2000-01 / MTAu / Form 5 / Half-yearly Exam / Chemistry Paper I / Page.1
Hoi Ping Chamber of Commerce Secondary School
Half-yearly Examination (2000-01)
Date : 12th January, 2001
Name : ______Form 5 _____ Class no. : ______
Chemistry Paper I
8.30 am - 10.00 am (1 ½ hours)
This paper must be answered in English
- There are TWO sections in this paper, Section A and Section B.
- Answer ALL questions in Sections A and B.
- When answering questions in Section A, you are NOT required to start each question on a new page.
SECTION A (Answer ALL questions.)(46 marks)
- Liquid wastes discharged from some factories are acidic and need to be neutralized before discharging into the sea. A certain factory used slaked lime (calcium hydroxide) to neutralize its liquid waste, which consisted of 0.5 M hydrochloric acid, discharging at a rate of 20 dm3 per minute.
(a)Why are the liquid wastes neutralized before discharging into the sea ?
(b)Write an equation for the reaction between hydrochloric acid and slaked lime.
(c)Calculate the mass of slaked lime required per minute to neutralize the acid present in the liquid wastes.
(d)Although slaked lime is cheaper, factories nowadays use sodium carbonate instead of slaked lime to neutralize their acidic liquid wastes. Suggest a reason.
(Relative atomic masses : H = 1.0 ; O = 16.0 ; Ca = 40.0)
(6 marks)
- For each of the following experiments, state the expected observation and write a relevant chemical equation.
(a)Dilute nitric acid is added to zinc carbonate powder in a beaker.
(b)Burn pure ethanol with plenty supply of air.
(c)A mixture of propane and bromine vapour is exposed to diffused sunlight.
(6 marks)
- Some of the ingredients present in a certain brand of cheese sticks are as follows :
Benzoic acid, corn meal, cheese, monosodium glutamate (MSG),
Sunset yellow (E110), vegetable oil
Which of the above ingredients are food additives ? Suggest ONE function for each of the food additives.
(6 marks)
- Long chain molecules obtained from the fractional distillation of crude oil can be converted to smaller molecules by the process of cracking. One example is illustrated by the equation below :
C10H22 A + B
Where A is a saturated hydrocarbon containing 7 carbon atoms, and
B is an unsaturated hydrocarbon.
(a)Why is cracking important in the petroleum industry ?
(b)Write the molecular formula of A.
(c)
(i)Explain the term “unsaturated hydrocarbon”.
(ii)Write the structural formula of B.
(iii)Give one use of B.
(d)Suggest a chemical test to distinguish B from A, and write an appropriate equation.
(e)Predict whether A or B would have the higher boiling point and explain your answer.
(9 mark)
5.The table below describes some reactions of liquid ethanol :
EXPERIMENT / RESULT- Ethanol is heated with acidified potassium permanganate solution.
- A mixture of ethanol and substance X is heated with concentrated sulphuric acid.
- Ethanol is heated and the vapour passed over heated broken porcelain.
(i)Name X.
Write an ionic equation for the reaction of X with sodium carbonate solution.
(ii)Write an equation for the formation of Y.
Suggest TWO functions of the concentrated sulphuric acid in experiment 2.
(iii)Draw a diagram to indicate how experiment 3 can be carried out in the laboratory, and how gas Z should be collected.
(iv)Z can undergo addition polymerization to form a polymer.
(1)Name the polymer formed and draw the repeating unit.
(2)State one household article that can be made from the polymer.
(10 marks)
For question 6, candidates are required to give paragraph-length answers. 3 of the marks of this question will be awarded for effective communication of knowledge in Chemistry.
6.Describe how large crystals of ammonium nitrate can be prepared from an aqueous solution of ammonia in a school laboratory.
(9 marks)
End of Section A
SECTION B (Answer ALL questions.)(54 marks)
7.
(a)The following diagram represents the industrial manufacture of sulphuric acid :
(i)Name the industrial process shown in the above diagram.
(ii)
(1)Write an equation to represent the reaction in the catalytic conversion chamber.
(2)Suggest a suitable catalyst in the catalytic chamber.
(3)The catalytic effect of the catalyst gradually diminishes after some time. Give a reason for this and hence suggest how its catalytic effect could be prolonged.
(4)Instead of dissolving sulphur trioxide directly in water to form sulphuric acid, sulphur trioxide is absorbed by concentrated sulphuric acid, followed by dilution with water. Give TWO advantages of this method.
(5)The sulphuric acid obtained by this industrial process contains 98% by mass of sulphuric acid and has a density of 1.84 g cm-3. Calculate the volume of the acid required for dilution of 500 cm3 of 0.10 M sulphuric acid.
(Relative atomic masses : H = 1.0 ; O = 16.0 ; S = 32.0)
(iii)A company has decided to build an industrial plant in Hong Kong for the production of sulphuric acid. Is this a good decision ? Give TWO reasons to explain your answer.
(12 marks)
(b)The diagram below shows a longitudinal section of a fire extinguisher. When the extinguisher is being used, solution X is allowed to mixed with the sodium hydrogencarbonate solution and a reaction immediately occurs. A jet of aqueous solution will then be forced out of the extinguisher.
(i)Suggest what solution X may be.
(ii)
(1)Write an ionic equation for the reaction between solution X and the sodium hydrogencarbonate solution.
(2)Explain why a jet of aqueous solution is forced out of the extinguisher.
(iii)The diagram below shows a “fire triangle”.
(1) Complete the “fire triangle” by writing a suitable word for “Y”.
(2)Using the concept of “fire triangle”, give TWO reasons why the fire extinguisher mentioned previously can be used to put out a fire.
(iv)In the Mass Transit Railway, bromochlorofluoromethane (BCF) fire extinguisher shown above, is used to put out electrical fires.
Suggest ONE advantage and ONE disadvantage of using a BCF fire extinguisher to put out electrical fires.
(8 marks)
8.
(a)Crude oil is a mixture consisting mainly of alkanes. Fractional distillation of crude oil gives different petroleum fractions. The table below lists the length of carbon chain of the alkanes in some of the fractions.
Fraction / Length of carbon chainPetrol / naphtha / C5– C10
Kerosene / C11– C18
Diesel / C18– C25
X / C20– C34
(i)Describe the principle underlying the fractional distillation of crude oil.
(ii)
(1)Explain why the global demand for petrol is greater than that for kerosene.
(2)Cracking kerosene can produce petrol. State the conditions required for the cracking process.
(iii)In Hong Kong, naphtha instead of coal is used to manufacture town gas.
(1)State ONE advantage of using naphtha instead of coal to manufacture town gas.
(You are NOT required to consider the price of the materials.)
(2)Explain why an additive with a foul smell is added to town gas before it is delivered to the consumers.
(iv)Give ONE use of fraction X in cars.
(9 marks)
(b)A mixture of air and ammonia is slowly drawn through the apparatus as shown in the diagram below. A reaction occurs when the platinum gauze is heated.
(i)The heat source can be removed shortly after the reaction has started. Suggest an explanation for this.
(ii)Suggest how the gaseous mixture can be drawn through the apparatus.
(iii)What would be observed in flask B ? Explain your answer.
(iv)
(1)Write an balanced equation for the reaction which occurs in the combustion tube.
(2)State the importance of this reaction in industry.
(8 marks)
9.
(a)The structural formulae of three common detergents are as follows :
Detergent I :
Detergent II :
Detergent III :
(i)Which one is a “soapless” detergent ?
(ii)Name two starting materials for preparing detergent I in the laboratory.
(iii)What would be observed if seawater were shaken in a test-tube with a small quantity of an aqueous solution of
(1)detergent I, and
(2)detergent II ?
(iv)Draw the part of the anion of detergent I which would mix well with water.
(v)Of the above three detergents, detergent III causes the greatest pollution problem when discharged into rivers or the sea. Suggest a reason for this.
(vi)
(1)One possible approach to remove oil patches from the sea in coastal areas is to spray some detergent over them. Explain briefly the action of the detergent in this process.
(2)Detergent should not be used to remove oil patches near fish farms. Explain why this is so.
(8 marks)
(b)Polyvinyl chloride (PVC) is a plastic which has a wide range of uses.
(i) Write the chemical equation for the formation of PVC from its monomers.
(ii)Plastic products made of PVC may vary greatly in rigidity.
(1)Give ONE flexible product made of PVC.
(2)Give ONE rigid product made of PVC.
(3)Explain whether PVC is suitable for making electric sockets or not.
(iii)Incineration of PVC wastes produces hydrogen chloride which causes air pollution.
(1)State ONE harmful effect of the discharge of hydrogen chloride into the atmosphere.
(2)Suggest how hydrogen chloride can be removed from incinerator flue gas prior to its discharge to the atmosphere.
(3)Suppose that all the chlorine in PVC is converted to hydrogen chloride upon incineration. Calculate the volume of hydrogen chloride produced, measured at room temperature and pressure, when a plastic waste containing 1000 kg of PVC is incinerated.
(You may assume that no other chlorine-containing compounds are present in the waste.)
(Relative atomic masses : H = 1.0, C = 12.0, Cl = 35.5;
molar volume of gas at room temperature and pressure = 24.0 dm3)
(9 marks)