WAEC GCE Chemistry Questions and Answer – Nov/Dec 2017 Expo Runz
CHEMISTRY OBJ:
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4a)
i)the law of conversation of matter states matter can neither be created nor destroyed but can be changed from one form to another.
4aii)
i)gases move randomly in a straight line colliding with one another and to the volume of the container
ii)the volume occupied by the gas molecules are highly negligible when compared to the volume of the container
iii)the collision between gas molecules are perfectly elastic
4b)
i)producer gas(mixture of Co and N2)
ii)water gas(mixture of Co and H2)
iii)H2O(g) + C(s) —-> CO(g) + H2(g)
4ci)
i)benzene
ii)carbon(II)sulphate
iii)tarpentine
4cii)
There will be the formation of metanol.The reaction is endothermic reaction
4di)
CaCO3->CaO+CO2
4dii)
(I) p=120Nm^-2=118.81atm
V=0.25dm^3
R=8.314JKmol^-1
T=25C+273=298K
Using PV=nRT
=>n=PV/RT=(118.81*10^-5*0.25)/(8.314*298)
But n=mass/molar mass
=(29.7025*10^-5*)/(2477.572)
=>Mass of gaseous product=44.29.7025*10^-5/2477.572
=527*10^-6g
(II)
From the reaction, the moles of CaCo3 is the same as the mole of Co2; the number of moles of CaCo3
= 1.198*10^-7mole
But moles = mass/molar mass
Mass = moles × molar mass
Mass = 1.198×10^-7×100
= 119.8×10^-7
= 1.198×10^-5 moles
5a)
chlorine
/ammonia
/hydrogen-
chloride gas/carbon(II) oxide/sulphur(IV)oxide/nitrogen(IV) oxide
5ai)
because they are poisonous/
have offensive smell
/are dangerous to health
5aii)
1 Fused Calcium chloride is used in the manufacturing of plastics
2 Fused calcium chloride and the production of calcium salt. It is used in the production of concrete..
3 Fused Calcium chloride accelerates the curing (drying) speed of poured concrete.
2ai) it’s a group of atoms or type of bond possessed by certain organic compounds making them have some or similar chemical properties.
2aii)
I)Ester
II)Ethyl ethanorate
2bi)
I)Unsaturated hydrocarbon
II)Alkanol
III)Alkanoic Acid
2bii)
i)Acidified KMnO4 turns from purple to colourless
ii)A sweet smelling compound is produced
iii)Effervescence occurs with colourless odourless gas that turns lime water milky being evolved
2ci)
I)O
I)-1 and +1
2cii)
I)4H+ + No3— +3e— >NO + 2H2O
II)Mass/molar mass = It/πe— * 96500c
0.5/197 = 0.8*t/3*96500
t= 0.5*3*96500/197*0.8
t = 918.46s
2di)Group 2
II)X3N2
III)Beryllium
1a)
Standard hydrogen electrode This is an electrode system which is normally used as a reference electrode, it is formed when hydrogen gas at 25c and pressure of 1 atm is bubbled through onr molar (1M) of Hcl.
1b)
Metals are good reducing agent because the are electro donors (metal ionizes by loss of electron)
1c)
i)Diamond is used in jewelry because they resist chemical attack and high temperature.
ii)Diamond is used as abrassive because they are dense and hard.
iii)Diamond is a non conductor of electricity because they lack free valence electron
1di)
Chemical change: this is a change which is irreversible and new substances are formed. They are mainly in form of chemical reaction.
1dii)
example of chemical change.
I)rusting of iron
II)reaction of acid and Base to form salt and water
1e)
isotope: these are elements with the same atomic number but different mass number or atomic mass.
1f)
a weak acid is a substance which does not ionize or dissociate completely in solution. While a dilute acid is an acid with lower concentration, a dilute acid is formed when water is added to concentrated acid
1g)
PH: this is the negative logarithm to the base ten(10) of hydrogen concentration
Ph= -log10^H+
1h)
i)It causes formation of acid rain
ii)It causes photochemical smog and ozone layer depletion
1i)
Cl2 + Mgbr2 -> MgCl2 + Br2
1fi)
By simple diffusion
1fii)
Oxidation of the ethanol can be prevented by the removal of oxidizing agent such as Kmno4 or K2Cr2 or by the addition of lithium tetrahydrido aluminate(iii)
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