NECO 2014/2015 Chemistry Objective & Essay Questions And Answers

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NECO 2014/2015 Chemistry Objective & Essay Questions And Answers
  • CHEMISTRY OBJECTIVE
    Verify Chemistry OBJ
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    11. EEDAEADDBB
    21. AACBDEABCC
    31. DBCCAAAACA
    41. EACEEEEAAA
    51. EEBCABBACA


    CHEMISTRY THEORY ANSWER

    1ai) Atomicity is the number of atoms in a molecule of an element
    1aii) Mass number of an element is the sum of the proton number and
    the neutron number
    1aiii) Isotopy is the existence of atom of the same element that have
    the same atomic number but different mass number
    1bi) The reaction is a displacement reaction because Zinc will displaced hydrogen from hydrochloric acid because it is above hydrogen in the activity series.
    There is an effervescence & hydrogen gas is given off the gas is collected over water because it is insoluble in water
    Zn + Hcl ----------- Zncl2 + H20
    1bii)
    * It is used in filling ballons because it has a low density
    * it is used in hardening Fat and oils in the manufacture of margine
    and other solid fats
    * it is used in the manufacture of ammonia in the harber process
    1c)
    Molar mass of HNO3 = 1 + 14 + (16)3 = 63g/mol% of oxygen = (16)3/63 x 100% = 76.19%

    1d)* copper
    * iron
    * Tin
    * Aluminium

    1e)* Sodiumtetrahy-droxozinate
    (ii) --------- Na2Zn(OH)4
    * sodiumoxonitrate
    (iii) --------- NaNo2

    1eii)* Used in soap making
    * used to soften hard water
    * used as fertilizer
    * sodium chloride is used as preservative for meat and fish

    2a) cassiterite
    2aii) Sn02 + 2c(s) -------------> Sn(s) + 2CO(g)
    2aiii)[b]
    [b]*
    Ethanoic acid from vinegars
    * Tartaric acid from grapes
    * Lactic acid from milk
    * Amino acid from protein

    2bi)* used in making cooking utensils
    * used in making alloy
    * used in making overhead electric cable

    2bii)* Increasing the concentration
    * Increasing the temperature of a system
    * Increasing the surface area of magnesium
    2biii) Mg + 2HCL -------------> Mgcl + H2

    2c)* Downward delivery or upward displacement of air
    * hydrogen chloride gas
    * ammonia gas
    * solubility

    2di) The heat involved when one mole of substance is burned completely in
    oxygen under standard condition
    (2dii) DG = DH - TDS
    = -710 - (300 x 0.15) = -755kg/mol

    (2diii)* It alters the rate of chemical reactions
    * it is specific in action
    * it cannot start a reactions
    * it has no effect on the equilibrium position of a reversible reaction

    3a)* Double decomposition reaction
    * Redox reaction
    * Displacement reaction
    3bi). (I) R - OH (ii) R - COOH (iii) R - C=O-R
    Where R= alkyl group = CnH2n+1

    3bii) CnH2n-2
    3biii)* All members can be prepared by the same general method
    * They have similar chemical properties
    * They share same general molecular formula
    * Each successive member differ by -CH2

    3ci)* Hydrogentetraoxosulphate(vi)acid [ H2So4 ]
    * Hydrogentrioxonitrate(v)acid [ HNO3 ]
    * Hydrochloric acid [ HCL ]

    3cii)* Ethanol ,
    * propan-2-ol
    3d) 19A »»» 1s2, 2s2, 2p6, 3s2, 3p6, 4s1
    9B »»» 1s2, 2s2, 2p5

    3dii) Electovalent bond
    3diii) * Soluble in water
    * Insolube in organic solvent
    * Conduct electricity in aqueous
    3e) diff in solubility from 100oc to 15oc = 39.8 - 35.9= 3.9g
    I.E solute deposited on cooling, on cooling from 100oc to 15oc,
    Mass involved at 100oc= 39.8g + 1000g of water = 1039.8g
    Mass involved at 15oc= 35.9g + 1000g of water = 1035.9g
    Ie 1039.8g of saturated solution deposited 3.9g of solute.
    Ie 80g of saturated solution deposite -------- 3.9 x 80/1039.8= 0.30g of water

    4a) Allotropy is the existence in the same physical state of two or
    more structural forms of the same element
    4aii) * Rhombic sulphur
    * Monoclinic sulphur
    * Amorphous sulphur
    * Plastic sulphur
    4b) * cracking process
    * C8H18 - octane
    * It reduce knocking

    4c) * Addition polymerization
    * Condensation polymerization
    4cii) hardness of water ia a suitation whereby water does not lather
    easily with soap

    4di) octane salting is a figure indicating the antiknock properties of
    a fuel based on a comparison with a mixture of isoctane & heptane

    4dii) Cracking: this is whereby complex molecule are broken down into
    simpler molecule. While,
    Reforming: is the process used to convest molecule having low octane
    rating into high octane liquid product

    4diii)
    Cu2+ + 2e- ----------> Cu
    2F ------------> 1 mole
    2 x 96500c ----------> 1 mole
    482.5c -------------> M/64
    2 x 96500 x M/64=482.5
    M= 0.16g

    4e) * chlorofluoro carbon
    * Carbon(ii)oxide
    * Sulphur(iv)oxide

    5ai)* An aerosol is a colloid of fine solid particles or liquid droplets in air or another gas
    * An emulsion is a collided solution of liquid in liquid

    5aii) i) Haze.
    (ii) Milk

    5aiii) Harber process
    * Hydrogenation process

    5bi) Fractional distillation
    5bii) High inflammable
    * insoluble in water
    * Good organic solvent

    5c) used in manufacture of HCL
    * for water purification
    * dyeing industry
    * manufacture of organic substance

    5cii) SOLID: molecule are fixed and tightly packed
    * It has a definite shape
    * they are compacted together LIQUID: molecule are loose
    * it takes shape of the container
    * it moves freely 5d) HCL + NAOH ——–> NACL + H20 Ca=? , Va=20.30cm ie 20.30 x 10^-3dm3,
    Vb= 25 x 10^-3 , Cb=0.1
    Ca = 0.1 x 25×10^-3/20.30 x 10^-3
    Ca = 0.123mol/dm3

    6a) standard heat of naturalization is the heat change when one mole of hydrogen ion from acid react with one mole of hydroxide ion from an alkaline to form one mole of water under standard conditions

    6aii) Conc H2S04 , conc HCL , Aluminium tetraoxosulphate(vi)

    6aiii) Temperature , Amount of solute in solvent

    6b) As fire extinguisher
    * in photosynthesis process
    * in the solvay process
    * As coolant in nuclear reactions


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