Neco 2018 chemistry theory & objectives answers

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*CHEMISTRY THEORY AND OBJECTIVE ANSWERS


*Note:* You are to answer 4 Questions only, in the Theory part


*GOOD LUCK* ......


*CHEMISTRY* ANSWERS

: 1a)
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
1aii)
i)Deuterium
ii)tritium'
1bi)

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.
2KMnO4(aq)+16HCl---->2MaCl2(aq)+8H2O(s)+5Cl2(aq)
1bii)
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
1ci)
GIVEN
P1=(745-13.5)mmHg =731.5mmHg
T1=(16+273)k=289k
P2=S.P=760mmHg
T2=S.T=273k
V1=40cm^3
using the general gas equation
P1V1/T1=P2V2/T2
V2=731.5*40*273/760*289
V2=36.4cm^3
the volume of the gas at S.T.P is 36.4cm^3
1cii)
i)Nature of reactions
ii)presence of a catalyst

ENGR NASER DAHER💪💪: 3ai)
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
3aii)
i)solubility
ii)boiling points
iii)densities
3aiii)

3bi)
catalyst are substance which alter the rate of a chemical reaction but not themselves used up in the process.
3bii)
i) they are proteinous in nature
ii)they alter the rate of a chemical reaction
iii)they are not use themselves up in the reaction
3ci)
The solution turn from blue to white as a magnesium displace copper from its salt
3cii)
Mg(aq)+CuSO4(aq)-----> MgSO4(aq)+ Cu(s)
3di)
Equation Reaction:
2Na(s)+O2(q)----->Na2O2(s)
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
=0.129*[(23*2)+(16*2)]
=0.129*78
=10g
3dii)
i)dissolving an acid on hydride in water
ii)combination of constituent element
3diii)
washing soda (NaCO3. 10H2O)
============================
 6ai)
NH4^+(aq)+OH^-(aq)+HCl(aq)---> NH4Cl(aq)+H2O(i)
6aii)
the student got the choice of indicator wrong
6aiii)
phenolphthalein is used when a strong base is present. aqueaous ammonia is a weak base
6b)
i)gluclose and fructose
ii)invertase
iii)delivery tube
iv)glucose
6ci)
white phosphorus and red phosphorus
6cii)
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)
6di)
GIVEN:
mass of P= 9g
molar mass of P =80g/mol
: Number of mole of P presnt =mass/molar mass
=9/80=0.1125moles
solubility =0.1125/60*100=1.875mol/dm^3
6dii)
C2H5OH(aq) +H2SO4(aq)----> C2H5HSO4(aq)+H2O(i)
C2H5HSO4(aq)---->C2H4(aq)+H2SO4(aq) ethene
6diii)
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.

4ai)
From the collision theory the rate of chemical reactions depend on the frequency of effective collisions cones that the result in reaction between reactant particles
4aii)
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
4aiii)
they are the most important processes for the commercial production of gasoline and diesel fuel
4bi)
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)
4bii)
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)
4ci)
CH(CH3)3,CH3CH2CH2CH3,CH3CH2CH2CH2OH/Increasing boiling points
4cii)
i)Bubbles formed at the bottom of liquid rise to the surface
ii)temperature remain steady
4ciii)
I. Addition of sodium chloride crystals raises the boiling point of water
II. Reduction in atmospheric pressure lowers the boiling point of water
4civ)
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


3(a) homologous series is a series of compound with the same Functional group and the similar chemical properties


*(3b)* Catalysis () is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst (), which is not consumed in the catalyzed reaction and can continue to act repeatedly.

(ii)  *properties of catalyst*👇

(I)  unchangeability of the catalyst

II)  small quantity of the catalyst

(III) initiation of the reaction

 3a1)
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

 3aii)
1)Each successive member differ in relative molecular mass by an increase of 14.

2)chemical properties of the member are similar but with a gradual variation  along the series.

3) each successive member in a series differ in molecule formula by the addition of a -CH2 -GROUP

 3bi) catalyst are substance which alter the rate of a chemical reaction but not themselves used up in the process

 3bii)
1) they are proteinous  in nature
2)they alter the rate of a chemical reaction
3)they are not use themselves up in the reaction


 1a, isotopy is a phenomenon whereby an atom of an element excite different mass number but have the same atomic number.

1b,  isomerism is existent of two or more compound (known as isomers) with the same molecular formulae but different molecular structure .


CHEMISTRY OBJ:
1-10: DADBCADBCA
11-20: DCDBDBEDDC
21-30: CBDEDBAAEA
31-40: ECCADAEDEB
41-50: EAADDACBBC
51-60: ADDDBACBEB





1a )
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

1aii )
i ) Deuterium
ii) tritium'

1bi) THE DIAGRAM

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 .
2KMnO 4( aq ) +16 HCl - -- - > 2MaCl 2( aq ) +8H 2O ( s ) +5Cl 2( aq )

1bii)
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

1ci )
GIVEN
P 1 = ( 745- 13. 5) mmHg = 731 .5mmHg
T 1 = ( 16+273 ) k = 289 k
P 2 = S . P = 760 mmHg
T 2 = S . T = 273 k
V 1 = 40cm ^ 3
using the general gas equation
P 1 V 1/ T 1= P 2 V 2/ T 2
V 2 = 731. 5* 40 * 273/ 760 * 289
V 2 = 36. 4cm ^ 3
the volume of the gas at S . T . P is 36. 4cm ^ 3

1cii )
i ) Nature of reactions
ii) presence of a catalyst
=======================================

6ai )
NH4^ +( aq ) + OH ^ -( aq ) +HCl ( aq ) -- - > NH4 Cl ( aq ) +H 2 O ( i )

6aii )
the student got the choice of indicator wrong

6aiii )
phenolphthalein is used when a strong base is present. aqueaous ammonia is a weak base

6b)
i ) gluclose and fructose
ii) invertase
iii ) delivery tube
iv ) glucose

6ci )
white phosphorus and red phosphorus

6cii )
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 )

6di )
GIVEN :
mass of P = 9g
molar mass of P = 80g/ mol
: Number of mole of P presnt = mass / molar mass
= 9/ 80 = 0. 1125 moles
solubility = 0. 1125 / 60* 100 = 1. 875mol / dm^ 3

6dii)
C 2 H 5OH ( aq ) +H 2SO 4( aq ) - -- -> C 2H 5 HSO4( aq ) +H 2O ( i )
C 2 H 5HSO 4( aq ) -- - -> C 2H 4( aq ) +H 2SO 4( aq ) ethene

6diii )
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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