2011年11月IB化学SL真题下载-Paper2
1. Airbags are an important safety feature in vehicles. Sodium azide, potassium nitrate and silicon dioxide have been used in one design of airbag.
Sodium azide, a toxic compound, undergoes the following decomposition reaction under certain conditions.
2NaN3 (s)→2Na (s) + 3N2 (g)
Two students looked at data in a simulated computer-based experiment to determine the volume of nitrogen generated in an airbag.
(a) Sodium azide involves ionic bonding, and metallic bonding is present in sodium.Describe ionic and metallic bonding.
(b) Using the simulation programme, the students entered the following data into the computer.
(i) State the number of significant figures for the temperature, mass and pressure data.
T:
m:
p:
(ii) Calculate the amount, in mol, of sodium azide present.
(iii) Determine the volume of nitrogen gas, in dm3, produced under these conditions based on this reaction.
(c) The chemistry of the airbag was found to involve three reactions. The first reaction involves the decomposition of sodium azide to form sodium and nitrogen. In the second reaction, potassium nitrate reacts with sodium.
2KNO3(s) + 10Na(s)→ K2O(s) + 5Na2O(s) + N2(g)
(i) Suggest why it is necessary for sodium to be removed by this reaction.
(ii) The metal oxides from the second reaction then react with silicon dioxide to form a silicate in the third reaction.
K2O(s) + Na2O(s) + SiO2(s)→ Na2K2SiO4(s)
Draw the structure of silicon dioxide and state the type of bonding present.
Structure:
Bonding:
(d) An airbag inflates very quickly.
(i) It takes just 0.0400 seconds to produce nitrogen gas in the simulation. Calculate the average rate of formation of nitrogen in (b) (iii) and state its units.
(ii) The students also discovered that a small increase in temperature (e.g. 10 °C) causes a large increase (e.g. doubling) in the rate of this reaction. State one reason for this.
2. Isotopes are atoms of the same element with different mass numbers. Two isotopes of cobalt are Co-59 and Co-60.
(a) Deduce the missing information and complete the following table.
(b) State why the Co-60 radioisotope is used in radiotherapy.
3. (a) Molten sodium chloride can be electrolysed using graphite electrodes.
(i) Draw the essential components of this electrolytic cell and identify the products that form at each electrode.
Product formed at positive electrode (anode):
Product formed at negative electrode (cathode):
(ii) State the half-equations for the oxidation and reduction processes and deduce the overall cell reaction, including state symbols.
Oxidation half-equation:
Reduction half-equation:
Overall cell reaction:
(b) Explain why solid sodium chloride does not conduct electricity.
(c) Using another electrolysis reaction, aluminium can be extracted from its ore, bauxite,which contains Al2O3. State one reason why aluminium is often used instead of iron in many engineering applications.
2011年11月IB化学SL真题余下省略！
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