Mock Exam Set 1 - Paper 2

[Maximum mark: 15]

A solution of calcium chlorate $\ce{Ca(ClO3)2 }$ is made by dissolving 4.164 $g$ in 150.0 $cm^3$ of water.
The resulting solution of calcium chlorate has a concentration of 0.1142 $mol\ dm^{-3}$.

1. Determine the number of moles and the mass of calcium chlorate present in the solution. [2]
   

2. The calcium chlorate solution made above is then mixed with 200.0 $cm^3$ of 0.07500 $mol \ dm^{-3}$ sodium phosphate $\ce{(Na3PO4 )}$, producing a precipitate of calcium phosphate, $\ce{Ca3(PO4)2}$.

   1. Write the net ionic equation for this reaction, including state symbols. [1]
      
   2. Determine the limiting reactant in this reaction, showing your work. [2]
      
   3. If 1.535 $g$ of calcium phosphate is recovered, determine the percentage yield in this reaction. [2]
      

3. Like calcium, magnesium is an element in group 2 of the periodic table.

   1. State the full electron configuration for magnesium and the block it can be found in the periodic table. [2]
      
   2. Explain how successive ionization energies can prove that magnesium is in group 2 and period 3 of the periodic table. [2]
      
   3. State an equation for the reaction between magnesium oxide and water, and comment on the pH of the resultant solution. [2]
      
   4. By referring to their relative ionization energies’ trend, compare and explain the metallic behavior of magnesium to calcium and beryllium (values from the data booklet are not required). [2]
      

[Maximum mark: 11]

Ethanoic acid has a boiling point of 118°C and is soluble in water. The structural formula of ethanoic acid is shown.

1. State the strongest type of intermolecular interaction formed by ethanoic acid. [1]
   

2. When ethanoic acid dissolves in water, it reacts to form an ethanoate ion $\ce{CH3COO^-}$.

   1. Write an equation showing the resonance in the ethanoate ion. Include in it, the structural formulas for the two resonance structures, showing all charges and non-bonding electron pairs. [2]
      
   2. Explain how the dissolution of ethanoic acid in water affects the electrical conductivity of the liquid. [1]
      

3. Esterification is a reversible process that occurs between alcohols and carboxylic acids. One example of esterification is the reaction between ethanol and ethanoic acid to produce ethyl ethanoate and water.

   $\ce{CH3COOH (l) + CH3CH2OH (l) ⇋ CH3COOCH2CH3 (l) + H2O (l)}$

   1. Ethanol and ethanoic acid were added to the reaction vessel, and $Q$ was calculated before equilibrium was reached. State the relationship between the values of $Q$ and $K_c$. [1]
      
   2. Use section 13 of the data booklet to calculate the enthalpy change for the forward reaction (${\Delta{H_c} \ce{(H2O)}}$ = 0 $kJ\ mol^{-1}$). [1]
      
   3. Use your answer to (ii) to predict and explain how the value of $K_c$ and the equilibrium yield of the ester will change with increasing temperature. [3]
      

4. The condensed structural formulas of two other organic compounds, A and B, are shown.

   

   1. Suggest why the boiling points of A and B are different. [1]
      
   2. Explain why A and B are not soluble in water. [1]
      

[Maximum mark: 9]

Compound Z is a colourless liquid with an unpleasant smell. It is found naturally in some plants, such as vanilla.
The full structural formula of compound Z is shown.

1. State the IUPAC name of compound Z. [1]
   

2. The pH of an aqueous solution of compound Z differs from that of pure water. Explain this observation. [2]
   

3. Compound Z is produced by reacting compound X with potassium dichromate(VI), as shown. Compound Y is an intermediate of the reaction.

   

   1. Draw the full structural formula of compound Y. [2]
      

   2. The infrared spectrum of one compound in the reaction mixture is shown.

      

      Using section 26 of the data booklet, state the compound that produced this spectrum and give two reasons for your answer. [2]
      

   3. Compound Y can be separated from compounds X and Z by fractional distillation of the reaction mixture.
      Explain how differences in the intermolecular bonding of compounds X, Y and Z allow compound Y to be removed by fractional distillation. [2]
      

[Maximum mark: 6]

A student adds excess zinc pellets to 100.0 $cm^3$ of 0.100 $mol\ dm^{-3}\ \ce{HNO3}$ in a beaker. The student tracks the reaction's progress by monitoring the mixture's pH in the beaker over time. The data is collected and graphed. The results are shown below:

1. Draw a line on the graph showing how the pH would change if a solid strip of zinc with equal mass was added to the nitric acid rather than zinc pellets. [1]
   

2. 1. On the energy profile diagram below, label lines A and B. Then, state if the reaction is endothermic or exothermic and justify your response. [4]
      

   

   2. If the energy profile diagram above represents the reaction with a catalyst, sketch how the curve would change if the reaction proceeded without a catalyst. [1]
      

[Maximum mark: 9]

One of the main components of the aluminium ore bauxite is aluminium oxide, $\ce{Al2O3}$.
The ore may be converted to useful materials using both chemical and electrochemical processes.

1. Aluminium oxide reacts with hot concentrated sodium hydroxide to form sodium tetrahydroxoaluminate, $\ce{NaAl(OH)4}$. The equation for this reaction is shown.

   $\ce{Al2O3 (s) + a NaOH (aq) + b H2O (l) → c NaAl(OH)4 (aq)}$

   1. State the coefficients a, b and c in this equation. [2]
      
   2. Draw the Lewis structure of the $\ce{Al(OH)4^-}$ ion. [1]
      
   3. State the O-Al-O bond angle in the $\ce{Al(OH)4^-}$ ion. [1]
      
   4. State why aluminium oxide does not act as a Brønsted-Lowry acid in this reaction. [1]
      

2. The apparatus used to convert aluminium oxide to pure aluminium metal is shown.

   

   The equation for the overall reaction is shown.

   $\ce{2Al2O3 (cryolite) + 3C (s) → 4Al (l) + 3CO2 (g)}$

   1. Write a half-equation for the reduction of the dissolved aluminium ions. [1]
      
   2. Explain, using section 25 of the data booklet, why the production of aluminium is an example of electrolysis. [1]
      
   3. The standard enthalpies of formation for selected reactants and products are given in the table.

   Material	Standard enthalpy of formation / $kJ mol^{-1}$
   $\ce{Al2O3}$ (cryolite)	-1456
   Al (l)	+10

   Calculate the enthalpy change of the reaction, $\Delta{H_r}$, in $kJ mol^{-1}$, using section 12 of the data booklet.
   You may assume that the enthalpies of formation for reactants and products not listed in the table are equal to their values under SATP conditions. [2]