Neco 2017 Chemistry Obj And £ssay Answers – May/June Expo @ blackloaded

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Chem obj

1-10ACBAEDCCAB

 11-20ECACDCADBC

 21-31ECBDDADACD

31-40CABEBBABEA

4159DDDBAABDEB

51-60CEEEECEEAA

1ai)-Boiling Point and Freezing Point.
-Surface Tension, Heat of Vaporization, and Vapor Pressure.

1aii)

1aiii)- Aluminium

1aiv)bauxite
CHEMISTRY SOLUTIONS BY DONIZZY

1ai)-Boiling Point and Freezing Point.
-Surface Tension, Heat of Vaporization, and Vapor Pressure.

1aii)

1aiii)- Aluminium

1aiv)bauxite

1bi)-A
-D
-
-
-

1bii) A standard solution is a solution containing a precisely known concentration of an element or a substance. A known weight of solute is dissolved to make a specific volume. It is prepared using a
standard subs as a primary
standard.

1biii)-A dilute solution contains a smaller amount of solute than does a concentrated solution
- A dilute solution contains more solvent than an equal volume of
concentrated solution does.

1ci)- monosaccharides 
-disaccharides 

1cii)

1ciii) A lighted wooden splint goes out in a
test tube of carbon dioxide but this happens with other gases, too. It is better to bubble the test gas through limewater - calcium hydroxide solution. Carbon dioxide turns limewater cloudy white.
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3ai)
i) Metals differ so widely in hardness, ductility (the potentiality of being drawn into wire), malleability, tensile strength, density, and melting point. 

ii) Mercury is liquid at room temperature and gallium melts on our hand while tungsten has a melting point of 3687K (3414 0C)

iii) Most metals are highly lustrous (they shine very brightly) and sonorous (they produce sound when struck)

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5a) Peroxide are oxides containing a higher proportion of oxygen than the ordinary oxides 

ii)-Sodium Peroxide Na2O2
-Hydogen Peroxide H2O2
-Barium Peroxide Ba2O
-Calcium Peroxide CaO2

Iii)
 II)The Ionic Polar Head of Soap Molecules that are responsible for it solubility 
III) In acidic Water it react with excess Hydogen ions to form unionized fatty Acids

iv) Biodegradibility of Soap Molecules means that Soap can easily be decomposed by bacteria into simple inorganic substances, so it does not cause Water Pollution
5ci) Boyle's law states that at constant temperature for a fixed mass, the absolute pressure and the volume of a gas are inversely proportional. The law can also be stated in a slightly different manner, that the product of absolute pressure and volume is always constant.
2ai )

oxidation is a process involving a loss of electron ( s ) , Reduction is a process in which an electronagetive element loses electron while an electropositive element gains electron .

2aii )

i ) nitrogen is colourless ,ordourless and testsless gas

ii) it is slightly soluble in water

2aiii )

x is ( NH2) 2 CO

y is H 20

2bi )

i ) element - chlorine

E/ configuration= 1s ^ 2, 2s ^ 2, 2p^ 6 3s ^ 2 , 3p^ 5 atomic number is 9

ii) NaOH= ( 23 * 1+16 * 1+1* 1)

= 23 +16+1 = 40g

avogrado 's constant = 6 .02 * 10^ 23

5g= 5/ 40* 6. 02* 10 ^ 23

= 6. 02* 10 ^ 23= 0 .753 * 10^ 23

= 7. 53* 10 ^ 22moles

iii ) fractional abundance

= 1/ 3 and 2 / 3

= 1/ 3 * 18 + 2/ 3 * 20

= 18 / 3+40/ 3 = 58/ 3

= 19 .33 g

2ci )

faraday 's second law of electrolysis states “ When the same quantity of electricity is passed through different electrolytes , the masses of different ions liberated at the electrodes are directly proportional to their chemical equivalents ( Equivalent weights ) .

2cii )

the single line represents one electron while double bonds represent two electrons

2ciii )

polymerization is any process in which relatively small molecules , called monomers, combine chemically to produce a very large chainlike or network molecule , called a polymer .

2civ )

i ) it is used for making wine ,beer , etc

ii) it is used as fuel

iii ) it is used as preservative and steriling liquids

iv ) it used for making anti -freeze reagents in automobile radiators

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6ai )

I ) solution A is starch solution, sample B is Iodine

II ) the colouration is formed due to the formation of an Iodine starch complex

III )

i ) Iodine is used in treatment of goitre

ii) Iodine is used in making dye for colour photography

6aii )

dalton 's law of partial pressure states that in a mixture of non -reacting gases , the total pressureexerted is equal to the sum of the partial pressuresof the individual gases.

6bi )

C - 4. 08/ 12 , H - 0. 68/ 1 , O - 5. 46/ 16

0. 34/ 0. 34, 0 .68 / 034, 0. 34/ 0 .34

1, 2, 1 .

The emperical formula is CH 2O

6bii)

( CH 2 O ) n = 60

((12 * 1) +( 1* 2) +( 16* 1 ))n = 60

( 12+2 +16) n = 60

30n / 30= 60 / 30

n = 2

( CH 2O ) 2 = C 2H 4O 2

the molecular formular is C 2H 202

6ci )

i ) exothermic reaction

ii) A is activation energy , B is DH ( Negative )

6cii )

i ) removeal of carbon ( iv ) oxide

ii) liquetying the air

6ciii )

vander waal forces

6di )

fats have higher melting point than oil because fats are more denser

6dii)

i ) it is poisonous

ii) it is 2,5 times denser than air

iii ) it is greenish - yellow gas with a choking smell

6diii )

Zn^ 2 + has comppletely filled d-orbitals and there are no vacant d-orbitals for the transition of electrons while Sc ^ 3+ has completely empty d-orbital and there are no electrons for d-d transition thus they are colourless
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