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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 XO_2.
At room temperature, CO_2 is a gas while SiO_2 is a solid with a high melting point.
(a) Briefly explain, in terms of the chemical bonds and intermolecular forces present in each compound, why CO_2 is a gas and SiO_2 is a solid at room temperature.
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(b) Draw a simple diagram to show the structure of SiO_2. Your diagram should contain at least two silicon atoms and show clearly how many bonds each atom forms. [2]
CO_2 does not behave as an ideal gas.
(c) (i) State the basic assumptions of the kinetic theory as applied to an ideal gas.
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(ii) Suggest one reason why CO_2 does not behave as an ideal gas.
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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.
(d) Graphite is the form of carbon that is a conductor of electricity. Give a simple explanation for this property.
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When carbon and silicon(IV) 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.
(e) (i) Construct an equation for the reaction of carbon and silicon(IV) oxide.
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(ii) 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 ............................................................................................................................... [2]
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(a) (i) Use the information given to complete the table below.
[Table_1]
formula of chloride | NaCl | MgCl_2 | AlCl_3 | SiCl_4 | PCl_3 | SCl_2
oxidation number of element in the chloride
(ii) 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 .............................................................................................................
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Si to S .................................................................................................................
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(b) (i) Describe with the aid of a diagram the bonding in a sodium chloride crystal.
(ii) Suggest the type of bonding that is present in sodium hydride.
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(iii) What is the oxidation number of hydrogen in sodium hydride?
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(iv) Draw a 'dot-and-cross' diagram for sodium hydride. Show outer electrons only.
(v) The metals magnesium and aluminium form hydrides with formulae MgH_2 and AlH_3. The non-metals phosphorus and sulfur form hydrides with formulae PH_3 and H_2S. By considering their positions in the Periodic Table, suggest oxidation numbers for these four elements in their hydrides.
[Table_2]
compound | MgH_2 | AlH_3 | PH_3 | H_2S
oxidation number of element in the hydride
(c) (i) What is the pH of the solutions formed when separate samples of sodium chloride, magnesium chloride, and aluminium chloride are dissolved in water?
[Table_3]
chloride | sodium | magnesium | aluminium
pH
(ii) Suggest an equation for the reaction between sodium hydride and water.
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(iii) Suggest a value for the pH of the solution formed in (ii).
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(d) (i) Suggest what type of bonding is present in sulfur dichloride, SCl_2.
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(ii) Write a balanced equation for the reaction between the chloride of silicon, SiCl_4, and water.
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One method of making 1-bromobutane in the laboratory is described below.
[Table_1]
(a) 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 ............................................................................................................................. [2]
(b) 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 (a) and the data above to determine, by calculation, which reagent is in an excess. [2]
(c) 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. [2]
(d) 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. $H_2SO_4$ .....................................................................................
organic by-product .............................
role of conc. $H_2SO_4$ ..................................................................................... [4]
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(a) 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.
(b) One of the compounds W, X, Y or Z can be polymerised.
(i) Identify this compound by its letter.
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(ii) Draw a section of the polymer chain formed by this compound. Show two repeat units.
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The fermentation of starch or molasses using the bacterium Clostridium acetobutylicum, produces a mixture of propanone and butan-1-ol.
(a) Give the reagent(s) and 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. [2]
(b) 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. [2]
The molecular formula $C_5H_{12}O$ represents a number of alcohols. Three alcohols with molecular formula $C_5H_{12}O$ are straight chain pentanols.
(c) Draw the following formulae.
(i) the $\textit{structural}$ formula of pentan-1-ol
(ii) the $\textit{displayed}$ formula of pentan-2-ol
(iii) the $\textit{skeletal}$ formula of pentan-3-ol [3]
When one of the three pentanols in (c) is dehydrated, alkenes with $\textbf{two}$ different structural formulae are formed.
(d) Identify this alcohol and give the structural formula of $\textbf{each}$ alkene. [3]
A number of alcohols with molecular formula $C_5H_{12}O$ are branched chain compounds and may be considered as derivatives of butanol or propanol with alkyl side chains.
(e) (i) Draw the structural formula of the $\textit{derivative of propanol}$ that has the molecular formula $C_5H_{12}O$.
(ii) Draw the structural formula of the organic compound that will be present when the derivative of propanol you have given in (i) is heated under reflux with acidified potassium dichromate(VI). [2]
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