WAEC GCE Chemistry Obj And Essay/Theory Questions and Answer – NOV/DEC 2017 Expo Runz.

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OBJ 

1.CBDADCBABD 

11.BACCBBADCC

 21.DCACABABAA 

31.DDBDADBBDA 

41.BBACDBDCBA

CHEMISTRY ANSWERS VERIFIED!!!

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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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

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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

(4di)

Air the presence in or introduction into the air of a substance which has harmful or poisonous effects.

(4dii)

(i) Efficiency and Conservation

(ii) Carbon Capture

(4ei) 

(i) Production of hydrogen by electrolysis of water. 

(ii) Manufacture of heavy water

(iii) Electroplating

(4eii)

(i) Limestone

(ii) Coke

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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. 

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