(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.
(a) Equations
- (i) Beta decay of sodium-24: \[^{24}_{11}Na \rightarrow\ ^{24}_{12}Mg +\ ^{0}_{-1}e\]
- (ii) Sodium with cold water: \[2Na + 2H_2O \rightarrow 2NaOH + H_2\]
(b)(i) Two differences between reaction (a)(i) and (a)(ii)
- (a)(i) is a nuclear reaction taking place in the nucleus; (a)(ii) is a chemical reaction involving only the valence electrons.
- In (a)(i) a new element (Mg) is formed and an enormous amount of energy is released; in (a)(ii) no new element is formed and comparatively little energy is released, and its rate is affected by temperature/catalyst while (a)(i) is not.
(b)(ii) Two applications of radioactive decay: use of radioisotopes in medicine (radiotherapy for cancer, diagnostic tracers); and carbon-14 dating to estimate the age of fossils and rocks (also generation of electricity in nuclear reactors).
(c) Mg + 2HCl → MgCl2 + H2
- (i) Type of reaction: displacement (redox) reaction.
- (ii) Made faster by: warming (raising the temperature); using a more concentrated acid; or using powdered magnesium to increase surface area.
- (iii) Moles of Mg \(= \frac{6.0}{24} = 0.25\text{ mol}\); 1 mol Mg gives 1 mol H2, so \[V = 0.25 \times 22.4 = 5.6\text{ dm}^3\]
(d) (i) An electrolyte is a substance which, when molten or in aqueous solution, conducts electricity and is decomposed by it. (ii) Electrolysis is the decomposition of an electrolyte by the passage of an electric current through it in the molten or aqueous state.
(e)
- (i) Metal extracted by electrolysis: aluminium (or sodium).
- (ii) Its ore: bauxite.
- (iii) Electrolysis of dilute NaCl with graphite electrodes: hydrogen is discharged at the cathode and oxygen at the anode.
- (iv) Aqueous NaCl conducts because its ions are free to move and carry charge, whereas in solid NaCl the ions are held rigidly in the lattice and cannot move.
- (v) Industrial use of NaCl: raw material for the manufacture of chlorine, sodium hydroxide and sodium trioxocarbonate(IV) (also food preservation).
(a) Equations
- (i) Beta decay of sodium-24: \[^{24}_{11}Na \rightarrow\ ^{24}_{12}Mg +\ ^{0}_{-1}e\]
- (ii) Sodium with cold water: \[2Na + 2H_2O \rightarrow 2NaOH + H_2\]
(b)(i) Two differences between reaction (a)(i) and (a)(ii)
- (a)(i) is a nuclear reaction taking place in the nucleus; (a)(ii) is a chemical reaction involving only the valence electrons.
- In (a)(i) a new element (Mg) is formed and an enormous amount of energy is released; in (a)(ii) no new element is formed and comparatively little energy is released, and its rate is affected by temperature/catalyst while (a)(i) is not.
(b)(ii) Two applications of radioactive decay: use of radioisotopes in medicine (radiotherapy for cancer, diagnostic tracers); and carbon-14 dating to estimate the age of fossils and rocks (also generation of electricity in nuclear reactors).
(c) Mg + 2HCl → MgCl2 + H2
- (i) Type of reaction: displacement (redox) reaction.
- (ii) Made faster by: warming (raising the temperature); using a more concentrated acid; or using powdered magnesium to increase surface area.
- (iii) Moles of Mg \(= \frac{6.0}{24} = 0.25\text{ mol}\); 1 mol Mg gives 1 mol H2, so \[V = 0.25 \times 22.4 = 5.6\text{ dm}^3\]
(d) (i) An electrolyte is a substance which, when molten or in aqueous solution, conducts electricity and is decomposed by it. (ii) Electrolysis is the decomposition of an electrolyte by the passage of an electric current through it in the molten or aqueous state.
(e)
- (i) Metal extracted by electrolysis: aluminium (or sodium).
- (ii) Its ore: bauxite.
- (iii) Electrolysis of dilute NaCl with graphite electrodes: hydrogen is discharged at the cathode and oxygen at the anode.
- (iv) Aqueous NaCl conducts because its ions are free to move and carry charge, whereas in solid NaCl the ions are held rigidly in the lattice and cannot move.
- (v) Industrial use of NaCl: raw material for the manufacture of chlorine, sodium hydroxide and sodium trioxocarbonate(IV) (also food preservation).
