Practice Paper 2 (DP IB Chemistry: HL)

The successive ionisation energies of vanadium are shown.

State the sub-levels from which each of the first four electrons are lost

Outline why there is an increase in ionisation energy from electron 3 to electron 5.

Explain why there is a large increase in the ionisation energy between electrons 5 and 6.

The first six ionisation energies, in kJ mol^-1, of an element are shown below 

Explain the large increase in ionisation energy from IE₃ to IE₄

The hydrogen halides do not show perfect periodicity. A bar chart of boiling points, as seen in Figure 1, shows that the boiling point of hydrogen fluoride, HF, is much higher than periodic trends would indicate.

Figure 1

Explain why the boiling point of HF is much higher than the boiling point of the other hydrogen halides.

There is an increase in boiling point moving from HCl to HI.

Explain this trend in boiling points of the hydrogen halides.

A student adds a solution containing silver ions to two test tubes containing chloride   and bromide ions. The student observes that both solutions turn cloudy.

Explain the observation the student made upon carrying out the experiment.

When chromium(III) sulfate dissolves in water, a green solution containing the [Cr(H₂O)₆]³⁺ ion forms.

Vanadium(V) oxide is the catalyst used in the Contact process as shown by the reactions:

i)     Explain, using the equations, why V₂O₅ is a catalyst.

ii)     Explain why V₂O₅ can act as a catalyst in this reaction.

Excess ammonia is added to a solution of Cu²⁺ ions resulting in the substitution of 4 ligands.

Using section 15 of the data booklet, explain why this reaction results in a shift in the wavelength of light absorbed by the Cu²⁺ complex.

Draw the structure of silicon dioxide and state the type of bonding present.

Describe the similarities and differences you would expect in the properties of silicon and diamond.

The boiling point of diamond is 3550 ℃, but for carbon dioxide it is -78.5 ℃. Both are covalent substances. 

Explain this difference with reference to structure and bonding.

Ibuprofen is a common non-steroidal anti-inflammatory drug (NSAID). It contains a benzene ring and a carboxylic acid at the end of one of the branches.

Deduce the number of resonance structures possible in the deprotonated form of ibuprofen.

Deduce the number of:

[1]

[1]

The ibuprofen molecule contains both sp³ and sp² hybridised orbitals.

[1]

[1]

Explain why the benzene ring is a regular, planar hexagon.

State the formula for calculating the standard enthalpy change of reaction, ΔH_r, using bond energies.

Use section 11 of the data booklet to calculate the enthalpy change, in kJ mol^-1, for the following reaction.    

Cl₂ + H₂ → 2HCl 

State whether the energy change for the reaction in part (b) is endothermic or exothermic.

Using section 11 of the data booklet, calculate the enthalpy change of reaction, ΔH_r, in kJ mol^-1 for the following reaction.

CH₄ + Cl₂ → CH₃Cl + HCl 

A student measured the energy change when 1.35 g of zinc was added to 50 cm³ of 0.5 mol dm^-3 copper sulfate, CuSO₄ (aq), solution. The initial temperature of 21 ^oC was recorded before the addition of the zinc and a temperature reading was taken every 30 seconds.

Use the graph to determine the overall temperature change for the reaction

Calculate the enthalpy change for the reaction in kJ mol^-1.

Calculate the percentage error between your value for the enthalpy change of reaction and the literature value of -217 kJ mol^-1. Give your answer to two significant figures. 

Explain why your calculated value for the enthalpy change of reaction is different from the literature value of -271 kJ mol^-1. 

Define the term nucleophile. 

Explain why the hydroxide ion, OH^- , is a stronger nucleophile than water. 

State the two ways a nucleophilic substitution reaction can occur. 

State the the name of the mechanism occurring in the image below which will form ethanol in one step. 

Ethane-1,2-diol, C₂H₆O₂, can be distinguished from ethanedioic acid,C₂H₂O₄, by a number of analytic techniques including MS, IR and NMR 

The MS of these molecules is shown below. 

Which spectrum belongs to each molecule? Justify your answer.

 

Spectrum A

Spectrum B

The IR spectra of ethane-1,2-diol, C₂H₆O₂, and ethanedioic acid dihydrate,C₂H₂O₄.2H₂O, are shown in spectrum C and D. Use Section 26 of the Data Booklet to answer this question.

Spectrum CSpectrum D

Which spectrum belongs to each molecule? Justify your answer.

The ¹H NMR spectrum of ethane-1,2-diol is shown in spectrum E. Explain the significance of the spectrum.

The Winkler method is a chemical technique used to measure the concentration of dissolved oxygen in water samples. The method involves treating the samples to convert the dissolved oxygen into iodine which is then titrated against standard sodium thiosulfate solution as shown below:

Step 1:             2Mn²⁺ (aq) + O₂ (aq) + 4OH⁻ (aq) → 2MnO₂ (s) + 2H₂O (l)

Step 2:             MnO₂ (s) + 2I⁻ (aq) + 4H⁺ (aq) → Mn²⁺ (aq) + I₂ (aq) + 2H₂O (l)

Step 3:             2S₂O₃²⁻ (aq) + I₂ (aq) → 2I⁻ (aq) + S₄O₆²⁻ (aq)

A student wanted to check if the water in a fish tank was sufficiently oxygenated and analysed two 500 cm³ samples, five days apart.

The following results in Table 1 were obtained when the resulting iodine was titrated against 0.0120 moldm^-3 Na₂S₂O₃ (aq).

Table 1

Oxygen analysis in fish tank water on day 0

Determine the number of moles of oxygen in the 500 cm³ sample and hence the concentration in ppm.

It is generally considered that dissolved oxygen levels of at least 4-5 ppm are sufficient for most aquatic life. The day 5 sample contained 5.03 × 10⁻⁵ moles of oxygen.

Discuss whether the student should be concerned about the oxygen levels in the fish tank over the 5-day period.

Suggest two modifications to the procedure which would make the result more reliable.