10.3. Air quality and climate
A subsection of Chemistry, 0620, through 10. Chemistry of the environment
Listing 10 of 389 questions
The diagram shows the composition of the planet Saturn. liquid hydrogen liquid helium atmosphere rocky core 75.0% hydrogen 24.9% helium 0.1% other gases Describe how Saturn’s atmosphere differs from the Earth’s atmosphere. Give three differences. Some properties of hydrogen and helium are given in the table. element density of the liquid in g / cm3 melting point in °C boiling point in °C hydrogen 0.07 –259 –253 helium 0.15 –272 –269 Use the information to suggest why the layer of liquid hydrogen in Saturn floats on top of the liquid helium. What is the physical state of hydrogen at –250 °C? Explain your answer. The atmosphere of Saturn contains small amounts of ammonia. Describe a test for ammonia. test result Ammonia is a covalent compound. Complete the diagram to show ● the arrangement of electrons in a molecule of ammonia, ● the symbols of the atoms present. Show outer electrons only. Saturn’s atmosphere also contains small amounts of ammonium hydrosulfide. Calculate the relative molecular mass of ammonium hydrosulfide, NH4SH. Use your Periodic Table to help you. relative molecular mass = Saturn’s atmosphere also contains small amounts of methane. Small amounts of methane are present in the Earth’s atmosphere. Methane is a greenhouse gas. Name another greenhouse gas present in the Earth’s atmosphere. Scientists are concerned about the increase in the amount of greenhouse gases in the Earth’s atmosphere. Explain why.
0620_w17_qp_32
THEORY
2017
Paper 3, Variant 2
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Oxides of nitrogen are pollutants in the air. One source of oxides of nitrogen in the air is from the manufacture of nitric acid. State one other source of oxides of nitrogen in the air. State one adverse effect of oxides of nitrogen on health. Oxides of nitrogen act as catalysts. What is meant by the term catalyst ? Oxides of nitrogen are formed during the manufacture of nitric acid. Which one of the pH values could be the pH of nitric acid? Draw a circle around the correct answer. pH 1 pH 7 pH 10 pH 14  Nitrogen is present in fertilisers. Why are fertilisers added to the soil where crops are grown? The table shows some observations about the reactivity of four metals with dilute hydrochloricacid. metal reaction with hydrochloric acid calcium a rapid stream of bubbles is seen lead no bubbles are seen manganese a slow stream of bubbles is seen tin a few bubbles slowly form Use the information in the table to put the four metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive  Calcium melts at 839 °C and boils at 1484 °C. What is the physical state of calcium at 1600 °C? 
0620_s19_qp_32
THEORY
2019
Paper 3, Variant 2
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This question is about compounds of nitrogen. Nitrogen reacts with lithium to form lithiumnitride, Li3N. Write the chemical equation for the reaction between lithium and nitrogen. Lithiumnitride is ionically bonded. Complete the diagram to show the electronic structure of the nitride ion. Show the charge on the nitride ion. N  Nitrogen reacts with fluorine to form nitrogen trifluoride, NF3. The chemical equation can be represented as shown. N≡N + 3 F–F 2 F–N–F F Some bond energies are shown in the table. bond bond energy in kJ / mol N≡N F–F N–F Calculate the energy change for the reaction between nitrogen and fluorine, using the following steps: ● energy taken in to break bonds  kJ ● energy released when bonds are formed  kJ ● energy change during the reaction.  kJ / mol  Use your answer to to deduce whether this reaction is endothermic or exothermic. Explain your answer. Complete the dot-and-cross diagram to show the electron arrangement in a molecule of NF3. Use dots for nitrogen electrons and crosses for fluorine electrons. Show outer electrons only. F F F N  Lithiumnitride melts at 813 °C. Nitrogentrifluoride melts at –206 °C. Explain in terms of attractive forces why lithiumnitride has a much higher melting point than nitrogentrifluoride. In your answer refer to the types of attractive forces between particles and their relative strengths. Ammoniumnitrate, NH4NO3, is a compound of nitrogen. Calculate the percentage by mass of nitrogen in ammoniumnitrate.  percentage by mass of nitrogen = State a use of ammoniumnitrate in agriculture. State the name of a compound that will displace ammonia from ammoniumnitrate. Ammonia is a base which forms a weakly alkaline solution when dissolved in water. Define the term base. Suggest the pH of aqueous ammonia. 
0620_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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Nitric acid is now made by the oxidation of ammonia. It used to be made from air and water. This process used very large amounts of electricity. Air was blown through an electric arc and heated to 3000 °C. N2+ O22NOequilibrium 1 nitric oxide The equilibrium mixture leaving the arc contained 5 % of nitric oxide. This mixture was cooled rapidly. At lower temperatures, nitric oxide will react with oxygen to form nitrogen dioxide. 2NO+ O22NO2 equilibrium 2 Nitrogen dioxide reacts with oxygen and water to form nitric acid. Suggest a reason why the yield of nitric oxide in equilibrium 1 increases with temperature. What effect, if any, would increasing the pressure have on the percentage of nitric oxide in equilibrium 1? Explain your answer. Deduce why equilibrium 2 is only carried out at lower temperatures. Complete the equation for the reaction between nitrogen dioxide, water and oxygen to form nitric acid. NO2 + O2 + → HNO3 Ammonia is more expensive than water and air. Suggest a reason why the ammonia-based process is preferred to the electric arc process. Nitric acid is used to make the fertiliser ammonium nitrate, NH4NO3. What advantage has this fertiliser over another common fertiliser, ammonium sulfate, (NH4)2SO4? Plants need nitrogen to make chlorophyll. Explain why chlorophyll is essential for plant growth.
0620_w13_qp_32
THEORY
2013
Paper 3, Variant 2
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Questions Discovered
389