14.1. Alkanes
A subsection of Chemistry, 9701, through 14. Hydrocarbons
Listing 10 of 122 questions
Petrol and diesel fuel are both used in internal combustion engines. Petrol may be regarded as having the formula C9H20 and diesel fuel as having the formula C14H30. To which class of compounds do these two hydrocarbons belong? Write a balanced equation for the complete combustion of petrol. When petrol or diesel fuel are used in internal combustion engines, several different products of the incomplete combustion of the fuel may be formed. Name two of these products that do not contain hydrogen. and Choose one of these and state a hazard it causes. product hazard Write a balanced equation for the formation of one of the products in from diesel fuel. Defi ne the term standard enthalpy change of combustion. A 1.00 cm3 sample of C14H30 was completely burnt in air. The heat produced raised the temperature of 250 g of water by 34.6 °C. Assume no heat losses occurred during this experiment. The density of C14H30 is 0.763 g cm–3. Use relevant data from the Data Booklet to calculate the amount of heat released in this experiment. Use the data above and your answer to to calculate the energy produced by the combustion of 1 mol of C14H30.
9701_w13_qp_23
THEORY
2013
Paper 2, Variant 3
View
Heptane, C7H16, is an undesirable component of petrol as it burns explosively causing ‘knocking’ in an engine. There are nine structural isomers with the formula C7H16, only two of which contain chiral centres. Explain the meanings of the terms structural isomers and chiral. structural isomers chiral Give the structures and names of the two structural isomers of C7H16 which contain a chiral centre. Write an equation for the complete combustion of heptane. Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant. Incomplete combustion can also lead to emission of unburnt hydrocarbons. State one environmental consequence of this. The reaction of heptane with chlorine in the presence of UV light produces a wide variety of products. Formation of the monochloroheptanes can be represented by the following equation. C7H16 + Cl 2 → C7H15Cl + HCl Name the mechanism of the reaction between heptane and chlorine in the presence of UV light. Describe this mechanism, using suitable equations and including the names of each stage in the process.
9701_w15_qp_21
THEORY
2015
Paper 2, Variant 1
View
Heptane, C7H16, is an undesirable component of petrol as it burns explosively causing ‘knocking’ in an engine. There are nine structural isomers with the formula C7H16, only two of which contain chiral centres. Explain the meanings of the terms structural isomers and chiral. structural isomers chiral Give the structures and names of the two structural isomers of C7H16 which contain a chiral centre. Write an equation for the complete combustion of heptane. Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant. Incomplete combustion can also lead to emission of unburnt hydrocarbons. State one environmental consequence of this. The reaction of heptane with chlorine in the presence of UV light produces a wide variety of products. Formation of the monochloroheptanes can be represented by the following equation. C7H16 + Cl 2 → C7H15Cl + HCl Name the mechanism of the reaction between heptane and chlorine in the presence of UV light. Describe this mechanism, using suitable equations and including the names of each stage in the process.
9701_w15_qp_23
THEORY
2015
Paper 2, Variant 3
View
Crude oil is a natural source of hydrocarbons that are used as fuels. Hydrocarbons with low relative molecular mass, Mr, are used as fuels in industry, in the home and for transport. There is a high demand for the hydrocarbons with low Mr. Name the process by which long-chain hydrocarbons are broken down into shorter-chain hydrocarbons. Give one reason why hydrocarbons with low Mr are suitable for use as fuels. Incomplete combustion of hydrocarbons can release carbon monoxide, CO, into the atmosphere. Write an equation for the formation of CO from the incomplete combustion of butene, C4H8. Identify an analytical technique that can be used to monitor the levels of CO in the atmosphere. Outline how this analytical technique may be used to monitor the levels of CO. Thiophene, C4H4S, is an organic compound that is found as a contaminant in crude oil. Construct the equation for the complete combustion of thiophene, C4H4S. Include state symbols in your answer. A student carries out an experiment to determine the enthalpy change of combustion of C4H4S. Explain the meaning of the term enthalpy change of combustion. The student uses the following apparatus in the experiment. thermometer water copper container fuel burner containing C4H4Smass of water in copper container / g initial temperature of water / °C 18.5 highest temperature of water / °C 37.5 Calculate the heat energy released, in J, by the reaction. Assume that 4.18 J of heat energy changes the temperature of 1.0 cm3 of water by 1.0 °C. Assume no heat is lost to the surroundings.  heat energy released = J  The student used 0.63 g of C4H4Sin the experiment. Calculate the enthalpy change of combustion of thiophene, ΔHc(C4H4S). Include a sign in your answer. ΔHc(C4H4S) = kJ mol–1  
9701_w19_qp_21
THEORY
2019
Paper 2, Variant 1
View
Questions Discovered
122