NECO Chemistry Obj and Essay Answer – 2018 June/July Expo

NECO Chemistry Obj and Theory/Essay and Answer – June/July 2018 Expo Runz

Answer 4 Question From This Section  Only
I. Isotopy is a phenomenon whereby an atom of an element excite different mass number but have the same atomic number.
II. Isomerism is existent of two or more compound (known as isomers) with the same molecular formulae but different molecular structure
(i) Deuterium
(ii) Tritium
Bottomed flask and set up the apparatus as shown. Add conc HCl gradual into the flask through the thistle funnel pass the gas produced through water and concentrated tetraoxosulphate (iv) and collect it by downward delivery.
(i) It is use as a bleaching agent
(ii) It is use as disinfectant in the treatment of water
(iii)it is use as an oxidizing agent
P1=(745-13.5)mmHg =731.5mmHg
using the general gas equation
The volume of the gas at S.T.P is 36.4cm^3
(i) Nature of reactions
(ii) Presence of a catalyst
A homologous series is a family of organic compound which follows a regular structural pattern in which each successive member differ in its molecular formula. By-CH2-GROUP
(i) Solubility
(ii) Boiling points
(iii) Densities
A catalyst is a substance which alter the rate of a chemical reaction without itself being used up in the process.
(i) They are proteinous in nature 
(ii) They alter the rate of a chemical reaction
(iii) They remain unchanged in the reaction
The solution turn from blue to white as a magnesium displace copper from its salt
Mg(aq)+CuSO4(aq)—–> MgSO4(aq)+ Cu(s)
Equation Reaction:
Number of moles of soduim =mass/molar mass =5.95/23=0.2587moles
Reactive ratio of sodium to its oxide is 2:1
Therefore number of moles of Na2O2=0.2587/2=0.129moles
Mass of oxide 
(i) Dissolving an acid anhydride in water
(ii) Combination of constituent element
Washing soda (NaCO3. 10H2O)
From the collision theory the rate of chemical reactions depend on the frequency of effective colparticles cones that the result in reaction between reactant particle
cracking means breaking down or decomposition of a compound by the action of heat alone. while Reforming is the breaking down of a compound by the use of a catalyst
they are the most important processes for the commercial production of gasoline and diesel fuel
I. Limestone: the limestone decomposes when heated to yield carbon(iv)oxide which is a major reactant
II. Ammonia: The ammonia reacts with the carbon(iv)oxide ammonium hydrogen trioxocarbonate(iv)
I. B belong to the class of compound called carbohydrates
II. C is ethanol [C2H5OH] , D is ethylethanoate [CH3COOC2H5]
III. Functional group is -OH
IV. CH3COOH(aq)ethanoic acid + C2H5OH(aq)c —–>conc H2SO4(catalyst) —–> CH3COOC2H5(i) + H2O(i)
CH(CH3)3,CH3CH2CH2CH3,CH3CH2CH2CH2OH/Increasing boiling points
i)Bubbles formed at the bottom of liquid rise to the surface 
ii)temperature remain steady
I. Addition of sodium chloride crystals raises the boiling point of water
II. Reduction in atmospheric pressure lowers the boiling point of water
I. N2O has oxidation state of +1 for Nitrogen
II. NO has oxidation state of +2 for Nitrogen
III. NO2 has Oxidation state of +4 For Nitrogen
NH4^+(aq)+OH^-(aq)+HCl(aq)—> NH4Cl(aq)+H2O(l)
The student got the choice of indicator wrong
Phenolphthalein is used when a strong base is present. Aqueaous ammonia is a weak base
(i) Gluclose and fructose
(ii) Invertase
(iii) Delivery tube
(iv) Glucose
White phosphorus and red phosphorus
I. Has no effect of red litmus paper
II. changes damp blue litmus paper pink
III. Reacts directly with alkali to yield a trioxocarbonate(iv)
mass of P= 9g
molar mass of P =80g/mol
: Number of mole of P presnt =mass/molar mass
solubility =0.1125/60*100=1.875mol/dm^3
C2H5OH(aq) +H2SO4(aq)—-> C2H5HSO4(aq)+H2O(i)
C2H5HSO4(aq)—->C2H4(aq)+H2SO4(aq) ethene
Bromine Exists as liquid at room temperature because there is decrease in votality down the group of the halogens due to increasing strength of the van der waal’s force.
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