(a) Write the molecular formula of X.
(i) What type of reaction is represented by the equation?
(ii) Consider the following reaction equation: \( \mathrm{C_{12}H_2 \to X + C_8H_{18}} \)
(iii) Draw the structure of two isomers of X.
(iv) Name the isomers drawn in (a)(iii).
(v) Write a balanced equation for the reaction between X and hydrogen.
(b) Describe one test for fats.
(c) Sulphur (IV) oxide is converted to tetraoxosulphate (VI) acid according to the following equation: \( \mathrm{2SO_{2(g)} + O_{2(g)} + 2H_2O_{(l)} \to 2H_2OSO_{4(aq)}} \). If 1.5 moles of oxgen reacts with sulphur (IV) oxide, calculate the mass of tetraoxosulphate (VI) acid produced. [H = 1.0; O = 16.0; S = 32.0].
(d) Consider the following neutralization reaction:
\( \mathrm{CH_3COOH + NaOH \to CH_3COONa + H_2O;} \ \bigtriangleup H_1 \)
\( \mathrm{CH_3COOH + NH_4OH \to CH_3COONH_4 + H_2O;} \ \bigtriangleup H_2 \)
\( \mathrm{NaOH + HCl \to NaCl + H_2O} \ \bigtriangleup H_3 \)
(i) Arrange the enthalphy changes for the reactions in order of increasing magnitude.
(ii) Explain briefly your order in (d)(i).
(e) Consider the following substances. \( \mathrm{Cu_{(s)}} \), \( \mathrm{BeCl_2} \), \( \mathrm{NaH_{(s)}} \), \( \mathrm{HF_{(s)}} \)and \( \mathrm{CCl_{4(l)}} \). State the substance(s) which;
(i) can conduct electricity;
(ii) is/are soluble in water.
From \(C_{12}H_{26} \rightarrow X + C_8H_{18}\), balancing gives X = C4H8 (an alkene, butene).
(a) Molecular formula of X: C4H8.
(i) The reaction is cracking (thermal/catalytic decomposition of a large alkane into a smaller alkane and an alkene).
(iii) Two isomers of C4H8
But-1-ene: CH2=CH-CH2-CH3
But-2-ene: CH3-CH=CH-CH3
(iv) The isomers are but-1-ene and but-2-ene.
(v) Reaction of X with hydrogen (nickel catalyst):
\[C_4H_8 + H_2 \rightarrow C_4H_{10}\]
(b) Test for fats: rub the substance on a piece of paper; a fat leaves a translucent (greasy) spot that does not disappear on gentle warming.
(c) \(2SO_2 + O_2 + 2H_2O \rightarrow 2H_2SO_4\). Molar mass of H2SO4 = \(2 + 32 + 64 = 98\).
1 mol O2 gives 2 mol H2SO4, so 1.5 mol O2 gives \(1.5 \times 2 = 3\ \text{mol}\) H2SO4.
Mass \(= 3 \times 98 = 294\ \text{g}\).
(d)(i) Increasing magnitude: \(\Delta H_2 < \Delta H_1 < \Delta H_3\).
(ii) \(\Delta H_3\) (strong acid + strong base) is the most exothermic because both are fully ionized, so the full heat of neutralization is released. \(\Delta H_1\) (weak acid + strong base) is smaller because some energy is used to complete the ionization of the weak acid. \(\Delta H_2\) (weak acid + weak base) is the smallest because energy is absorbed to ionize both the weak acid and the weak base.
(e)(i) Can conduct electricity: Cu(s) (a metal with mobile electrons).
(ii) Soluble in water: BeCl2 and HF.
From \(C_{12}H_{26} \rightarrow X + C_8H_{18}\), balancing gives X = C4H8 (an alkene, butene).
(a) Molecular formula of X: C4H8.
(i) The reaction is cracking (thermal/catalytic decomposition of a large alkane into a smaller alkane and an alkene).
(iii) Two isomers of C4H8
But-1-ene: CH2=CH-CH2-CH3
But-2-ene: CH3-CH=CH-CH3
(iv) The isomers are but-1-ene and but-2-ene.
(v) Reaction of X with hydrogen (nickel catalyst):
\[C_4H_8 + H_2 \rightarrow C_4H_{10}\]
(b) Test for fats: rub the substance on a piece of paper; a fat leaves a translucent (greasy) spot that does not disappear on gentle warming.
(c) \(2SO_2 + O_2 + 2H_2O \rightarrow 2H_2SO_4\). Molar mass of H2SO4 = \(2 + 32 + 64 = 98\).
1 mol O2 gives 2 mol H2SO4, so 1.5 mol O2 gives \(1.5 \times 2 = 3\ \text{mol}\) H2SO4.
Mass \(= 3 \times 98 = 294\ \text{g}\).
(d)(i) Increasing magnitude: \(\Delta H_2 < \Delta H_1 < \Delta H_3\).
(ii) \(\Delta H_3\) (strong acid + strong base) is the most exothermic because both are fully ionized, so the full heat of neutralization is released. \(\Delta H_1\) (weak acid + strong base) is smaller because some energy is used to complete the ionization of the weak acid. \(\Delta H_2\) (weak acid + weak base) is the smallest because energy is absorbed to ionize both the weak acid and the weak base.
(e)(i) Can conduct electricity: Cu(s) (a metal with mobile electrons).
(ii) Soluble in water: BeCl2 and HF.
