Practice Paper 2 (DP IB Chemistry: SL)

Ammonia gas can be synthesized by the direct combination of nitrogen gas and hydrogen gas. When the two gases are reacted together in a sealed container the following equilibrium reaction takes place:

N₂ (g)  + 3H₂ (g) ⇌ 2NH₃ (g)            ∆H = -92.6 kJ

Describe two characteristics of a reaction in a state of dynamic equilibrium.

Write the equilibrium constant expression, K_c, for the reaction in part (a).

Explain, with a reason, how each of the following changes can affect the position of equilibrium in part (a).

Ammonia is manufactured industrially by the Haber process in which iron is used as a catalyst. Explain the effect of a catalyst on the position of equilibrium and the value of K_c.

Molten potassium bromide can be electrolysed using graphite electrodes.

State the half equations for the oxidation and reduction processes and deduce the overall cell reaction, including state symbols. 

Explain why solid potassium bromide does not conduct electricity. 

A voltaic cell is made from a half-cell containing a magnesium electrode in a solution of magnesium nitrate and a half-cell containing a silver electrode in a solution of silver(I) nitrate.

Organic compounds are classified into families called a homologous series.

State three features of members belonging to the same homologous series.

Table 1 shows the boiling points of the first five members of the alkane family.

 Table 1

On the axes below in Figure 1, draw a graph of boiling point against the number of carbon atoms in the alkanes. Estimate the boiling point of the next member of the homologous series, hexane, C₆H₁₄, and show on your graph how you arrived at your estimated boiling point. 

Figure 1

Estimated boiling point of hexane : ________ ^oC

State the general formula for an alkyne and give the molecular formula and name of the fifth member of the alkyne family.

Outline the difference between quantitative and qualitative data.

A student uses a thermometer to measure the temperature of a beaker of water, before and after heating. The smallest thermometer division is 1.0 ^oC. The initial temperature of the water is 23.0 ^oC.

How should the temperature change be recorded?

This question is about precision....

How should the volume delivered be recorded?

 [1]

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

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.

Silicon dioxide has a similar name to carbon dioxide, but its boiling point is 2230 ℃.

Briefly outline the reason for this difference.