The NECO chemistry answers 2020 obj essay is out for those searching for neco chemistry expo 2020.

The Neco chemistry answers 2020 questions here were obatined from past www neco question and answer com and it’s for the sole aim of revision. The National Examination Council, NECO Chemistry SSCE paper is scheduled to be written on Wednesday, 18th November, 2020 by 10:00 am.

This Neco chemistry question paper is for Papers III & II: Objective & Essay and will take a total of 3hrs to write.

Here, we will be posting out the neco chemistry questions for candidates that will participate in the examination. Note that below is the questions from Neco chemistry past questions and answers that we feel are likely questions for SSCE preparation.

NECO Chemistry Answers 2020.

 

1. (a) State
(i) Pauli’s Exclusion principle;
(ii) Hund’s rule of maximum multiplicity.  [4 marks]

(b)  Write the electronic configuration of each of the following  ions of copper:

I.  Cu+;
II.  Cu2+.
[29Cu]

(ii)   Give the number of unpaired electrons in each of the ions in
1(b) (i) above.

(iii)  State the type of reaction represented by the following equation:
2Cu+(aq)  →   Cu2+(aq) + Cu(s)

(iv)   Write the formula of one compound of Cu+.    [6 marks]

(c) (i)  Name the type of radiation that will

I.    penetrate lead block;
II.   be stopped by thin paper.

(ii) Give the charge on each of the radiations mentioned in
1(c) (i) above.

(iii) What term is used to describe each of the following nuclear processes?

I.   Combination of two lighter nuclei to form a heavy nucleus
II.  Splitting of a heavy nucleus into two or more lighter nuclei
III. Time required for one-half of the atoms of a radioactive  substance to decay   [7marks]

(d) Arrange the following ions in order of increasing size.  Give a reason for your answer in each case.

I.   Li+, K+ , Na+;
II.  O2-,  F-,  N3-.  [4 marks]

(e) Determine the percentage composition of phosphorus and oxygen in phosphorus (V) oxide.
[P  =  31, O  =  16]   [4 marks]

2. a) (i) Define nuclear fission.
(ii) Consider the equilibrium reaction represented by the following equation: A2(g) + 3B2(g)                    2AB3(g); H = + kJmol-1. Explain briefly the effect of each of the following changes on the equilibrium composition:

  • increase in concentration of B;
  • decrease in pressure of the system;
  • addition of catalyst.

b) The lattice energies of three sodium halides are as follows:

Compound

NaF

NaBr

NaI

 Lattice energy/kJmol-1 890 719 670

Explain briefly the trend.

c) State the property exhibited by nitrogen (IV) oxide in each of the following reactions:
(i) 4Cu + 2NO2        4CuO + N2;
(ii) H2O+ 2NO2       HNO3 + HNO2.

3. a) (i) Define saturated solution.
(ii) Distinguish between dative bond and covalent bond.
(iii) Explain why sugar and common salt do not conduct electricity in the solid state.
(iii) State the type of intermolecular forces present in: hydrogen fluoride; argon.
(iv) Consider the compounds with the following structures:
S – H —-N and 0 – H —–N
In which of the compounds is the hydrogen bond stronger? Give reason for your answer.

(b) (i) State Dalton’s Law of Partial Pressure.
(ii) If 200cm3 of carbon(IV) oxide were collected over water at 18°C and 700 mmHg, determine the volume of the dry gas at s.t.p.
[ standard vapour pressure of water at 18°C = 15 mmHg]

4. a) (i) Define ionic bond.
(ii) What type of bond(s) exist(s) in: magnesium oxide; ammonium ion?

b) (i) Determine the oxidation number of sulphur in Na2S2O3.
(ii) State Faraday’s first law.
(iii) Give one example each of: acid salt; base salt.

c) (i) Name the type of energy change that occurs in each of the following processes;
I2(s)     ———>     I2(g);
C1(g) + e-      ——>     C1-(g).
(ii) State the effect of each of the following aqueous solutions on litmus paper:
Na2SO4(aq);
AlC13(aq)
(iii) Define the term efflorescence.
(iv) Give two uses of activated charcoal.

d) (i) State one use of each of the following processes in the chemical industry: hydrogenation of vegetable oil; cracking; esterification.
(ii) Calculate the amount of silver deposited in moles when 10920 coulombs of electricity is passed through a solution of a silver salt.
[Faraday constant = 96500 C mol-1]

5. a) (i) Define in terms of electron transfer
I.  oxidizing agent;
II.  reducing agent.
(ii) Write a balanced equation to show that carbon is a reducing agent.
(iii) State the change in oxidation number of the specie that reacted with carbon in 5 (a)(ii).

b) A gas X has a vapour density of 32. It reacts with sodium hydroxide solution to form salt and water only.  It decolourizes acidified potassium tetraoxomanganate (VII) solution and reacts with H2S to form sulphur.  Using the information provided:
identify gas X; state two properties exhibited by X; give two uses of X.

c) Consider the following substances:
(1) sodium;
(2) lead (II) iodide;
(3) hydrogen;
(4) magnesium;
(5) oxygen.
Which of the substances
(i) conducts electricity?
(ii) is produced at the cathode during electrolysis of H2SO4(aq)?
(iii) corresponds to the molecular formula AB2  ?
(iv) is an alkaline earth metal?

d) (i) Define the term salt.
(ii) Mention two types of salt.
(iii) Give an example of each of the salts mentioned in 5(d)(ii) above.

e) In a neutralization reaction, dilute tetraoxosulphate (VI) acid completely reacted with sodium hydroxide solution.
(i) Write a balanced equation for the reaction.
(ii) How many moles of sodium hydroxide would be required for the complete neutralization of 0.50 moles of  tetraoxosulphate (VI) acid?

6. a) (i) What are acidic oxides?
(ii) Give one example of each of the following oxides:
I. acidic oxide;
II. basic oxide;
(III) amphoteric oxide;
(III) neutral oxide. [5 marks]

(b) (i) Define each of the following terms:
(I) Heat of combustion;
(II) Heat of neutralization.

(ii) Write an equation to illustrate each of the terms in 7(b)(i) above.

(iii) Given that the standard heat of combustion of butane (C4H10) is + 5877 kJmol-1, calculate the heat of combustion of 14.5 g butane.

[H  =  1, C  =  12]    [10 marks]

(c) (i) Name two allotropes of sulphur.
(ii) State one difference between the two allotropes.     [3 marks]

(d) (i) Give two characteristics of noble gases.
(ii) State one use each of
(I) He;
(II)  Ar.   [4 marks]

(e)  State what is observed on warming ammonium trioxonitrate (V) with sodiumhydroxide. [2 marks]

Neco Chemistry Objective Questions  2020.

1.

NOTE: That there is nothing like Neco chemistry expo online. Do not be deceived by fraudsters posing with fake NECO chemistry answers on the internet.

 

13.  At a particular temperature and pressure, 15.0 g of CO2 occupy 7.16 liters.  What is the volume of 12.0 g of CH4 at the same temperature and pressure?
A.

14.

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