Practice Paper 2 (HL IB Chemistry)

Carvone is an organic compound containing carbon hydrogen and oxygen.

Complete combustion of 0.1526 g carvone produces 0.4470 g of carbon dioxide and 0.1281 g of water. Determine the empirical formula of carvone, showing your working.

0.146 g sample of carvone, when vaporised, had a volume of 0.0341 dm³ at 150 ^oC and 100.2 kPa. Calculate its molar mass showing your working.

Using your answer to part b), determine the number of molecules of carvone in 0.146 g.

For each of the molecules below, draw the Lewis (electron dot) structure and use the valence shell electron pair repulsion theory (VSEPR) to predict the shape of each molecule.

Oxygen difluoride (OF₂), phosphorus trifluoride, (PF₃) and boron trichloride, (BCl₃).

Crystalline ionic compounds do not conduct electricity. 

State and explain in which states ionic compounds conduct electricity.

The melting point of sodium chloride, NaCl, is 801° C. 

Explain, with reference to structure and bonding, why sodium chloride melts at such a high temperature.

We can use electronegativity values to deduce whether a compound is likely to be ionic or covalent.

Use Section 9 of the Data Booklet to state and explain whether each of the following compounds are ionic or covalent:

   ICl

   SrCl₂

   RbI

   HI

Phosphine, PH₃, is a gas formed by heating phosphorous acid, H₃PO₃, in the absence of air, as shown in the equation below.

4H₃PO₃ (s) → PH₃ (g) + 3H₃PO₄ (s)

3.45 × 10⁻² mol of H₃PO₃ is completely decomposed by this reaction.

State the expected molecular shape and expected bond angle in PH₃ (g).

Calculate the volume of phosphine gas formed, in cm³, at 100 kPa pressure and 210 °C.

1.85 g of white phosphorus was used to make phosphine according to the equation.

P₄ (s) + 3OH⁻ (aq) + 3H₂O (l) → PH₃ (g) + 3H₂PO₂⁻ (aq)

This phosphorus was reacted with 75.00 cm³ of 4.50 mol dm^-3 sodium hydroxide solution. Deduce, showing your working, which was the limiting reagent. 

Using section 2 of the Data booklet determine the volume of phosphine, measured in cm³ at standard temperature and pressure, that was produced. Give your answer to 3 significant figures. 

This question looks at how the entropy change of water varies with temperature.

Standard entropies can be used to calculate the entropy change of a reaction, ΔS.
For example, for the formation of nitrogen monoxide from nitrogen and oxygen. 

NO (g) + O₃ (g) → NO₂ (g) + O₂ (g)

Use the data given to calculate the entropy change of the reaction between nitric oxide and ozone at 298K.

The contact process is a method used industrially to form sulfur trioxide, by reacting sulfur dioxide and oxygen together over a vanadium(V) oxide catalyst.

The equation for this reaction is shown below:

2SO₂ (g) + O₂ (g) ⇌ 2SO₃ (g)

The value for the free energy change is an indication whether the forward or backwardreaction is favoured.

The curve that we would expect to see for the reaction between sulfur dioxide and oxygen is shown below.

 Explain why the curve for this reaction is shifted to the right hand side.

In any chemical reaction, the particles will all be moving around in different directions, at different speeds, with different amounts of energy.

A Maxwell-Boltzmann distribution is a graph which shows the distribution of energy amongst particles within a chemical reaction. 

Figure 1 below shows the Maxwell-Boltzmann distribution in a sample of a gas at a fixed temperature, T₁. 

Figure 1

State why a Maxwell-Boltzmann distribution curve always starts at the origin and what the area under the curve represents.

Chemical reactions take place at different speeds. For a chemical reaction to take place, particles must collide with each other in the correct orientation and with sufficient energy. 

Give one reason why a reaction may be slow at room temperature.

Urea can be made by the direct combination of ammonia and carbon dioxide gases.

2NH₃ (g) + CO₂ (g)  CO(NH₂)₂ (g) + H₂O (g) 

Write the equilibrium constant expression, K_c.

ΔH < 0 for the forward reaction.

Predict the effect on the equilibrium constant, K_c, when the temperature is increased.

Predict what will happen to the equilibrium position if there is a decrease in pressure.

The K_c value for the reaction is determined to be 2 x 10^-9 mol dm^-3 at 298 K.

Determine the magnitude of K_c if the reaction is reversed.

Salicylic acid has the structure shown below in Figure 1.                             

Figure 1

Draw the structure of the conjugate base of salicylic acid, showing all the atoms and all the bonds.

Predict what would be seen if a small amount of copper (II) oxide was added to an aqueous solution of salicylic acid, HOC₆H₄COOH, and warmed.

Write a balanced equation for the reaction.

Suggest, with a reason, whether salicylic acid is likely to be soluble in water.

Determine the relative molecular mass, M_r, of salicylic acid using Table 6 from the Data book.

A student sets up a titration to determine the amount of iron(II) sulfate in an iron tablet. They titrate the iron(II) sulfate solution with potassium manganate(VII) solution.

The iron(II) sulfate solution is acidified before titration to stop the manganate ion forming unwanted manganese dioxide. 

Explain the effect that not acidifying the iron(II) sulfate would have on the final calculation of the estimated mass of iron.

The student dissolved the iron tablet in excess sulfuric acid and made the solution up to 250 cm³ in a volumetric flask. 25.0 cm³ of this solution was titrated with 0.0100 mol dm^-3 potassium manganate(VII) solution. The average titre was found to be 26.65 cm³ of potassium manganate(VII) solution. 

A reaction scheme for propene is shown below.

State the condensed structural formula of propene.

State the IUPAC names for compounds A, B and C shown in the reaction scheme in part (a)

Propene will also react to form an alcohol. State the reagents and conditions required for the formation of an alcohol from propene.