9. The Periodic Table: chemical periodicity
A section of Chemistry, 9701
Listing 10 of 288 questions
Use This question is about the properties and reactions of the oxides of some elements in their +4 oxidation state. Chlorine dioxide, Cl O2, is an important industrial chemical, used to bleach wood pulp for making paper, and to kill bacteria in water supplies. However, it is unstable and decomposes into its elements as follows. 2Cl O2Cl 2+ 2O2The chlorine atom is in the middle of the Cl O2 molecule. Using the chlorine-oxygen bond energy as 278 kJ mol–1, and other values from the Data Booklet, calculate DH for the above reaction. DH = kJ mol–1 Assuming the Cl -O bonds in chlorine dioxide are double bonds, predict the shape of the Cl O2 molecule. Explain your answer. Cl O2 can be made in the laboratory by reacting KCl O3 with concentrated H2SO4. Other products are K2SO4, KCl O4 and H2O. Construct a balanced equation for this reaction. You may find the use of oxidation numbers helpful. Sulphur dioxide is an atmospheric pollutant. State two sources of atmospheric SO2 that arise from human activity. Explain why SO2 is a pollutant, and state an environmental consequence of this pollution. Examiner’s Use All the oxides of the elements in Group IV in their +4 oxidation state are high melting point solids except CO2. Explain this observation by describing the bonding in CO2, SiO2 and SnO2. State the difference in the thermal stabilities of SnO2 and PbO2. Illustrate your answer with an equation. CO2 dissolves in water to form a weakly acidic solution containing the hydrogencarbonate ion. Write an equation for the reaction of CO2 with water, and write an expression for the equilibrium constant, Kc. Explain the role of the hydrogencarbonate ion in controlling the pH of blood, illustrating your answer with relevant equations.
9701_s08_qp_4
THEORY
2008
Paper 4, Variant 0
View
This question refers to the elements shown in the portion of the Periodic Table given below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr From this table, identify in each case one element that has the property described. Give the symbol of the element in each case. The element that has a molecule which contains exactly eight atoms. The element that forms the largest cation. An element that floats on water and reacts with it. An element that reacts with water to give a solution that can behave as an oxidising agent. An element whose nitrate gives a brown gas on thermal decomposition. Give the formula of the oxide of the most electronegative element. Several of these elements form more than one acidic oxide. Give the formulae of two such oxides formed by the same element. and The formulae and melting points of the fluorides of the elements in Period 3, Na to Cl, are given in the table. formula of fluoride NaF MgF2 Al F3 SiF4 PF5 SF6 Cl F5 m.p. / K Suggest the formulae of two fluorides that could possibly be ionic. What is the shape of the SF6 molecule? In the sequence of fluorides above, the oxidation number of the elements increases from NaF to SF6 and then falls at Cl F5. Attempts to make Cl F7 have failed but IF7 has been prepared. Suggest an explanation for the existence of IF7 and for the non-existence of Cl F7.
9701_s10_qp_21
THEORY
2010
Paper 2, Variant 1
View
The table below gives data for some of the oxides of Period 3 elements. oxide Na2O MgO Al 2O3 SiO2 P4O6 SO2 melting point /°C –75 bonding structure Complete the table by filling in the ‘bonding’ row by using only the words ‘ionic’ or ‘covalent’, the ‘structure’ row by using only the words ‘simple’ or ‘giant’. From the table of oxides above, suggest the formula of one oxide that is completely insoluble in water. Separate samples of Na2O and SO2 were added to water. For each oxide, write a balanced equation for its reaction with water and suggest a numerical value for the pH of the resulting solution. Na2O equation pH SO2 equation pH Construct a balanced equation for the reaction that occurs when a solution of Na2O in water reacts with a solution of SO2 in water. Separate samples of the oxides MgO and SiO2 are melted. Each molten sample is then tested to see whether or not it conducts electricity. Suggest what would be the results in each case. Explain your answers. MgO SiO2
9701_s10_qp_22
THEORY
2010
Paper 2, Variant 2
View
This question refers to the elements shown in the section of the Periodic Table below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr From this list of elements, identify in each case one element that has the property described. Give the symbol of the element. an element that sinks in cold water and reacts readily with it an element that forms an oxide that is a reducing agent the element that has the largest first ionisation energy the metal in Period 3 (Na to Ar) that has the smallest cation the element which has a giant molecular structure and forms an oxide which also has a giant molecular structure the element in Period 3 (Na to Ar) with the greatest electrical conductivity From the section of the Periodic Table above, identify two elements whose hydrides form hydrogen bonds between their molecules. and Use the elements in Period 3 (Na to Ar) in the section of the Periodic Table opposite to identify the oxidereferred to below. In each case, give the formula of the oxide. an oxide which has no reaction with water . two acidic oxides formed by the same element and an oxide which dissolves readily in water to give a strongly alkaline solution an oxide which is amphoteric
9701_s10_qp_23
THEORY
2010
Paper 2, Variant 3
View
Questions Discovered
288