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2007 WAEC Chemistry Theory (a) Write an equation in each case to represent the (i) \(\beta\)-decay of \(^{24}_{11}Na\) to...

Chemistry
WAEC 2007

(a) Write an equation in each case to represent the (i) \(\beta\)-decay of \(^{24}_{11}Na\) to give Mg.

ii) reaction of sodium with cold water.

 

b)(i) State two differences between reaction (a)(i) and (ii)

ii) State two applications of the type of reaction represented in(a)(i)

 

(c) Consider the reaction represented by the equation:

Mg\(_{(s)}\) + 2HCI\(_{(aq)}\) \(\to\) MgCl\(_{(aq)}\) + H\(_{(q)}\)

(i) Name the type of reaction involved

(ii) Give two ways by which the reaction could be made faster.

(iii) What volume of hydrogen gas would be produced from 6.0 g of the magnesium? [ H = 1; 1 mole of gas occupy 22.4 dm\(^3\) at s.t.p. ]

 

(d) What is (i) an electrolyte?; (ii) electrolysis?

 

(e)(i) Give one metal that is extracted using electrolytic process.

(ii) Name the ore of the metal.

(iii) What is the substance discharged at each electrode when dilute NaCI is electrolysed using graphite electrodes?

(iv) Why would aqueous NaCI conduct electricity but solid NaCI would not?

(v) Give one industrial use of NaCI.

 

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Explanation

(a) (i)

\(^{24}_{11}Na\) \(\to\) \(^{24}_{12}Mg\) + \(_1\beta\)

(ii) 2Na\(_{(s)}\) + 2H\(_2\)O\(_{(l)}\) \(\to\) 2NaOH\(_{(aq)}\) + H\(_{2(g)}\)

 

(b)

Reaction (i)

Reaction(i)

Takes place in the nucleus or nucleus reaction

Takes place in the valence shell or chemical reaction

Large amount of heat is released

Small amount of heat is released

Involves proton, neutrons and electrons.

Involves valence electrons

New nuclides are formed

Newxompounds are formed

Not affected by external factors e.g temperature, pressure, catalyst.

Usually affected by external factors.

 

(ii) Sterilizing instruments

-- treatment of cancer

- carbon dating

- pest control, etc.

 

(c)(i) Displacement reaction.

(ii) using Mg powder i.e increasing the surface area of Mg.

- using higher concentration of HCI

- increase temperature of the reaction mixture.

 

(iii) 24g Mg =  22.4 dm\(^3\) of H\(_2\) gas

6g Mg = \(\frac{6g \times 22.4 dm^3}{24g}\)

  = 5.6 dm\(^3\).

 

(d)(i) An electrolyte is a compound which when molten or in aqueous solution will conduct electricity.

(ii) Electrolysis is the decomposition of an electrolyte by the passage of an electric current.

 

(e)(i) Aluminium

(ii) Bauxite

(iii) Cathode

- Hydrogen Anoda

- Oxygen

(iv) In the liquid state the Na+ and CI\(^-\) ions are mobile while in the solid state the ions ere in fixed position and cannot conduct electricity.

(v) Industrial uses of NaCI In the manufacture of CI\(_{2(g)}\)

— Salting out in soap manufacture

— Production of NaOH

— Solvay process

 

 

 

 


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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995