A sample of orange juice is suspected to have been contaminated with a yellow dye. Which of the following methods can be used to detect the dye?

• A. Decantation
• B. Chromatography
• C. Distillation
• D. Filtration

Which of the following hydrocarbons is mainly used as fuel?

• A) Methylene
• B) Ethylene
• C) Methane
• D) Ethyne

(a) What is the change in oxidation state of chromium in the reaction represented by the following equation?

3SO\(_2\) + Cr\(_2\)O\(^2_{-7}\) + 2H\(^+\) -> 3SO\(_4^{2-}\) + 2Cr\(^{3+}\) + H\(_2\)O

(b) Use the half equations given below to deduce the equation for the reaction between iron(II) ions and heptaoxodichromate (VI) ions in acidic solution.

Fe\(^{2+}\) --> Fe\(^{3+}\) + e\(^-\)

Cr\(_2\)O\(^{2-}_7\) + 14H\(^+\) + 6e\(^-\) ----> 2Cr\(^{3+}\) + 7H\(_2\)O.

As the concentration of an electrolyte reduces, the conductivity

• A. reduces to zero
• B. decreases
• C. increase
• D. is unaffected

Which of the following statements about Group VII elements is correct?

• A. they are present in the same physical state
• B. they are strong reducing agents
• C. their reactivity decreases down the group
• D. they exist as monoatomic molecules

The products of the reaction between CH3CH 2COOH and CH3OH are H 2 O and

• A. CH3CH2COOCH3
• B. CH3CH2COOCH2CH 3
• C. CH3CH2CH2COOH
• D. CH3CH2CH2OH

The nucleus of an atom consists of?

• A. Electrons and neutrons
• B. Electrons and protons
• C. Protons and neutrons
• D. None of the above

Polyatomicity is illustrated by molecules of

• A. sulphur
• B. carbon (IV) oxide
• C. noble gases
• D. liquefied oxygen

When iron rusts, it undergoes

• A. deliquescence
• B. chemical decomposition
• C. hydrolysis
• D. redox reaction

(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.