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3446

(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.
 

View Answer & Discuss WAEC 2011
3447

 (a) i) Give the name and nature of the radiations that are emitted during radioactivity.

ii) State two differences between chemical reaction and nuclear reaction.

iii) Balance the following nuclear reactions and identify X and Y.

I. \(^{212}_{84} PO\) \(\to\) \(^{208}_{82} Pb\) + X 

II \(^{137}_{55}Cs\) \(\to\) \(^{137}_{55}Ba\) + Y 

(b) The electron configuration of an element X is: 1s\(^2\) 2s\(^2\) 2p\(^6\) 3s\(^2\) 3p\(^5\)

(i) Deduce the atomic number of X.

(ii) To what group does X belong?

(iii) Give two properties of the group to which the element X belong.

(iv) Identify element X by name.

(v) Write a balanced equation to represent the reaction between the element X and hot concentrated NaOH.

 

(c)(i) Explain why: I. graphite is used as a lubricant;  II. diamond is used as an industrial cutting tool.

(ii) Write an equation to represent the reaction between aqueous HCI and NH\(_3\) solution.

(iii) Name the type of reaction represented by the equation.

View Answer & Discuss WAEC 2010
3448

(a) (i) Define saturated solution.

(ii) Tha solubility of KNO\(_3\) at 20°C was 3.00 mol dm\(^{-3}\) If 67.0g of KNO\(_3\) was added to 250 cm\(^{-3}\) of water and stirred at 20°C, determine whether the solution formed was saturated or not at that temperature. [ KNO\(_3\) = 101.0 ]

(b) (i) Distinguish between dative bond and covalent bond.

(ii) Explain why sugar and common salt do not conduct electricity in the solid state.

(iii) State the type of intermolecular forces present in: I. hydrogen fluoride; II argon.

(iv) Consider the compounds with the following structures. S - H ---- N and O - H ---- N In which of the compounds is the hydrogen bend stronger? Give reason for your answer.

(c) (i) State Dalton's Law of Partial Pressure.

(ii) If 200cm 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]

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3449

(a) (i) Define a base according to Arrhenius concept.

(ii) Give one example of an Arrhenius base.

(iii) Identify each of the following substances in aqueous solutions as strong electrolyte, non-electrolyte or weak electrolyte.

I. C\(_{12}\)H\(_{22}\)O\(_{11}\)  II. NH\(_3\) Ill. NaOH

(iv) Write a balanced equation to represent the reaction between CH\(_3\)COOH and KOH.

 

(b) Calculate the volume of 0.500 mol dm\(^{-3}\) HCI required to neutralize 20.00 cm\(^3\) of 0.300 mol dm\(^{-3}\) NaOH.

(c) Give the IUPAC name of each of the following salts: (ii) NaOCI; (iii) Mg(HCO\(_3\))\(_2\).

(d)(i) Define the term standard solution.

(ii) Consider the following compounds: NaOH and Na\(_2\)CO\(_3\). Which of the compounds is suitable for the preparation of a standard alkaline solution? Give reason for your answer

(iii) Fe completely reacted with dilute HCI.

I. Write an equation for the reaction

II. If 3.08g of Fe completely reacted with 50.0 cm\(^3\) of 2.20 mol dm\(^{-3}\) HCI, calculate the relative atomic mass of the metal.

View Answer & Discuss WAEC 2010
3450

(a)(i) Give the two reasons why soda lime is used instead of caustic soda in the preparation of methane.

(ii) List two physical properties of methane.

(iii) A hydrocarbon with a vapour density of 29 contains 82.76% carbon and 17.24% hydrogen. Determine the: I. empirical formula; II. molecular formula of the hydrocarbon. [ H = 1.00 C = 12.00 ]

 

(b)(i) What is meant by the term isomerism?

(ii) Draw the structures of the two isomers of the compound with the molecular formula C\(_2\)H\(_6\)O.

(iii) Give the name of each of the isomers in (b)(ii).

(iv) State the major difference between the isomers.

 

(c) Give three deductions that could be made from the qualitative and quantitative analysis of a given organic compound.

(d) Give one chemical test to distinguish between propene and propane.

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