CHEMISTRY OBJ.
1DCDBCBDBCA
11DBAADCDBCB
21DBCBCCDBAD
31BACBACBCCD
41BDACABDABD

1ai)
an acid base indicator is a weak acid
or weak base that exhibits a colour
change as the concentration of
hydrogen (H^+) or hydroxide (H^-)
ions changes in an aqueous solution

1aii)
methyl-orange
1b)
i)oxidizing agent
ii)mixed anhydride

1c)
enthalpy of combustion is the heat
evolved when one mole of a
substance is completely burns in
oxygen gas under standard conditions

1cii)
enthapy of combustion is always
negetive since it involvs a rise in
temperature and heat of reactants is
greater than the heat of products

1d)
primary cell is a cell that cannot be re
charged while secondary cell is a cell
that can be recharged

1dii)
primary cell — daniell cell
secondary cell — lead accumulator

1e)
mole is the unit of measurement in
the International System of Units (SI)
for amount of substance. The unit is
defined as the amount of a chemical
substance which contains as many
representative particles, e.g., atoms,
molecules, ions, electrons, or photons,
as there are atoms in 12 grams of
carbon-12 (12C), the isotope of
carbon with relative atomic mass
1f)
n= V=40cm^3
c= 0.40moldm^3
n=cv/1000
0.40*40/1000 = 0.016mol

2a)
i)periodic law states that properties of
elements are the periodic function of
their atomic number
ii)periodic property of element is the
variation of the properties of element
in a regular pattern both down the
group and acrose the period

2aii)
i)ionization energy
ii)electron affinity
iii)electropositivity

2aiii)
ionization energy increase from left to
right acrose a period because the
nuclear charge increase progressively
while the screening effect remain
constant
-atomic reduis decreases from left to
right acrose the period because
nuclear charge effect out weighs
screening effect,which remains
constant because the number of shell
in a period is constant
-electron affinity increase from left to
right across a period because an
additional electron will experience a
greater repulsion than altraction from
the positively charged nucleus

2b)
the relative atomic mass of an
element is the mass of one atom of
the element compared with the mass
of an atom of the carbon -12 isotope
whos mass is exactly 12

2bci)
isotopy

2cii)
the isotopes have difference number
of neutron

2ciii)
R.A.M=(75/100*35)+(25/100*37)
=2634.25

2di)
I CO2 by downward delivery
II HCL by downward delivery
III H2 by upward delivery
2dii)
I because it is denser than air
II because it is denser than air
3ai)
Thermal cracking

3aii)
C4H8
3aiii)
(I) H H. H
| | |
H-C-C-C=C
| | | |
H H H H
and
(II) H H
| |
H-C-C=C-C-H
| | | |
H H H H
3aiv)
I-normal butene
II -But-2-ene
Ni
3av)
C4H8 +H2 ——-> C4H10
250c

3b)
method
– rub the fat on a blank white paper
– pour Sudan (III) dye over the paper
-wash the paper under tap
Observation
– rubbing the fat on the paper
produces a translucent color
-pouring sudan (III) will stain the
blot red
Conclusion
– fat is present because sudan (III)
can stain fat red

5ai) worm the unknown substance
with concentrated H2SO4 in a test
tube. if trioxonitrate(v) ion’s are/is
present, some trioxonitrate(v) acid will
be condensed as oily drops on the
upper part of the tube. On further
heating, the acid decomposes yielding
brown fums of NO2 gas.
5iia) Sodium chloride is used for
br /> =preserving food
=glazing pottery
5iib) Sodium trioxocarbonate(iv) is
used for br /> =standardizing acids in the laboratory
=the manufacture of glass

[5bi)
C(s) + O2(g) =====> Co2(g)
Co2(g) + C(s) =====> 2Co(g)
Fe2O3(s) + 3Co(g) =====> 2Fe(l) +
3Co2(g)
The limestone present decomposes as
follows br /> CaCo3(s) =====> CaO(s) + Co2(g)
Which is available to remove silicon
(iv) oxide impurity
SiO2(s) + CaO(s) =====> CaSiO3(s)

5bii) Faraday’s first law of electrolysis
states that, the mass (m) of an
element discharged during an
electrolysis is directly proportional to
the quantity of electricity (Q) passing
through it.

 264 total views,  1 views today