Chemistry JAMB, WAEC, NECO AND NABTEB Official Past Questions

Burette readings (initial and final) must be given to two decimal places. Volume of pipefte used must also be recored but no account of expeririental procedure is required. All calculations must be done in your answer book.

A is 0.100 mol dm\(^{-3}\) solution of an acid. B is a solution of KOH containing 2.8 g per 500 cm’\(^3\)

(a) Put A into the burette and titrate it against 20.0 cm\(^3\) or 25.0 cm\(^3\)  portions of B using methyl orange as an indicator. Repeat the titration to obtain consistent titres. Tabulate your readings and calculate the average volume of A used.

(b) From your results and the information provided above, calculate the:

(i) number of moles of acid in the average titre;

(i) number of moles of KOH in the volume of B pipetted;

(ii) mole ratio of acid to base in the reaction. [H = 1.00, O = 16.0, K = 39.0]

Credit will be given for strict adherence to the instructions, for observations precisely record and for accurate inferences. All tests, observations and inferences must be clearly entered in your answer book in ink, at the time they are made.

C is a mixture of two salts. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion drawn from the result of each fest

(a) Put all of C into a boiling tube and add about 5cm\(^3\) of distilled water. Stir thoroughly and filter. Keep both the residue and the filtrate.

(b) To about 2 cm\(^3\) of the filtrate, add few drops of Pb(NO\(_3\))\(_{(aq)}\). Boil the mixture and then allow to cool.

(c)(i) Put the residue in a test tube and add dilute HNO\(_{3}\). Shake the mixture and divide the solution into two portions

(ii) to the first portion from (c)(i), add NaOH\(_{(aq)}\) in drops acid then in excess.

(iii) To the second portion from (c)(ii), add aqueous ammonia in drops and then in excess

(a) A colourless gas P was given off when dilute tetraoxosulphate (VI) acid was added to zinc salt Q. On bubbling the gas through lime water, a white precipitate R was formed. Identify P, Q and R.

(b) Name a suitable apparatus that could be used to perform each of the following activities in the laboratory

(i) storage of dilute silver trioxonitrate (V):

(ii) heating copper metal;

(iii) separation of a mixture of water and Kerosene. Give one reason for each of your answers in (b)

(a)(i) Draw the energy profile diagram for the reaction; H\(_{2(g)}\) + I\(_{2(g)}\) \(\to\) 2Hl\(_{(g)}\); \(\Delta\)H = –13 KJ mol\(^{-1}\)

(ii) If the concentration of HI\(_{(g)}\) increases from 0.000 to 0.002 mol dm\(^{-3}\) in 80 seconds, what is the rate of t reaction?

(b)(i)Give one use of each of the following compounds: I. NaHCO\(_{3}\); II. CaSO\(_{4}\); III. CaCO\(_{3}\).

(ii) State a drying agent that can be used for each of the following gases: I. SO\(_{2}\); II. HCI; Ill. NH\(_{3}\)

(c)(i) Write an equation for the complete combustion of carbon in oxygen.

(ii) Calculate the number moles of carbon (IV) oxide produced from the complete combustion of 2.5 g of carbon. [ C = 12.0, O = 16]

(iii) Mention one use of I. carbon (II) oxide; II. carbon (IV) oxide.

(d) An industrial raw material has the following composition by mass:

Iron = 28.1%; Chlorine = 35.7%; Water cf crystallization = 36.2%.

Calculate the formula for the material. [H = 1.00, O = 16.0, CI = 35.5, Fe = 56.0]

(e) Give one example of a (i) metal that is liquid at room temperature,

(ii) non-metal that is liquid room temperature.
 

(a) A compound X reacts with excess HNO\(_{3(aq)}\) to give carbon (IV) oxide and another compound Y. A solution of Y reacts with NaOH\(_{(aq)}\) to form a white precipitate which is insoluble in excess NaOH\(_{(aq)}\). Identify X and Y.

(b) (i) Write a balanced equation to illustrate the reducing property of ammonia in its reaction with CuO.

(ii) Explain why it is not advisable to heat ammonium dioxonitrate (III) directly.

(iii) Give two uses nitrogen.

(c) Give the reason why (i) dilute H\(_{2}\)SO\(_{4}\) is not suitable for the preparation of CO\(_{2(g)}\) from CaCO\(_{3(s)}\) (ii) concentrated H\(_{2}\)SO\(_{4}\) cannot be used to dry ammonia gas.

(d) State two: (i) physical properties; (ii) chemical properties of metals.

(e) What is the oxidation number of: (i) chlorine in I. Cl\(_{2}\). II. ClO\(_{-(3)}\)

(ii) vanadium in V\(_{2}\)O\(_{5}\)

(f)(i) Explain the term half-life. (ii) Two radioactive elements, P and Q have half-life of 1200 seconds and 3600 seconds respectively.

I. Which of the elements is more stable? II. Give a reason for your answer.

(a)(i) What is a functional group?

(ii) State the functional group in each of the following compounds: I. CH\(_3\)CH\(_2\)CH(CH\(_3\))OH; II. CH\(_3\)CH\(_2\)CH\(_2\)COOH.

(b)(i) Complete the following equations:

(ii) Draw the structure(s) of the product(s) formed in (b)(i) above.

(c)(i).Write an equation for the prepzration of butan-2-ol from butene.

(d) (i) Give the reagents required for the following conversions to take place: I. CH\(_2\) = CH\(_2\) to CH\(_3\)CH\(_2\)OH; II. CH\(_3\)CH\(_2\)OH to CH\(_3\)COOH; Ill. CH\(_3\)COOH to CH\(_3\)COOCH\(_2\)CH\(_3\).

(e) Consider the following organic structure; CH\(_3\)OHCHCH = CHCOOH

(i) State what would be observed when the organic compound is treated with each of the following reagents: I. cold NaHCO\(_{3(aq)}\); II. hot solution of I\(_2\) in NaOH\(_{(aq)}\); Ill. bromine water.

(a)Define the term solubility.

(b) The table below gives the solubility of salt Z at various mperatures

(i) Plot a graph of solubility against temperature.

(ii) From the graph determine the solubility of salt Z at 35°C.

(iii) If 100cm\(^{-3}\) of the saturated solution is cooled from 55°C to 35°C, calculate the mass of salt Z that would crystallize out. [Molar mass of salt Z = 100 g]

(c)(i) Write a balanced equation to illustrate the reaction of AI\(_2\)O\(_3\) with dilute I. HCI; II. NaOH.

(ii) What is the name given to an oxide that exhibits both acidic and basic properties?

(iii) Give one metallic oxide which exhibite these properties.

(d)(i) Determine the oxidation number of: I. Al in [Al (H\(_2\)O)\(_6\)]\(^{3+}\); II. H in NaH.

(ii) Give the IUPAC name of each of the following substances; I. CuSO\(_4\).5H\(_2\)O; II. CaCO\(_3\); Ill. KMnO\(_4\).

The following table gives the atomic numbers of elements V, W, X, Y and Z.

(a)Which of the elements: (i) belong(s) to group 1?

(ii) is/are riotle gas(es)?

(iii) form(s) coloured compound(s)?

(iv) form(s) an anion?

(v) react(s) with water to liberate hydrogen?

(vi) react(s) with water to form alkaline solution?

(b) What is the:

(i) charge on the ion formed in

(a)(iv) above?

(ii) group of the element(s) in (a)(i) above?

(c)(i) Write the formula of the compound formed between element V and element W.

(ii) Sate the type of bond formed in (c)(i) above. Explain your answer.

(d)(i) What is a covalent compound?

(ii) Give two factors that influence covalent bonding.

(iii) State the type of bond that exists in each of the following substances: MgO, NH\(_3\) and Fe.

(iv) What are intermolecular forces?

(a)The table below gives the volume/pressure data for a particular sample of a gas-at a given temperature.

(i) Deduce a mathematical relationship between volume (V) and pressure (P).

(ii) Name law that can be deduced from the data.

(iii) Calculate the pressure of the gas when the volume is 3.20 dm\(^3\)

(b)(i) What is the role of a salt bridge in an electrochemical cell?

(ii) What type of ions must flow into the cathode? Give a reason for your answer.

(iii)A standard galvanic cell constructed with Ag\(^+_{(aq)}\) Ag\(_{(s)}\) and Zn\(^{2+}_{(aq)}\) couple is discharged until 3.3 g of Ag forms.

I. Write the overall cell reaction and standard cell potential?

II. How many moles of electrons flowed through the circuit during the discharge?

III. How many coulombs of charges flowed through the circuit?

Ag\(^+_{(aq)}\) + e\(^-\) \(\rightleftharpoons\) Ag\(_{(s)}\); E° = + 0.80V

Zn\(^{2+}_{(aq)}\) + 2\(^-\)  \(\rightleftharpoons\) Zn\(_{(s)}\), E° = – 0.76 V [Ag = 108]

(c)(i) Define each of the following terms: I. Activation energy; II. Exothermic reaction.

(ii) Give one example of an endothermic process.

(iii) What is the significance of activated complex in a chemical reaction?

Aluminium is extracted electrolysis from

Which of the following processes does not involve the use of limestone?

The following substances are ores of metals except

The reagent that can be used to distinguish ethene from ethyne is

The compound that makes palm wine taste sour after exposure to the air for few days is

When bromine is added to ethene at room temperature, the compound formed is

The following substances are examples of addition polymer except

Which of the following separation techniques would show that black ink is a mixture of chemical compounds?

Which of the following compounds would react with ethanoic acid to give a sweet smelling liquid?

Which of the following compounds determines the octane rating of petrol?

Consider the following electrochemical cell notation: M(s) / M2+ (aq)// H+ (aq)/ H2(g). The value of the electrode potential is positive when?

Which of the following metals could be used as sacrifical anode for preventing the corrosion of iron?