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Neco chemistry questions & answers 2023 (obj-essay) released.

See 2023 NECO Chemistry Answers & Questions Here.

The Neco chemistry answers for 2023 questions can now be seen here. The National Examination Council, NECO Chemistry SSCE paper is scheduled to be written on Monday, 24th July 2023 from 10:00 am to 1:00 pm.

This NECO Chemistry questions paper is for Papers III & II: Objective & Essay and will take a total of 3hrs to write.

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

NECO Chemistry Answers 2023.

1. a) (i) What is the structure of the atom as proposed by Rutherford? (ii) Distinguish between the atomic number and the mass number of an element. (iii) Explain briefly why the relative atomic mass of chlorine is not a whole number.

b) (i) What is meant by first ionization energy? (ii) List three properties of electrovalent compounds (iii) Consider the following pairs of elements: 9F and 17CL; 12Mg and 20Ca.

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

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

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?

Note:   There is nothing like Neco chemistry Expo online. Neco Ssce candidates are to desist from patronizing online fraudsters / vendors who says they can provide such services as they are not real.

Neco Chemistry Objective Questions 2023.

NOTE:  There is nothing like Neco chemistry expo online. Do not be deceived by fraudsters posing 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.

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NECO Chemistry Questions and Answers 2023/2024 (Essay and Objectives)

NECO Chemistry Questions and Answers 2023. I will be showing you past Chemistry objectives and theory repeated questions for free in this post. You will also understand how  NECO  Chemistry questions are set and how to answer them.

The National Examinations Council (NECO) is an examination body in Nigeria that conducts the Senior Secondary Certificate Examination and the General Certificate in Education in June/July and December/January respectively.

Table of Contents

NECO Chemistry Objectives and Essay Answers 2023 (Expo)

The 2023 NECO Chemistry expo will be posted here today 24th July during the NECO Chemistry examination. Keep checking and reloading this page for the answers.

NECO 2023 Chemistry Answers Loading.

OBJ Answers:

1-10: DEADADECAD

11-20: BAEDDBDBAE

21-30: CCDCABDDCD

31-40: EBEECEBCEE

41-50: BCCECDDADD

51-60: DABBDEAECA

————————————————————————————————————-

NECO Chemistry Questions and Answers For Practice

The following NECO Chemistry questions are questions to expect in the 2023 NECO examination.

1. The minimum amount of energy required for effective collisions between reacting particles is known A) Activation energy B) Bond energy C) Kinetic energy D) Potential energy

2. The bond formed between H2OH2O and H+H+ to form the hydroxonium H3O+H3O+ is A) Dative B) Covalent C) Electrovalent D) Ionic

3. An element XX forms the following oxides X2O,XOX2O,XO and XO2.XO2. This phenomenon illustrates the law of ________. A) Conservation of mass B) Definite proportion C) Mass action D) Multiple proportion

4.. How many moles of oxygen would contain 1.204×10241.204×1024 molecules? NB: Avogadro’s constant (NA) =6.02×1023=6.02×1023 A) 1 B) 2 C) 3 D) 4

See: NECO Timetable

5. Which of the following statements about solids is correct? A) Solid particles are less orderly than those of a liquid B) Solid have lower densities than liquids C) Solid particles have greater kinetic energies than those of liquids D) Solid particles cannot be easily compressed

6. Which of the following apparatus can be used to measure a specific volume of a liquid accurately? A) Beaker B) Conical flask C) Measuring cyclinder D) Pipette

7. The general gas equation PVT=KPVT=K is a combination of A) Boyle’s and Charles’ laws B) Boyle’s and Graham’s laws C) Charles’ and Graham’s laws D) Dalton’s and Graham’s laws

8. The spreading of the scent of a flower in a garden is an example of? A) Brownian motion B) Diffusion C) Osmosis D) Tynadal effect

9. Propane and carbon (IV) oxide diffuse at the same rate because [H = 1.00, C = 12.0, O = 16.0] Options A) They are both gases B) Their molecules contain carbon C) They have the same relative molecular mass D) Both are denser than air

1O. The energy which accompanies the addition of an electron to an isolated gaseous atom is A) Atomization B) Electronegativity C) Electron affinity D) Ionization

11. A sample of hard water contains some calcium sulphate and calcium hydrogen carbonate. The total hardness may therefore be removed by A. boiling the water B. adding excess calcium hydroxide C. adding a calculated amount of calcium hydroxide D. adding sodium carbonate E. adding magnesium hydroxide

12. During the electrolysis of copper II sulphate between platinum electrodes, if litmus solution is added to the anode compartment, A. the litmus turns blue but no gas is evolved B. the litmus turns blue and oxygen is evolved C. the litmus turns blue and hydrogen is evolved D. the litmus turns red and oxygen is evolved E. the litmus turns red and then becomes colourless

13. The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as; A. saponification B. dehydration C. esterification D. hydrolysis E. hydration

14. The IUPAC names of the compounds CH3COOH and CH2=CH2 are respectively; A. acetic acid and ethane B. ethanoic acid and ethene C. methanoic acid and ethylene D. ethanol and ethene E. acetic acid and ethylene

15. If 30cm3 of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm3 of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively? A. 9.3 sec B. 14 sec C. 21 sec D. 28 sec E. 30.3 sec

16. When heat is absorbed during a chemical reaction, the reaction is said to be A. thermodynamic B. exothermic C. isothermal D. endothermic E. thermostatic

17. When large hydrocarbon molecules are heated at high temperature in the presence of a catalyst to give smaller molecules, the process is known as A. disintegration B. polymerization C. cracking D. degradation E. distillation

18. The pH of four solutions W, X, Y, Z are 4, 6, 8, 10 respectively, therefore A. none of these solutions is acidic B. the pH of Y is made more acidic by addition of distilled water C. Z is the most acidic solution D. W is the most acidic solution E. X is neutral

19. When each of the nitrates of Potassium, Magnesium and iron is heated, A. all the nitrates decompose to their oxides B. the nitrate of magnesium gives the nitrite and oxygen C. the nitrates of iron magnesium and iron give the oxides D. the nitrate of iron gives the nitrite and oxygen E. the nitrate of the magnesium is not decomposed

2O. Which of the following metals cannot replace hydrogen from water or steam? A. Sodium B. Magnesium C. Iron D. Calcium E. Copper

21. small quantity of solid ammonium chloride (NH4Cl) was heated gently in a test tube, the solid gradually disappears to produce two gases. Later, a white cloudy deposit was observed on the cooler part of the test tube. The ammonium chloride is said to have undergone A. distillation B. sublimation C. precipitation D. evaporation E. decomposition

22. Elements P, Q, R, S have 6, 11, 15, 17 electrons respectively, therefore, A. P will form an electrovalent bond with R B. Q will form a covalent bond with S C. R will form an electrovalent bond with S D. Q will form an electrovalent bond with S E. Q will form a covalent bond with R

23. An element X forms the following compounds with chlorine; XCl4, XCl3, XCl2. This illustrates the A. law of multiple proportions B. law of chemical proportions C. law of simple proportions D. law of conservation of mass E. law of definite proportions

24. The oxidation state of chlorine in potassium chlorate is A. +1 B. +2 C. +3 D. +5 E. +7

25. 10 When air which contains the gases Oxygen, nitrogen, carbondioxide, water vapour and the rare gases, is passed through alkaline pyrogallol and then over quicklime, the only gases left are; A. nitrogen and carbondioxide B. the rare gases C. nitrogen and oxygen D. nitrogen and the rare gases E. nitrogen, carbondioxide and the rare

26. Which of the following statements is NOT correct? A. The average kinetic energy of a gas is directly proportional to its temperature B. At constant tempearture, the volume of a gas increases as the pressure increases C. The pressure of a gas is inversely proportional to its volume D. The temperature of a gas is directly proportional to its volume E. The collisions of molecules with each other are inelastic

27. Zinc Oxide is a A. Basic Oxide B. Acidic Oxide C. Amphoteric Oxide D. Neutral Oxide E. Reactive Oxide

28. When sodium chloride and metallic sodium are each dissolved in water A. both processes are exothermic B. both processes are endothermic C. the dissolution of metallic sodium is endothermic D. the dissolution of metallic sodium is exothermic E. the dissolution of sodium chloride is explosive

29. The periodic classification of elements is an arrangement of the elements in order of their A. Atomic Weights B. Isotopic Weights C. Molecular Weights D. Atomic Numbers E. Atomic Masses

3O. In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm3 of 1.25 molar sulphuric acid? A. 5cm3 B. 10cm3 C. 20cm3 D. 25cm3 E. 50cm3

Recommended: How to check NECO Result

NECO Chemistry Questions And Answers 2023 (Paper 2)

Don’t worry about these NECO Chemistry Questions And Answers 2023. All you need to do is to keep on refreshing this page for the 2023 NECO Chemistry Questions And Answers for this year. It will be posted here in few minutes.

Tips on How to Pass 2023 NECO Chemistry Examinations

The following guidelines will help you pass the 2023 NECO Chemistry examination with flying colours.

Have a Target and Work Towards Actualizing it 

You have decided to pass NECO Chemistry 2023 and I am sure of that. Now, the next thing you should do is set targets.

You have told yourself, “I will score A in NECO Chemistry 2023”, that’s not all. You need to plan on how to make it happen. Create a timetable and master plan to achieve your goals.

 Get the Recommended Textbook on Chemistry for 2023 NECO Examination

Normally, NECO recommends books for the examination. But apart from NECO Literature in English where certain novels are compulsory, you are free to use any good Chemistry textbook to prepare for NECO 2023 exam.

Some textbooks are more difficult to understand. If you have any topic you are finding difficult to understand, then get a textbook that will simplify the topics and make life better for you.

 Do not Skip Chemistry Examples and Exercise you Will Come Across While Reading: 

Many candidates are fond of skipping exercises and even examples while studying textbooks. In fact, we like notebooks so much that we could ask, “can I read my notebook and pass NECO Chemistry 2023?” Don’t be scared of attempting exercises in Biology. Face the challenges.

If you have any questions about the  NECO Chemistry Questions and Answers 2023 , kindly drop your question in the comment box.

Last Updated on July 25, 2023 by Admin

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122 thoughts on “NECO Chemistry Questions and Answers 2023/2024 (Essay and Objectives)”

Please when will the answer come up

I just need questions for the two

I am really greatfull for the coperation you showed to us most especially me if not for you guys thisneco would have been trouble so sincear thank you

WHERE IS THE ANSWER FOR THE OBJ QUESTIONS THAT IS UP THERE

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Genuine Exam Past Questions and Answers Online Bookshop – PDF and MS Word Download

NECO Chemistry Past Questions Download -Theory, Objective, Practical

Are you writing the National Examination Council NECO internal/external exam, if yes you need the NECO Chemistry Past Questions

we at stcharlesedu.com has compiled a good number of NECO Chemistry Past Questions Chemistry Paper 2 – Theory/Essay Questions Chemistry Paper 3 – Objective Test Questions

Our research has confirm that candidate that uses National Examination Council Chemistry past questions to prepare for NECO is ten times better than those who do not.

Table of Contents

• 1.1 Chemistry Paper 3 (III) Objective Test Questions
• 2.1 Chemistry Paper 2 (II) Essay Questions
• 3 Free Download Chemistry NECO Past Questions PDF
• 4 How to Get National Examination Council NECO Chemistry Past Questions

NECO Chemistry Objective Questions

Find out the correct option for each question and shade in pencil on your answer sheet, the answer space which bears the same letter as the option you have chosen. Give only one answer to each question and erase completely any answer you wish to change. Do all rough work on the question paper.

Chemistry Paper 3 (III) Objective Test Questions

Each question is followed by five options lettered A – E.

1. The raw material used in cement production is A. calcium trioxocarbonate(IV). B. hydrochloric acid. C. sodium trioxocarbonate(IV). D. tetraoxosulphate(VI) acid. E. trioxocarbonate(IV) acid.

2. When bromine atom changes to bromide ion, it A. is neutralized. B. is oxidised. C. is reduced. D. loses a proton. E. loses an electron.

3. The following are non electrolytes except A. benzene. B. ethanol. C. petrol. D. sodium ethanoate. E. sucrose solution.

4. The best way to dispose chemical waste is by A. burning. B. burying. C. decomposing. D. recycling. E. refrigerating.

5.Which of the following forms an anion by accepting an electron? A. Chlorine B. Hydrogen C. Magnesium D. Potassium E. Sodium

6. Calculate the relative molecular mas of sodium hydrogen tetraoxosulphate (Vl). (Na=23, H=l, S=32, O=16). A. 130 B. 120 C. 66 D. 64 E. 46

7. The measure of the average kinetic energy of the molecules of a gas is its A. density. B. mass. C. pressure. D. temperature. E. volume.

8. The brown ring test is for identification of A. nitrogen (II) oxide. B. nitrogen (III) oxide. C. nitrogen (IY) oxide. D. tetraoxosulphate (VI) ion. E. trioxonitrate (V) ion.

9. Ethanol is used in alcohol thermometer because of its A. high boiling point. B. high freezing point. C. high melting point. D. low freezing point. E. high volatility.

10. The gas used in fire extinguisher is A. argon. B. caibon(IV) oxide. C. nitrogen. D. oxygen. E. water vapour.

11. The chemical process that uses steam, coke and water for the production of hydrogen is known as A. bosch. B. contact C. frasch. D. haber. E. solvay.

12.A salt which loses its water of crystallization on exposure to the atmosphere is A. anhydrous. B. deliquescent C. effervescent D. efflorescent. E. fluorescent.

13. Calculate the concentration in gdm -3 of a solution containing 0.01 moldm -3 of K 2 CO 3 (K= 39, C = 12, O = 16).

A. 0.47 B. 0.67 C. 1.38 D. 1.40 E. 2.38

18. Hypochlorous acid is used as a bleaching agent because it/it’s A. a reducing agent B. a strong acid. C. a weak acid. D. an oxidizing agent. E. forms chlorine in water.

19. A base that is soluble in water is referred to as A. acid. B. alkali. C. crystal. D. hydride. E. salt

20.The components of universal indicator can be separated by A.chromatography. B.crystallization. C.evaporation. D.filtration. E.sublimation.

21.Potassium is difficult to extract because it A. evaporates very fast. B. has low density. C. is deliquescent. D. is highly reactive. E. is soft.

NECO Chemistry Theory Questions

Do not open this paper until you are told to do so. While waiting, read the following carefully. Write your Name and Examination Number in the spaces provided at the top right-hand comer of the booklet This paper consists of six questions. Answer four questions only. Write your answer in blue or black ink in your answer booklet Only Scientific or English names are acceptable. All questions carry equal marks. Use of mobile phone is not allowed. Use of scientific calculator is allowed.

Chemistry Paper 2 (II) Essay Questions

Answer any four questions from this paper.

1(a) i. Mention three examples of heavy chemicals. (3marks) ii. 3Cu (s) + 8 HNO 3(aq) -> 3Cu(NO 3 ) 2(aq) + 4H 2 O (l) + 2NO (g) From the equation above which of the substances is: I. An oxidizing agent II. A reducing agent (2marks) iii. What is the oxidation state of copper in CuCl? (l mark)

(b) i. State three factors that determine preferential discharge of ions. (3marks) ii. Mention two factors that affect the standard electrode potential. (2marks)

(c) Zinc tetraoxosulphate(VI) solution was electrolysed with 0.6 ampere for 1300 seconds, depositing 0.288 g of zinc at the cathode. Calculate the number of: i. Moles of zinc deposited ii. Coulombs of electricity required (1 Faraday = 96,500C, Zn = 65) (6marks)

(d) i. What is reforming? (2marks) ii. State two reactions that occur during reforming. (2marks) iii. Give two conditions necessary for rusting to occur. (2marks) iv. Mention two ways in which rusting can be prevented. (2marks)

2(a) i. Name two natural processes that involve the use of carbon(IV) oxide in the atmosphere. (2marks) ii. Mention two sources of chemical wastes. (2marks) iii. How many unpaired electrons are present in the d-orbital of Fe3+? (lmark)

(b) i. List three types of iron. (3marks) ii. Mention two adverse effects of chemistry. (2marks)

Chemistry Theory Questions 3 – 5 omitted – removed

6(a) i. Describe one chemical test to distinguish between ethene and ethyne. (3marks) ii. Write an equation for the reaction of ethene with hydrogen. (3 marks)

(b) i. State the reasons why it is not safe for a human to stay in a closed garage with a car engine running for a long time. (3marks) ii. What is the relative atomic mass of an element? (2marks) iii. Calculate the volume of oxygen liberated if 5.6 dm -3 of SO 3 was heated in excess oxygen. (molar volume of a gas = 22.4 dm 3 ) (5 marks)

(c) i. What is the importance of NaCl in the production of soap? (3marks) ii. Mention two advantages of soapless detergent? (2marks)

(d) i. State three properties of enzymes. (3 marks) ii. What is the effect of heat on protein? (l mark) iii. What name is given to the process in (d)ii? (l mark)

Free Download Chemistry NECO Past Questions PDF

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June/July NECO Chemistry Questions 2024 Free Answers (Essay & Obj) 100% Verified Solution

NECO 2024 Chemistry essay and OBJ answers is now available. If you are writhing this subject, Here is 2024 NECO Chemistry Questions June/July verified solution. Thd news reaching us is that the exam will take place on 12th of July, 2024. The National Examinations Council (NECO) is a Nigerian examination body responsible for conducting and administering national examinations at the secondary school level. NECO plays a crucial role in assessing and certifying students’ academic achievements across various subjects.

The NECO Chemistry exam will assess students’ understanding of chemical concepts and principles. It will evaluate their ability to apply this knowledge to real-world scenarios and problem-solving situations involving chemicals.

We know how hard it is understand the chemistry concept. You do not need to worry as we are going to make everything easy for you, including the answers

This is to bring to the notice of all students writing, especially the those in science that chemistry expo answers is ready with us. We ensured that the answers are in line with the marking scheme.

Please note that our chemistry is not free. Do not expect the questions and answers posted here. To get the solution, Join us on WhatsApp and pay #1000.

NECO chemistry June/July expo questions and answers will be uploaded in this page. Here, you will see all the necessary guide and the best way to tackle the problem.

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Also Read: NECO Timetable

Is NECO chemistry Questions 2024 Answers Out?

Yes, we wish to alert all student that the much awaited National examination board chemistry theory and Obj is out. We have long concluded the solving and and released to our VIP group members.

NECO has scheduled the Chemistry Objective and Essay exams (Papers III & II) for Friday, 12th July, 2024, from 10:00 am to 1:00 pm. The combined duration for both papers is three hours.

We advise that all student for this subject should prepare effectively for the exams, ensure you review all your notes thoroughly and practice with past questions to familiarize yourself with the exam format.

Go to Edureport Chemistry Page To See All The Question Papers Now.

NECO Chemistry Essay Answers

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The Chemistry 2024 exam theory (essay) answers will be uploaded for free here. All you need to do now is to keep refreshing this page, and invite others to do the same.

*NECO 2024 CHEMISTRY THEORY ANSWERS*

`ANSWER FOUR(4) QUESTIONS ONLY“`

(1a) (i) Hydrogen gas is colorless and odorless. (ii) Hydrogen is highly flammable, which means it can easily catch fire when exposed to a flame or spark. (iii) Hydrogen gas has low density, making it lighter than air.

(1b) (I) Group 17 (halogens) (II) lodine (III) lodine

(1ci) I. Calcium (Ca²⁺) II. Magnesium (Mg²⁺)

(1cii) I. lon exchange method II. Lime-soda method

(1di) (I) Methyl orange is used in the titration of a strong acid with a strong base. (II) Phenolphthalein is used in the titration of a strong base with a strong acid.

(1dii) (I) Hydrated salt: Copper(II) sulfate pentahydrate (CuSO₄.5H₂O) (II) Acidic salt: Ammonium chloride (NH₄Cl) (III) Basic salt: Sodium carbonate (Na₂CO₃)

(1ei) 2-methylbutane –> pentane –> 2,2-dimethylpropane

(1eii) (I) 1-bromo-3-methylbutane (II) 2-methylpentane

(1eiii) Benzene is used as a starting material in the production of various important chemicals such as ethylbenzene, cumene, cyclohexane, and nitrobenzene.

(1eiv) Saponification is a process in which ester molecules are hydrolyzed in the presence of a strong base (such as sodium hydroxide or potassium hydroxide) to form alcohol and the salt of the carboxylic acid.

(1f) Given, Vapour density = 77

molecular mass of XCl₄ = Molecular mass = Vapour density x 2 = 77 x 2 = 154

Molecular mass of XCl₄ = X + 4(Atomic mass of Cl) 154 = X + 4(35.5) X = 154 – 142 X = 12

:. The relative atomic mass of X is 12. ===================================

(2ai) A molar solution (M) is a solution that contains one mole of solute (dissolved substance) per liter (dm³) of solution.

(2aii) Convert volume from cm³ to dm³: 250cm³=0.250dm³

Number of moles of Na₂CO₃ = Concentration(mol/dm³) × Volume (dm³) = 0.10mol/dm³ x 0.25 dm³ = 0.025mol

Mass of Na₂CO₃ = Number of moles x Molar mass(g/mol) = 0.025 mol x 106 g/mol = 2.65 g

(2bi) (i) K > 1: Indicates that, at equilibrium, the concentration of the products is greater than the concentration of the reactants. The reaction favors the formation of products. (ii) K < 1:Indicates that, at equilibrium, the concentration of the reactants is greater than the concentration of the products. The reaction favors the formation of reactants. (iii) K = 1: Indicates that, at equilibrium, the concentrations of reactants and products are equal. Neither the reactants nor the products are favored.

(2bii) (i) Temperature: Increasing temperature can shift the equilibrium position depending on whether the reaction is endothermic or exothermic. (ii) Pressure: For reactions involving gases, changing the pressure can affect the equilibrium position. (iii) Concentration: Altering the concentration of reactants or products can shift the equilibrium.

(2ci) (I) Strong acids completely dissociate in water, while weak acids partially dissociate (II) Strong acids have a high tendency to donate protons, whereas weak acids have a lower tendency

(2cii) (I) Covalent compounds have low melting and boiling points (II) They are generally insoluble in water (III) Covalent compounds tend to be soft and brittle.

(2di) Diagram

(2dii) The monosaccharides contained in sucrose are glucose and fructose.

(2diii) (I) Temperature: High temperatures can cause proteins to unfold and lose their functional shape. (II) pH Levels: Extreme pH levels (either too acidic or too basic) can disrupt the hydrogen and ionic bonds that maintain a protein’s structure. ===================================

(3ai) (i) Stage 1: Production of sulfur dioxide: S(s) + O₂(g) ==> SO₂(g)

(ii) Stage 2: Conversion of sulfur dioxide to sulfur trioxide: 2SO₂(g) + O₂(g) <==> 2SO₃(g)

(iii) Stage 3: Absorption of sulfur trioxide in water to form tetraoxosulphate (VI) acid: SO₃(g) + H₂O(l) ==> H₂SO₄(l)

(3aii) (i) Temperature: Increasing the temperature can increase the rate of reaction by providing more kinetic energy to the molecules involved. However, this may not always favor the equilibrium position. (ii) Pressure: For gaseous reactions, increasing the pressure can shift the equilibrium towards the side with fewer moles of gas molecules. (iii) Concentration: Higher concentrations of reactants can increase the rate of reaction, but it may not affect the position of equilibrium.

(3aiii) (i) Relative positions of ions in the electrochemical series. (ii) Concentration of ions in the electrolyte solution. (iii) Nature of the electrodes.

(3b) Molar mass of MgSO₄= Mg + S +4 * O Molar mass of MgSO₄= 24 + 32 + (4*16) = 24+32+64= 120g/mol

The molar concentration in mol/dm³= 0.75mol/dm³

Given the mass concentration of the hydrated salt= 184.5g/dm³

Mass concentration=molar concentration * molar mass of MgSO₄⋅XH₂O 184.5 = 0.75 * molar mass of MgSO₄⋅XH₂O Molar mass of MgSO₄⋅XH₂O= 184.5/0.75 = 246g/mol

Molar mass of MgSO₄⋅XH₂O= molar mass of MgSO₄ + X * molar mass of H₂O

246 = 120 + X * (2*1+16) 246 = 120 + X * 18 246 = 120 + 18X X = (246 – 120)/18 X = 126/18 X = 7

(3ci) Reduction refers to the process where an atom, ion, or molecule gains electrons, leading to a decrease in its oxidation number.

(3cii) The oxidizing agent in the reaction is Br₂

(3ciii) (I) Contain carbon-hydrogen bonds. (II) Often have covalent bonding. (III) Can be highly complex in structure.

(3civ) (I) Plants (e.g., olive oil, sunflower oil) (II);Animals (e.g., butter, lard) ===================================

(4ai) Allotropy is the existence of two or more different forms of the same element in the same physical state.

(4aii) Carbon

(4aiii) (I) It is used in carbonated beverages to provide fizziness. (II) It is used in fire extinguishers as it is denser than air and can displace oxygen, thereby suffocating the fire.

(4bii) Calcium reacts with oxygen to form calcium oxide (CaO): 2Ca + O₂ ==> 2CaO

Molar mass of calcium: 40g/mol Molar mass of oxygen: 16g/mol

Number of moles of Ca = 4.8g/40g/mol = 0.12mol

Number of moles of O₂ = 0.12mol (since it’s a 1:1 ratio)

Mass of oxygen required = 0.12mol x 16g/mol = 1.92g

(4ci) (I) X is Iron(III) oxide (Fe₃O₄) and Y is Hydrogen gas (H₂) (II) Equation: 3Fe + 4H₂O ==> Fe₃O₄ + 4H₂

(4cii) Yellow color (lead iodide, PbI₂)

(4ciii) Diagram

(4di) Nitrogen prepared from air is often denser than pure nitrogen because it contains impurities, mainly argon and small amounts of other gases. These impurities increase the overall mass per unit volume of the gas mixture compared to pure nitrogen, making it denser. When nitrogen is extracted from the air, it is typically around 99.9% pure, but that 0.1% of impurities, such as argon, oxygen, and trace gases, can still affect its density.

(4dii) Percentage composition of sodium in NaNO₃: Percentage of an element = (Atomic mass of the element * Number of atoms of the element/molecular mass of the compound) * 100

Molar mass of NaNO₃: Na: 23g/mol N: 14g/mol O: 16g/mol * 3 = 48g/mol

= 23 + 14 + 48 = 85 g/mol

Percentage of Na: (Mass of Na / Molar mass of NaNO₃) x 100% = (23/85) * 100 = 0.2706 x 100 = 27.06%

(4diii) (I) Ammonia (NH₃): Heavy chemical (II) Drugs: Fine chemicals (III) Sodium hydroxide (NaOH): Heavy chemical ===================================

(5ai) (I) A is NH₃ (Ammonia) and B is HCl (Hydrochloric acid). (II) Decomposition reaction

(5aii) (I) All members of a homologous series have the same functional group, which gives them similar chemical properties. (II) There is a gradual change in physical properties (such as boiling point, melting point, and solubility) as the molecular mass increases.

(5aiii) (I) lonic bond (II) Covalent bond (III) Metallic bond

(5bi) (I) Anhydrous Copper(II) Sulfate (CuSO₄) (II) Cobalt(II) Chloride Paper (CoCl₂)

(5bii) (I) Ensure the burette is calibrated correctly (II) Use a white tile or paper to read the meniscus clearly (III) Take readings with the eye level at the meniscus

(5ci) (I) Atomic radius: -Across the Period: Atomic radius decreases from left to right across a period. This is because the number of protons in the nucleus increases, pulling the electrons closer to the nucleus due to stronger electrostatic attraction. -Down the Group: Atomic radius increases down a group. This is because additional electron shells are added, making the atom larger despite the increase in nuclear charge.

(II) Ionization energy: -Across the Period: Ionization energy increases from left to right across a period. This is due to the increasing nuclear charge, which holds the electrons more tightly and requires more energy to remove one. -Down the Group: Ionization energy decreases down a group. As the atomic radius increases, the outer electrons are farther from the nucleus and are less strongly attracted, making them easier to remove.

(5cii) (I) Potassium (K): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ (II) Magnesium (Mg): 1s² 2s² 2p⁶ 3s² (III) Oxygen (O): 1s² 2s² 2p⁴

(5di) (I) H⁺ (hydronium ion) (II) H₃O⁺ (hydronium ion)

(5dii) A physical change is a change in which the substance undergoes a change in state or form, but its chemical composition remains the same. Examples include melting, freezing, boiling, condensation, and sublimation. ===================================

(6ai) Ethene: C₂H₄ has a double bond between two carbon atoms. Ethyne: C₂H₂ has a triple bond between two carbon atoms.

(6aii) Polyacetylene

(6aiii) Structure of Polyethylene: (-CH=CH-)n

(6bi) (I) Fehling’s solution added to reducing sugar: Precipitate formation (red precipitate indicates presence of reducing sugar) (II) Millon’s reagent added to protein: White precipitate formation (indicating presence of protein) (III) Sodium metal dropped into ethanol: Vigorous reaction, flame, and formation of sodium ethoxide

(6bii) Solubility of KCIO (potassium hypochlorite): Molar mass of KCIO₃: 39 + 35.5 + (3*16) = 122.5g/mol

Convert mass of KCIO₃ to moles = 4.9/122.5 = 0.04mol

Volume of water = 20cm³ = 0.02dm³

Solubility S in mol/dm³ = moles of KCIO₃/Volume of water in dm³ = 0.04/0.02 Solubility= 2.0mol/dm³

(6ci) (I) It is a colorless liquid at room temperature. (II) It has a characteristic odor. (III) It is miscible with water in all proportions.

(6cii) Equations for preparation of ethanol from ethene: (I) C₂H₄ + H₂O ==> C₂H₅OH (hydration reaction) (II) C₂H₄ + H₂SO₄ ==> C₂H₅HSO₄ (sulfonation reaction) (III) C₂H₅HSO₄ + H₂O ==> C₂H₅OH + H₂SO₄ (hydrolysis reaction)

(6di) (I) It is used in the manufacture of glass. (II) It is used in water softening and as a cleaning agent.

(6dii) (I) They often exhibit variable oxidation states. (II) They form colored compounds and ions. (III) They have catalytic properties due to their ability to adopt multiple oxidation states and their surface structures. ===================================

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Tips For passing NECO Chemistry exam

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