Test o Level

1Topic 05 Energy From Chemicals

1. Which of the following changes is endothermic?A H(g) + Cl(g) HCl(g) B H2O(g) 2H(g) + O(g)C H2O(l) H2O(s) D 2H2(g) + O2(g) 2H2O(l)

s04/q182 .The reaction C2H4 + 3O2 2CO2 + 2H2O is exothermic becauseA more bonds are broken than are formed.B more bonds are formed than are broken.C the energy needed to break the bonds is greater than that released on forming new bonds.D the energy needed to break the bonds is less than that released on forming new bonds.

s05/q123. Which reaction profile shows the fastest exothermic reaction?

s05/q134. The equation below shows an exothermic reaction.

Mg(s) + 2HCl(aq) MgCl 2(aq) + H2(g)Which statement about this exothermic reaction is not correct?A Magnesium chloride is soluble in water.B Magnesium is above hydrogen in the reactivity series.C One mole of magnesium produces one mole of hydrogen gas.D The total energy of the products is greater than that of the reactants.

s06/q155. The diagram shows the energy profile for a chemical reaction.

What is the correct description of the reaction?sign of ΔH overall energy

changesign of EA

ABCD

–+++

exothermicendothermicendothermicexothermic

–+–+

s06/q16

6. The energy diagram for the reaction between sodium hydroxide and hydrochloric acid is shown.What can be deduced from the diagram?A Heat is needed to start the

reaction.B The products contain less energy than the reactants.C The reaction is rapid.D The OH– ions have more energy than the H+ ions.

s07/q14

7. The diagram shows an energy profile diagram for a chemical reaction. Which energy change is the activation energy for the catalysed reaction?

w03/q158. The formation of hydrogen iodide from hydrogen and iodine is an endothermic reaction.

H H + I I H I + H I What may be deduced from this information?A The number of bonds broken is greater than the number of bonds formed.B The formation of H – I bonds absorbs energy.C The products possess less energy than the reactants.D The total energy change in bond formation is less than that in bond breaking.

w03/q169. The table shows the energy released by the complete combustion of some compounds used as fuels.

compound

formula Mr ΔH in kJ / mol

methaneethanolpropaneheptane

CH4

C2H5OHC3H8

C7H16

164644

100

–880–1380–2200–4800

Which fuel produces the most energy when 1 g of the compound is Completely burned? A ethanol B heptane C methane D propane

w04/q1810. The diagram shows the reaction pathway for a reaction without a catalyst.

Which diagram shows the pathway resulting from the addition of a catalyst to the reaction?

O/AS/A2/SATII/SSEULTIMATE CHEMISTRY PREPARATION WITH ZAFAR IQBAL CH.(03334227604)


w04/q20

11. The energy profile diagram below is for a reaction P + Q R + S.

Which statement is correct?A The activation energy of the reaction is (H3 − H1).B The activation energy of the reaction is (H3 − H2).C ΔH is (H1 − H2).D ΔH is (H1 − H3).

w05/q1312. On combustion, which fuel never produces pollutants? A diesel B hydrogen C methane D petrol

w06/q14

13. The energy profile diagrams show how adding a substance X to a reaction mixture changes the reaction pathway.Which change occurs when X is added to the reaction mixture?A The rate of reaction decreases. B The rate of reaction increases.C The reaction becomes less exothermic.D The reaction becomes more exothermic.

w06/q1614. In which process is energy released?A electrolysis of water to form hydrogen and oxygenB forming a hydrogen molecule from two hydrogen atomsC fractional distillation of crude oilD photosynthesis

w07/q16



Q1. Hydrogen reacts with chlorine to make hydrogen chloride. The reaction is exothermic.The reaction can be represented by the equation below.H –– H + Cl –– Cl H –– Cl + H –– Cl H = –184 kJ/mol(a) A mixture of 2.5 g of hydrogen and 142 g of chlorine is allowed to react.(i) Which gas, hydrogen or chlorine, is in excess?Explain your answer.

..............................................................................................................

..............................................................................................................

..............................................................................................................(ii) Calculate the energy released when 2.5 g of hydrogen reacts completely with chlorine gas.

[3](b) Explain why the reaction is exothermic, in terms of the energy changes that take place during bond breaking and bond making.

..............................................................................................................

..............................................................................................................

..........................................................................................................[3](d) Nitrogen reacts with oxygen to form nitrogen(II) oxide. The energy profile diagram for the reaction is shown below.

(i) Is the reaction exothermic or endothermic?Explain your answer.

..............................................................................................................

..............................................................................................................

..............................................................................................................(ii) Label on the diagram the activation energy for the reaction. [2]

s02/q2Q2. Methane, CH4, is used as a fuel. The complete combustion of methane can be represented by the equation below.

(a) Explain why this reaction is exothermic in terms of the energy changes that take place during bond breaking and bond making.

..............................................................................................................

..........................................................................................................[3](b) Calculate the energy released when 4.0 g of methane is completely combusted.

..........................................................................................................

..........................................................................................................[2]

(c) Draw the energy profile diagram for the complete combustion of methane. Label on the diagram the activation energy and the enthalpy change.

[3]s03/q10

Q.3. Aqueous hydrogen peroxide is used to sterilise contact lenses.At room temperature aqueous hydrogen peroxide decomposes very slowly to form water and oxygen.The decomposition can be represented by the equation below.

(a) Explain why this reaction is exothermic in terms of the energy changes that take place during bond breaking and bond making.

..........................................................................................................

..........................................................................................................

..........................................................................................................[2](b) Draw the energy profile diagram for the decomposition of hydrogen peroxide. Label on the diagram the activation energy and the enthalpy change.

[3]s04/q7



Q.4. Oxides of nitrogen are atmospheric pollutants. Nitrogen monoxide, NO, is formed in an internal combustion engine when nitrogen and oxygen react together.

N2(g) + O2(g) 2NO(g)The diagram shows the energy profile for this reaction.

(a) Identify the energy changes X and Z.

..........................................................................................................

..........................................................................................................[2](b) The reaction between nitrogen and oxygen is endothermic.(i) Explain how you can tell from the diagram that the reaction is endothermic.

..........................................................................................................

..........................................................................................................[1]

(ii) Explain, using ideas about bond breaking and bond making, why the overall reaction is endothermic.

..........................................................................................................

..........................................................................................................[3]s07/q10

Q.5. In the future, fuel cells may be used to power cars.In a fuel cell, the overall reaction is represented by the equation

2H2(g) + O2(g) 2H2O(l)(a) This is the energy profile diagram for the reaction between hydrogen and oxygen.

(i) Label on the diagram the activation energy of the reaction.(ii) The fuel cell contains a catalyst. Draw a second curve on the diagram to show the energy profile for the catalysed reaction.(iii) Explain why this reaction is exothermic in terms of bond breaking and bond forming.

..............................................................................................................

..............................................................................................................

........................................................................................……….......[5]w02/q5

Q.6. Petroleum is a complex mixture of hydrocarbons. Petroleum is a source of many useful fuels.(a) What is meant by the term hydrocarbon?

..............................................................................................................

..........................................................................................................[1](b) Petroleum is separated by fractional distillation.(i) Complete the following table about the fractions obtained from petroleum.

fraction usepetrol (gasoline) fuel for carsparaffin (kerosene)

diesel fuel for diesel enginesBitumen

(ii) Name one other fraction obtained from petroleum.

..........................................................................................................[3](c) Fractional distillation of petroleum does not produce sufficient of some fractions to match demand.Cracking is used to convert large hydrocarbon molecules into smaller molecules that are more in demand.A hydrocarbon of molecular formula C12H26 is cracked.(i) Suggest the formula of one alkane that may be produced.

..............................................................................................................(ii) Suggest the formula of one alkene that may be produced.

..............................................................................................................s03/q3



Q.7 Petroleum is a mixture of hydrocarbons. In an oil refinery it is separated into fractions by fractional distillation. The diagram shows a fractionating column and some of the fractions obtained from petroleum.

(a) State the physical property on which the separation depends.

..........................................................................................................[1](b) (i) State one use for the naphtha fraction.

..............................................................................................................(ii) State one use for the bitumen fraction.

..........................................................................................................[2](d) Describe the importance of cracking in the oil refining process.

..............................................................................................................

..............................................................................................................

..........................................................................................................[2]s05/q4

Q.8. Liquid Petroleum Gas (LPG) and ethanol can be used as fuels for cars instead of petrol. LPG contains mainly propane. This table shows some information about propane and ethanol.

name formulaboiling

point / °Cphysicalstate at

r.t.p.

enthalpychange of

combustion/ kJ per

mole

method of manufacture

ethanol C2H5OH 78.................

– 1367fermentation of sugar cane

propane.................

– 42.................

– 2220.......................

......................of crude oil

(a) Complete the table by filling in the boxes. [4](b) When 1 kg propane burns, 50 450 kJ of energy are given out.Show by calculation, using data from the table, that ethanol gives out less energy per kg than propane.

[3](c) Give two advantages of using ethanol rather than propane as a fuel for cars.

..............................................................................................................

......................................................................................................... [2](d) In a car engine, a spark plug ignites a mixture of air and ethanol. The spark is needed because the combustion of ethanol needs activation energy. Complete the energy level diagram below for the combustion of ethanol. Show the names of the products and label the activation energy for the reaction.

[3]w03/q3

Q.9. This diagram shows a fractionating column for the separation of crude oil.

The following fractions leave the column.fraction number of carbon

atomsboiling range /

°Cnaptha 7 – 14 90 – 150



paraffindiesel oil

9 – 1615 – 25

150 – 240220 – 250

(a) Which fractions leave the column at each of the points A, B and C?

..........................................................................................................[1](b) Explain how the fractionating column separates the crude oil mixture.

..............................................................................................................

..............................................................................................................

..........................................................................................................

..........................................................................................................[3]

(c) Octane, C8H18, is a hydrocarbon in petrol. Hexadecane, C16H34, is one of the hydrocarbons in ship fuel.(i) Show by calculation that hexadecane contains a higher percentage of carbon by mass than octane.

..............................................................................................................This is the equation for the complete combustion of octane.

2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(g)(ii) Write an equation for the complete combustion of hexadecane.

..............................................................................................................(iii) Use the equations to explain why hexadecane burns with a smokier flame than octane.

..............................................................................................................

..............................................................................................................

..........................................................................................................[5](d) Name two fuels, suitable for cars, which do not come from crude oil.

..........................................................................................................[1][Total: 10 marks]

w04/q8Q.10. Methane, CH4, is the major constituent of natural gas.(a) A very small quantity of methane is present in the atmosphere.State another source of this gas.

..........................................................................................................[1](b) State a use of methane.

..........................................................................................................[1](c) In the presence of light methane reacts with chlorine.

CH4 + Cl2 CH3Cl + HCl H = –99.5 kJ

Draw an energy profile diagram for this reaction. Show:• the reactants and products, • the activation energy,• the enthalpy change.

[3]w06/q6


Test o Level

Documents

Transcript of Test o Level