9701_w09_qp_22 - revisedeck

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Examiner s Use The elements carbon and silicon are both in Group IV of the Periodic Table. Carbon is the second most abundant element by mass in the human body and silicon is the second most common element in the Earth’s crust. Carbon and silicon each form an oxide of general formula XO2. At room temperature, CO2 is a gas while SiO2 is a solid with a high melting point. Briefly explain, in terms of the chemical bonds and intermolecular forces present in each compound, why CO2 is a gas and SiO2 is a solid at room temperature. Draw a simple diagram to show the structure of SiO2. Your diagram should contain at least two silicon atoms and show clearly how many bonds each atom forms. For Examiner’s Use CO2 does not behave as an ideal gas. State the basic assumptions of the kinetic theory as applied to an ideal gas. Suggest one reason why CO2 does not behave as an ideal gas. Carbon exists in a number of forms, one of which is a conductor of electricity and one of which is a non-conductor of electricity. Silicon is the main component of most semi-conductors. Graphite is the form of carbon that is a conductor of electricity. Give a simple explanation for this property. When carbon and silicon(oxide are heated together at about 2000 °C, silicon carbide, SiC, is formed. Silicon carbide is a hard material which is widely used as an abrasive and in ceramics. Construct an equation for the reaction of carbon and silicon(oxide. SiC has a similar structure to one of the common forms of carbon. Which form is this? Give a reason for your answer. form reason

4. States of matter → 4.2. Bonding and structure

9. The Periodic Table: chemical periodicity → 9.1. Periodicity of physical properties of the elements in Period 3

14. Hydrocarbons → 14.2. Alkenes

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For Examiner’s Use The elements of the third period of the Periodic Table form chlorides of general formula ECl x where E represents the element. These chlorides show a variation in oxidation number from sodium to sulfur. Use the information given to complete the table below. formula of chloride NaCl MgCl 2 Al Cl 3 SiCl 4 PCl 3 SCl 2 oxidation number of element in the chloride By considering the electron configurations of the elements, explain the variation in oxidation number in the chlorides from Na to Al and from Si to S. Na to Al Si to S Sodium hydride, NaH, is a colourless crystalline solid which melts at 800 °C and has the same crystal structure as sodium chloride which has a melting point of 808 °C. When molten sodium chloride is electrolysed using graphite electrodes, a shiny deposit, D, forms on the cathode and a greenish-yellow gas is evolved from the anode. When molten sodium hydride is electrolysed, under suitable conditions using graphite electrodes, the same shiny deposit D is formed on the cathode and a colourless gas, G, is evolved from the anode. Describe with the aid of a diagram the bonding in a sodium chloride crystal. Suggest the type of bonding that is present in sodium hydride. What is the oxidation number of hydrogen in sodium hydride? For Examiner’s Use Draw a ‘dot-and-cross’ diagram for sodium hydride. Show outer electrons only. The metals magnesium and aluminium form hydrides with formulae MgH2 and Al H3. The non-metals phosphorus and sulfur form hydrides with formulae PH3 and H2S. By considering their positions in the Periodic Table, suggest oxidation numbers for these four elements in their hydrides. compound MgH2 Al H3 PH3 H2S oxidation number of element in the hydride At room temperature, the chlorides of sodium, magnesium and aluminium are all solids which dissolve in water. The hydrides of sodium, magnesium and aluminium are also solids which react with water with the rapid evolution of the same colourless gas G in each case. What is the pH of the solutions formed when separate samples of sodium chloride, magnesium chloride, and aluminium chloride are dissolved in water? chloride sodium magnesium aluminium pH Suggest an equation for the reaction between sodium hydride and water. Suggest a value for the pH of the solution formed in . At room temperature, the chlorides of silicon, phosphorus and sulfur are all low melting point solids or low boiling point liquids that can be seen to react with water. Suggest what type of bonding is present in sulfur dichloride, SCl 2. Write a balanced equation for the reaction between the chloride of silicon, SiCl 4, and water.

9. The Periodic Table: chemical periodicity → 9.2. Periodicity of chemical properties of the elements in Period 3

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For Examiner’s Use One method of making 1-bromobutane in the laboratory is described below. Stage 1 Place 35 g of powdered sodium bromide, 30 cm3 of water, and 25 cm3 (20 g) of butan-1-ol, in a 250 cm3 two necked flask fitted with a tap funnel and reflux condenser. Stage 2 Concentrated sulfuric acid (25 cm3) is then placed in the tap funnel and added drop by drop to the reagents in the flask, keeping the contents well shaken and cooled occasionally in an ice-water bath. The overall reaction may be considered to take place in two stages. In the first stage the inorganic reagents react together to form HBr. In the second stage, the organic reagent reacts with the HBr that is formed in the first stage. Write an equation for each of these stages. stage I stage II In this preparation, by using the amounts given above, one of the reagents, sodium bromide or butan-1-ol, will be present in an excess. Use your equations in and the data above to determine, by calculation, which reagent is in an excess. In a laboratory preparation of 1-bromobutane, when 15.4 g of butan-1-ol was used, 22.5 g of 1-bromobutane was obtained after purification. Calculate the yield of 1-bromobutane as a percentage of the theoretical maximum yield. For Examiner’s Use When the concentrated sulfuric acid is added to the reaction mixture (stage 2), unless the temperature is controlled carefully, the acid may react with either of the original reactants (sodium bromide or butan-1-ol) to give at least two by-products, one of which is inorganic and the other organic. What inorganic and organic by-products may be formed? In each case, identify one by-product and state the role of the concentrated sulfuric acid in the formation of this by-product. inorganic by-product role of conc. H2SO4 organic by-product role of conc. H2SO4

15. Halogen compounds → 15.1. Halogenoalkanes

14. Hydrocarbons → 14.2. Alkenes

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For Examiner’s Use Complete the following reaction scheme which starts with 1-bromobutane. In each empty box, write the structural formula of the organic compound that would be formed. CH3CH2CH2CH2Br K2Cr2O7/H+ heat under reflux conc. KMnO4/H+ heat under reflux NaOHNaOH in ethanol heat under reflux heat under reflux W Y X Z For Examiner’s Use One of the compounds W, X, Y or Z can be polymerised. Identify this compound by its letter. Draw a section of the polymer chain formed by this compound. Show two repeat units.

15. Halogen compounds → 15.1. Halogenoalkanes

13. An introduction to AS Level organic chemistry → 13.1. Formulas, functional groups and the naming of organic compounds

21. Organic synthesis → 21.1. Organic synthesis

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For Examiner’s Use The fermentation of starch or molasses using the bacterium Clostridium acetobutylicum, produces a mixture of propanone and butan-1-ol. Give the reagentand state what would be observed when one test is carried out to confirm the presence of propanone in a mixture of propanone and butan-1-ol. reagentobservation What will be observed when a small piece of sodium metal is dropped into a dry sample of butan -1-ol? Write an equation for the reaction that takes place. observation equation The molecular formula C5H12O represents a number of alcohols. Three alcohols with molecular formula C5H12O are straight chain pentanols. Draw the following formulae. the structural formula of pentan-1-ol the displayed formula of pentan-2-ol the skeletal formula of pentan-3-ol For Examiner’s Use When one of the three pentanols in is dehydrated, alkenes with two different structural formulae are formed. Identify this alcohol and give the structural formula of each alkene. name of alcohol alkene 1 alkene 2 A number of alcohols with molecular formula C5H12O are branched chain compounds and may be considered as derivatives of butanol or propanol with alkyl side chains. Draw the structural formula of the derivative of propanol that has the molecular formula C5H12O. Draw the structural formula of the organic compound that will be present when the derivative of propanol you have given in is heated under reflux with acidified potassium dichromate(.

16. Hydroxy compounds → 16.1. Alcohols

13. An introduction to AS Level organic chemistry → 13.1. Formulas, functional groups and the naming of organic compounds

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