Chemistry Essay Example

11-15 jet fuel Gas oil (diesel) 15-19 central heating fuel Mineral oil 20-30 lubrication Fuel oil 30-40 Wax 41-50 candles Bitumen over 50 road surfacing

(a) Complete the table above by writing in the empty boxes

(b) Give one structural formula in each case for the following components of crude oil:

(I) the isomer of CACHE with the lowest boiling point a saturated compound with molecular formula SOCIO

(c) Give a molecular formula for each of the following components of crude oil:

(I) the alkaline which, on cracking, forms, as the only products, two moles of ethane and one mole of butane per mole of alkaline. The straight chain alkaline found in the petrol fraction which contains the lowest percentage by mass of hydrogen.

Refer to the table at the start of the question to educe your answer.

(2) (d) Write an equation for the complete combustion of the alkaline which requires 1 1 moles of oxygen per mole of alkaline for complete combustion.

(2) (Total 9 marks)

5. There are eight structural isomers with the molecular formula CACHE BRB. Four of these are classed as primary, three as secondary and one as tertiary.

The graphical formula of one of the secondary compounds, isomer A, is shown below. Isomer A (I) Give the name of isomer A. (it) Explain what is meant by the term structural isomers. (ill) Draw the graphical formula of the tertiary compound with molecular formula Chubb, isomer B.

(1) Total 5 marks)

6. (a) Central heating fuel is obtained by distillation of crude oil. An alkaline present in central heating fuel contains 16 carbon atoms per molecule. When a molecule of this alkaline is cracked, propane is formed.

I)

Name the crude oil fraction used as central heating fuel. (it) Write an equation for the cracking of the 16-carbon alkaline to form octane, propane and ethane as the only products commercial use of propane.

Give one important (b) A catalytic converter in the exhaust system of a car contains a ceramic honeycomb covered with a thin coating of the catalyst. When hot gases containing nitrogen monoxide and unborn octane are passed over the catalyst, they react to form nitrogen, carbon dioxide and water.

(I) Explain why the catalyst is coated on a honeycomb. (it) Write an equation for the reaction of octane with nitrogen monoxide to form nitrogen, carbon dioxide and water.

(4) 7. There are five structural isomers of the molecular formula SOCIO which are alikeness.

The graphical formulae of two of these isomers are given. Isomer 1 Isomer 2 Draw the graphical formulae of two of the remaining alkaline structural isomers. (Total 2 marks)

8. (a) Petrol engines in cars produce a number of pollutants which can be removed y catalytic converters.

Discuss this statement, indicating what the pollutants are, how they arise and how they are removed as efficiently as possible in a catalytic converter. Write equations for any reactions you discuss.

(11) (b) Petrol is obtained, not only by fractional distillation of crude oil, but also by cracking of hydrocarbons from heavy fractions.

State why hydrocarbons from heavy fractions are cracked and explain why these hydrocarbons are less easy to ignite than those in petrol. (4) (Total 15 marks)

9. Ethane and other important hydrocarbons can be produced industrially from decade, CHICHI.

Name the process involved and give the name of the mechanism occurring. Write two equations for

reactions in which ethane is formed from decade by this process. Explain the economic importance of the process. (Total 8 marks)

10. There are four structural isomers of molecular formula Chubb. The structural formulae of two of these isomers are given below. CH3CH2CH2CH2Br (it) Name isomer 1. (Total 3 marks)

11 .Catalytic cracking and thermal cracking of petroleum fractions produce different types of products, both of which are valuable.

Discuss the catalytic cracking of a petroleum fraction. In your answer you should tote the conditions used and the type of mechanism involved. Identify the products formed and state their uses. Give two economic reasons for the catalytic cracking of alkaline. (Total 9 marks) (a) Four members to the homologous series to alikeness are ethane, propane, but-I-NNE and pent-I-NNE.

(I) Give one structural feature of the compounds that makes them members of the homologous series of alikeness.

(1) (ii) State the trend in the boiling points from ethane to pent-I-NNE. 1) (iii) Give the name and draw the graphical formula of an alkaline that is an isomer of but-I-NNE and that has a different carbon skeleton. Total 4 marks)

13. (a) Gas oil (diesel), kerosene (paraffin), mineral oil (lubricating oil) and petrol (gasoline) are four of the five fractions obtained by the fractional distillation of crude oil within the temperature range 40-400 co. Identify the missing fraction and state the order in which the five fractions are removed as the fractionating column is ascended.

Give two reasons why the fractions collect at different levels in the fractionating column.

(4) (b) Thermal cracking of large hydrocarbon molecules is used to produce alikeness. State the type of mechanism involved in this process.

Write an equation for

the Herman cracking of CA HUH in which ethane and propane are produced in a 3:2 molar ratio together with one other product.

(3) (c) Write equations, where appropriate, to illustrate your answers to the questions below.

(I) Explain why it is desirable that none of the sulfur-containing impurities naturally found in crude oil are present in petroleum fractions.

(ii) The pollutant gas NO is found in the exhaust gases from petrol engines. Explain why NO is formed in petrol engines but is not readily formed when petrol burns in the open air.

(iii) The pollutant gas CO is also found in the exhaust gases from petrol engines. Explain how CO and NO are removed from the exhaust gases and why the removal of each of them is desirable.

(10) (Total 17 marks)

14. A) Gas oil (diesel), kerosene (paraffin), mineral oil (lubricating oil) and petrol (c)Write equations, where appropriate, to illustrate your answers to the questions Explain why it is desirable that none to the sulfur-containing impurities naturally found in crude oil are present in petroleum fractions. (it) The pollutant gas NO is found in the exhaust gases from petrol engines. Explain why NO is formed in petrol engines but is not readily formed when petrol burns in the open air. Iii) The pollutant gas CO is also found in the exhaust gases from petrol engines.

Explain how CO and NO are removed from the exhaust gases and why the removal of each of them is desirable.

(10) 15. (a) Crude oil is separated into fractions by fractional distillation. Outline how different fractions are obtained by this process.

(3) (b) The table below gives details of the supply of, and demand

for, some crude oil fractions. I) Use the data given above to explain why catalytic cracking of crude oil fractions is commercially important.

Give the two main types of product obtained by catalytic cracking.

(4) c) Name a catalyst used in catalytic cracking. State the type of mechanism involved and outline the industrial conditions used in the process.

(4) (Total 11 marks)

16. Many hydrocarbon compounds burn readily in air.

(I) Write an equation to show the complete combustion of CLC AH (it) One of the gaseous products of the incomplete combustion of methane in gas fires is known to be poisonous.

Identify this product and write an equation for the reaction in which it is formed from methane. (Total 4 marks) 17. The alkaline form an homologous series of hydrocarbons.

The first four straight-chain alkaline are shown below.

Methane CHI ethane CHICHI European CHICHI butane CH3CH2CH2CH3

(a) (I) State what is meant by the term hydrocarbon. (it) Give the general formula for the alkaline. (iii) Give the molecular formula for hexane, the sixth member of the series.

(3) (b) Each homologous series has its own general formula.

State two other characteristics of an homologous series.

(2) (c) Branched-chain structural isomers are possible for alkaline which have more than three carbon atoms. (I) State what is meant by the term structural isomers. (d) Name the two isomers of hexane shown below.

Give the structures of two other branched-chain isomers of hexane.

A hydrocarbon, W, contains 92. % carbon by mass. The relative molecular mass of W is 78.0 (I) Calculate the empirical formula of W. Calculate the molecular formula of W. 18. (a) Butane, SOCIO, is a hydrocarbon which is used as a fuel. (I) Explain what

is meant by the term hydrocarbon. (it) Explain what is meant by the term fuel. (iii) Write an equation for the complete combustion of butane. (iv) Write an equation for the incomplete combustion of butane to produce carbon monoxide and water. (v) Under what conditions would you expect incomplete combustion to occur?

(5) (b) Ethane can be cracked in the presence of a catalyst to produce ethane and hydrogen. I) Write an equation for this reaction. (it) Give a suitable catalyst for this reaction.

(ill) State one reason why cracking is important. 19. Four isomers with the formula CHOUGH are given below. Isomer Name CH3CH2CH2CH20H butane-l-OLL 2-anthropometry-2-OLL (I) Complete the naming of the isomers in the table above. (it) Name the type of isomerism shown by these four isomers. (Total 3 marks) 20.

(a) Crude oil is composed mainly of alkaline, which are saturated hydrocarbons. (I) State what is meant by the term hydrocarbon. (it) State what is meant by the term saturated, as applied to a hydrocarbon.

(2) b) Crude oil can be separated into the fractions listed in the table below.

Name of fraction Number of carbon atoms ALP (liquefied petroleum gas) 4-?12 Mineral oil (lubricating oil) 20 - 30 (I) Name the process used to obtain these fractions from crude oil.

Complete the table by naming the missing fraction.

(c)Some of the naphtha fraction is thermally cracked to produce more useful products. (I) Give the molecular formula of an alkaline with ten carbon atoms. (it) Write an equation to illustrate the thermal cracking of one molecule of tetrahedral, CHICHI, in which the products are ethane and propane, in the ratio of 2:1, and one there product. (iii)

Name the mechanism involved in thermal cracking.

21. The burning of fossil fuels can produce atmospheric pollutants.

A) The combustion of petrol in an internal combustion engine can lead to the formation of carbon monoxide, CO, and nitrogen monoxide, NO. (I) Write an equation for the incomplete combustion of octane, CACHE, to produce CO and water only. (it) State one essential condition for the formation of NO in an engine.

Write an equation for the reaction in which NO is formed.

(3) (b) All new petrol-engines cars must be fitted with a catalytic converter. I) Name one of the metals used as a catalyst in a catalytic converter. (it) Write an equation to show how CO and NO react with each other in a catalytic converter.

(2) (c) State why sulfur dioxide gas is sometimes found in the exhaust gases of petrol- engines cars.

Give one adverse effect of sulfur dioxide on the environment.

(2) (Total 7 marks) 22. (a) (I) Name the process used to separate petroleum into fractions. (it) Give the molecular formula for an alkaline with nine carbon atoms. (iii) Write an equation for the complete combustion of the alkaline CLC IHA (v) Write an equation for the incomplete combustion of CLC 1 H2O to produce carbon and water only.

(4) (b) Alikeness can be produced by cracking the naphtha fraction obtained from petroleum.

(I) Write an equation for the thermal cracking of one molecule of CIO H2O to give one molecule of propane and one molecule of an alkaline only. (it) Draw the structure of the chain isomer of but-I -NNE. C) The alkaline and the alikeness are examples of homologous series of compounds. One feature of

an homologous series is the gradual change in physical properties as the relative molecular mass increases. State two other general features of an homologous series of compounds. 2)

23. Petroleum is separated into fractions by fractional distillation. The petrol fraction (CA to CA) is burned in internal combustion engines and the naphtha fraction (CA to CA) is cracked.

(a) Petroleum is separated into attractions when it is heated and the vapor mixture is passed into a fractionating column. (I) Explain what is meant by the term fraction as applied to fractional distillation. Ii) State a property of the molecules in petroleum which allows the mixture to be separated into fractions.

(iii)Describe the temperature gradient in the column.

(b) The fractions from petroleum contain alkaline hydrocarbons. I) Write an equation for the incomplete combustion of the alkaline CACHE to produce carbon monoxide and water only. One isomer of CACHE is Draw the structure of this isomer.

(2) (c) State one economic reason for the cracking of petroleum fractions. (1) (d) (I) Give the type of reactive intermediate formed during catalytic cracking. (ii) Identify a catalyst used in catalytic cracking.

(e) (I) Give the type of reactive intermediate formed during thermal cracking.

State how this reactive intermediate is formed. (ii) Identify the different type of hydrocarbon produced in a high percentage by the Herman cracking of alkaline.

(3) 24. The fractions obtained from petroleum contain saturated hydrocarbons that belong to the homologous series of alkaline.

(a) Any homologous series can be represented by a general formula. (I) State two other characteristics of homologous series. (it) Name the process which is used to obtain the fractions from petroleum.

(iii) State what is meant by the term saturated,

as applied to hydrocarbons.

(4) (b) Decade has the molecular formula CHICHI (I) State what is meant by the term molecular formula. It) Give the molecular formula of the alkaline which contains 14 carbon atoms. Ill) Write an equation for the incomplete combustion of decade, CLC OHIO, to produce carbon and water only. (3) (c)When petrol is burned in an internal combustion engine, some nitrogen monoxide, NO, is formed.

This pollutant is removed from the exhaust gases by means of a reaction in a catalytic converter. (I) Write an equation for the reaction between nitrogen and oxygen to form nitrogen monoxide. (it) Identify a catalyst used in a catalytic converter. (iii) Write an equation to show how nitrogen monoxide is removed from the exhaust gases as they pass through a catalytic converter.