2014/15 NABTEB GCE (Private) Nov/Dec CHEMISTRY Answers Available Here.

- December 04, 2014
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NABTEB CHEMISTRY OBJ:
1-10: CBCACBDCCD
11-20: BACBCDBAAA
21-30: CDABACBCDB
31-40: BADCCACDDC
41-50: ABDCBCBCBB
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(1a)
(i)Law of definite proportion states that a chemical compound always contains exactly the same proportion of elements by mass.
(ii)7.10g of A gives 5.62g of metal
6.04g of B gives 4.84g of metal
Total mass =10.46g
Proportion of A=(7.10/5.62)*10.46
=13.21
Proportion of A=(6.04/4.84)*10.46
=13.05
(1b)
(i)Electrovalent bond
(ii)Covalent bond
(iii) (bi) CE
(bii) E2
(1ci)
The bond in b(i) is formed by transferring electron S from C , i.e one electron from C to E to form CE while the bond in b(ii) is formed by sharing of electrons both in the outermost shell of E to E2
(1cii)
-Their atoms are held together by weak intermolecular forces
-They do not conduct electricity
-They have low boiling and melting point
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(2ai)
Graham's law of diffusion states that the rate of diffusion of gases is inversely proportional to the square roots of their vapour densities at constant temperature and pressure
(2aii)
Relative molecular mass(M) is two times the vapour density
M=2*V.D
(2aiii)
Rate of diffusion of oxygen(Ro)=100/30 =3.3cm^3S^-1
Rso2=rate of diffusion of SO2
Molecular mass of SO2=32+(16*2)
Molecular mass of oxygen=16*2=32
R is proportional to 1/sqroot(M)
R1/R2=sqroot(M2/M1)
3.3/R2=sqroot(64/32), 3.3/R2=sqroot(2)
R2=3.3/sqroot(2)=2.33cm^3/s
R2=Rso2=V/t
2.33=150/t
t=150/2.33=64.4s
(2b)
(i)The PH of a solution is scale showing the degree of acidity and alkalinity of a substance
(ii)
I D
II C,D,F
III E
IV A,E
v B
(2c)
(i)Sodium trioxocarbonate(iv)decahydrate
Na2CO3.10H2O
(ii)Potyassium hydroxide(KOH)
(iii)Copper(II)oxide(CuO)
======================================p
(3a)
(i)
I-K2CO3+HCl->KCl+H20+CO2
II-COOH-COOH+H2SO4-.H2O(l)+CO2+CO+H2SO4
(ii)This is because carbon(II)oxide is a poisonous gas
(3bi)Carbonhydrate is a large group of organic compounds containing carbon,hydrogen and oxygen 1:2:1
(3bii)CH2O
(3biii)Preparation of ethanol from a named cereal crops is called fermentation.The starch granules are extracted from a starch food by pressure cooking to a certain temperature and pressure.Sucrose is a mixture of glucose and fructose.The enzymes such as invertase is added to sucrose to form glucose
C12H22O11+H2O + invertase->2C6H12O6
The glucose formed is then broken into ethanol and carbon(3biv)oxide.The enzyme that is added to glucose to convert it to ethanol and carbon(iv)oxide is zymase.The ethanol can be collected
C6H12O6+Zymase->2C2H5OH+2CO2
(3c)
(i)The molecule of an element is the smallest particle in a chemical element or compound that has the chemical properties of that element
(ii)Sodium tetraoxosulphate(vi) (Na2SO4)
Sodium trioxosulphate(v) Na2SO3
(iii)The atomic mass is the number of neucleons in the nucleus of atom while relative atomic mass is the weighted average mass of an element to one-twelveth the mass of carbon-12
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(4a)
(i)Electrolyte is a substance which has the ability to conduct electricity in liquid or molten form.Examples are Urine,Brine while Non-electrolyte is a substance that do not allow or conduct electricity in molten or liquid form.Examples are alcohol
(ii)-Metallic conductor are solid while electrolyte are liquid or molten substance
-Metallic conductor contains electron while electrolyte are mobile electrons
(4b) I-Faraday's second law states that masses of different substance deposited or liberated by the same quantity of elctricity are directly proportional to the chemical equivalents of the substance
II-Faraday's first law of electrolysis
III-The time is 11.5seconds
(4c)
(i)The shape is linear
(ii)This is because of mass of element deposited is directly proportional to time
===COMPLETED===
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