Sunday, 17 April 2016

Waec chemistry Essay And OBJ

CHEM-OBJ
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41abdbbbaabb[4/18, 2:45 PM] Nos-Tech: (4ai)
calcium chloride, CaCl2

(4aii)
to the unknown ssubstance in a gas jar, add small quantity of lime water. if the gas is carbon(iv)oxide, it turns lime water milky while carbon (ii) oxide has no effect

(4bi)
oxygen is releasedf abundantly from air and nitrogen is produced by the reaction of potassium trioxonitrate(v) with concentrated hydrochloric acid

(4bii)
oxygen gas rekindle a lighted splint while nitrogen does not

(4ci)
Bauxite is preferred because it is readily available in the earth crust

(4cii)
-trioxosilicate(iii)
-carbon(iv)oxide

(4ciii)
-it helps to purify the bauxite

(4civ)
it is difficult to extract aluminium by chemical reduction of aluminium oxide in amphoteric

(4cv)
AL2O3+NaOH=>Na2O + Al+ H20
[4/18, 2:46 PM] Nos-Tech: Chem-Theory-Answers

typing no3 keep refreshing

==================================

1a)

nucleons is the collective name for two important sub-atomic particles:neutrons and protons

1b)

Graham's law of diffusion states that at a constant temperature and presure,the rate of diffusion of a gas is inversely proportional to the square root of it density

1c)

because when aluminum is exposed to moist air,a thin continuous coating of aluminum oxide is formed, which prevents futher attack of the aluminium by atmospheric oxygen and water or steam under normal conditions

1d)

i) electron - affinity

ii) electron - negativity

iii) ionization - energy

1e)

i) the molecule of real gases occupies space and there are forces of the attraction between them

ii) real gases do liquefy when their temperature droops.

1f)

i)used in seperation of different component of crude oil.

ii)it is used for separating acetonic from water

iii) it is used for obtaining different gases from air for industrial use.

1g)

i)concentration of ions in electrolyte

ii)the nature of the electrode

iii)the position of ions in the electrochemical series

1h)

i)substitution reaction

ii)addition reaction

1i)

i)carbon dioxide

ii)water vapour

iii) carbon monoxide

1j)

i)centrifugation

ii)sieving

iii)evaporation to dryness

==================================

2a)

i) isotopy

ii) they have the same number of proton (atomic number) but different mass number

iii) oxygen,carbon

iv)1s^2,2s^2,2p^6,3s^2,3p^5

2bi)

PHYSICAL PROPERTIES

METAL

i) high melting and boiling point

ii) they are good conductor of heat and electricity

NON-MATEL

i)they have lower melting and boiling point

ii)they are poor conductors of heat and electricity.



CHEMICAL PROPERTIES

METAL

i) they form basic and ampheric oxides

ii)the react by electron lose or donation of electron

NON-METAL

i)the form acidic oxides

ii)the react by sharing and accepting electrons

2bii)

i) Al2 O3(Aluminum oxide)

ii) sodium hydride (NaH)

iii)zinc trioxocarbonate(iv)ZnCo3

iv)silicon tetrachloride (SiCl4)

2ci)

i) variable oxidation states

ii) complex ion formation

iii) they possess strong metallic bonding

2cii)

1s^2,2s^2, 2p^6, 3s^2, 3p^6, 3d^10, 4s^2

2ciii)

Zinc is not considered as a typical transition element bacause it has only one oxidation state of +2, it metallic ion are not coloured and it is not used as a catalyst.

2d)

Na2Co3 + MgCl2 ---->2NaCl + MgCo3

1mole 1mole 2mole 1mole

molar mass of Na2 Co3 = 2 * 23 + 12 * 1 + 16 * 3 = 46+12+48 = 106g

==================================

5ai)

Na2S2O3 ===>2 + 2x + 6 = 0

2x = 6 - 2 = 4

X = 4/2

X = 2

The oxidation number of sulphur is 2



5aii)

Rhombic&monoclinic



5aiii)

- Both are tetravalent

- both are allotrope of carbon



5bi)

CO2&Chloroflorocarbon



5bii)

There is increase in sun radiation reaching the earths surface ie Global warming



5biii)

ThunderStorm



5iv)

I2KNo3. -------->2KNO3 + O2

2AgNo3 --------->. 2Ag + 2No



5ci)

Calcium chloride in a solution can give rise to crystal using filteration&evaporation to dryness. The sol is filtered into filtrate&residue b4 evaporation to dryness takes place.



5cii)

- Because of presence of hydrogen bonding in NH3

- Because Iodine as higher molecular mass than chlorine



5di)

Mol of Nacl = Mass / MM

= 5.85/ 58.01

= 0.1mol

From the equation

2mol of Nacl gives 2mol of HCL, 0.1mol of Nacl gives 0.1mol of Hcl

Vol of Hcl = 0.1 x 22.4 = 2.24mol/dm^3

==================================
[4/18, 2:47 PM] Nos-Tech: 3ai)
structral isomerism is the existance of two or more compounds ( known as isomers) with the same molecular formula but different molecular structures
3ai)
i) tertiary alkanol
ii) secondary alkanol 
iii) primary alkanol
3bi)
i) 2[CH3 CH2 COOH ] 2K(s)---->
ii) [CH3 CH2 COO ] K + H2

i) 2[CH3 CH2 COOH ] +2 K(s) ------> 2[ CH3 CH2 COO ] K + H2
ii) CH3 CH2 COOH + C4 H9OH
HEAT---->CH3 CH2 COO C4 H9 + H20
H2SO4
iii)CH3 CH2 CH2 CH20H + H^+
KMnO4------> CH3 CH2 CH2 CH2 - 0H
EXCESS
3bii)
i) potassium ethanoate,hydrogen
ii) butyl propanoate and water
iii) enthanal
3c)
the percentage composition of the hydrocarbon
= 100
H + C = 100
14.3 + C =100
C= 100 - 14.3
C= 85.7%

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Nonso Michael

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I am Nonso Michael. I am a trained mobile phone software engineer, I enjoy helping people fix software problems in their phone.email me nostech4nija at gmail dot com

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