2013 WAEC Chemistry OBJ and Theory Expo

Chemistry obj
1-10: ddacdccbcd
11-20: baddababab
21-30: abcdacbddc
31-40: abbbdacdba
41-50: bdaadaabcc


CHEMISTRY ANSWERZ

(1ai)Q and S
(1aii)Q and T, S and U
(1aiii) I. Q and S. II.by gaining
electron is U.
(1aiv) T
(1av) S and U .

(1bi) Electronegative ­ is the
tendency of an atom to gain
electron and become negatively
charge.
(1bii) it increases across the
period and decrease down
group.
(1biii) due to additional shell, it
increases down the group and
due to additional electron, it
decreases across the group
because the nuclei pull between
the proton inthe nucleus and
the valence increases.

(1c.)
(i)They have variable oxidation
state
(ii)They have the ability to form
coloured ion
(iii) They have the ability to
form complex ion.

(1di) 2KClO32KCl +3O2
(1dii) it serve as a catalyst and
makes the reaction to occur at
a lower temperature and at a
faster rate.
(1diii) molar mass of
KClO3=39+35.5+4 ­ 8=122.5g
molar mass of
KCl=39+35.5=74. ­ 5g. Mass of the
chloride produced (15*2*74.5)/
(2*122.5),=9.12 ­ 2g

(2a)Normal salt_ this is salt
formed when a strong base as a result of
complete neutralization.
(ii)acid salt- this is a formed when a strong
acid reacts with a weak base resulting in an
incomplete neutralization in which the salt
formed exhibit acidic properties.
(2aiii)H2SO(eg)
2NaOH~NO2SO4 2 H20 where
Na2SO4 is the normal salt
formed.H20SO4(A ­ q)
NaCH~NaHSO4 H2 O where
(NaHSO4)(aq).



(2b) the acidic base indicator-
This is reagent capable of giving
a colour change when the ph is
varied from 0-14 so as to
indicate the acidity or alkalinity
of the unknown solution
3a)
(i)the standard electrode
potentiaqlof the meteal ion on
the hydrogen scale is the
potential difference (in volts)
which exists between the metallic electrode and the
standard hydrogen elctrode
(ii)
-position of ions in the
electrochemical ­ ­ series
-concetration of ions
-nature of electrode
(iii)
-it allows ions to pasds from
one electrolytic solution to the
other


(3b)
if a copper plate is immersed in a solution of
copper(vi) tetraoxosulphate solution, Cu(2+)
ion acquires two electrons from the copper
plate to become deposited as neutral metallic
copper on the plate. a potential difference is
setup betwwen the copper metal and the
solution containing ions.
Cu(2+)(aq)+2e(-)=>Cu(s)

(3c)
Cu(2+)+ 2e(-)=>Cu
2*96500=64g
Q=it
Q=0.2*35*35*60
Q=420C
2*96500=64
420 columbs=64
mass:(64*420)/ (2*96500)
=0.139g