
20.70, 0.00, 20.70
Under3:
20.70, 0.00, 20.70 Under Initial reading:
0.00, 0.00, 20.70, 20.70
Under volume of Acid used:
20.70, 20.70, 20.70
Average value= (20.70+20.70=
20.70)/3 VA=(63.10)/3= 20.70cm^3
(1bi)
Given CA=?
CB=0.10mol^-3
VA=20.70 cm^3
VB=25.0CM^3 NA=1
NB=2
H2C2O4+ 2NAOH=> Na2C2O4+
2H20
CAVA/CBVB= NA/NB
(CA*20.70)/0.10 *25.00cm^3= 1/2
CA= (1*0.10*25.0)/2*20.70
CA2.50/41.40
=0.603mol dm^-3
(1bii)
CA=mass concentration/molar mass
H2C2O4=((2*4)+(2*c)+(4*0))
gmol
((2*1)+(2*2)+(4*10))g/mol
2+24+48g/mol
=72g/mol 0.0603= mass contration/72
=4.348g/dm^3
(1biii)
mass of pure= 4.35gdm^-3
mass of impure=6.30g/dm^-3
% purity= mass of pure/ mass of impure * 100%
=4.35/6.30 * 100%
=4.35/6.30 %
% purity= 69.01%
(1biv)
methyl orange is not used because it is a
titration between
weak acid and strong base, the
end point will not coincide with
the PH which the indicator
exhibits of colour change
========================= ===========
(2ai)
OBservation: salt C dissolves in
distilled water
inference: Salt C is a soluble salt
(2bi) observation:
Rusty brown precipitate is
formed in excess
interference:
Fe(3+) is present
(2bii) OBSERVATION: formation of
blood-red precipitate
Inference: Fe(3+) is confirmed
(2ci)
Observation: formation of white
precipitate which dissolves on heating
Inference: SO3(2-), SO4(2-) are
likely to present
(2cii)
Observation:
A pungent gas is evolved, the gas turns moist
blue litmus paper to
red and turns acidified K2Cr2O7
from orange to green colour
Inference:
An acidic gas is evolved i.e SO2
gas is evolved from SO3(2-) (2ciii)
Observation: white precipitate is
formed
Inference: SO4(2-), SO3(2-) are
likely present
(2iv) observation: the white
precipitate is soluble in dil HCL
Inference: SO3(2-) present.
=========================
===============
(3ai) using lime water
(3aii) by determining its boiling
point and melting point
(3aiii)by direct evaporation
(3aiv)by sieving
(3bi)addition of water, to be followed by
filtration and then
crystallization
(3bii)in evaporation, the salt are
always stable to heat.