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Form 4 chemistry questions and answers on metals
Brass is an alloy of zinc and copper. Give one use of brass.
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1.
(a) Explain why it is not advisable to use wood ash for cleaning aluminium utensils. (b) Duralumin is an alloy of aluminium. What is the advantage of using duralumin in place of aluminium for manufacture of aeroplane parts.
2.
The diagram below represents a set-up of an electronic cell that can be used in the production of aluminium. (a) On the diagram, label the anode. (b) Write the equation for the reaction at the anode. (c) Give a reason why the electrolytic process is not carried out below #950^0C#. (d) Give a reason why the production of aluminium is not carried out using reduction process. (e) Give two reasons why
3.
The extraction of aluminium from its ore takes place in two stages, purification stage and electrolysis stage. The diagram below shows the set up for the electrolysis stage. (a) (i) Name the ore from which aluminium extracted. (ii) Name one impurity which is removed at the purification stage
4.
(a) The diagram below shows the extraction of sodium metal using the Downs cell. Study it and answer the questions that follow: (i) Explain why in this process the sodium chloride is mixed with calcium chloride. (ii) Why is the anode made of graphite and not steel? (iii) State two properties of sodium metal that make it possible for it to be collected as shown in the diagram?
5.
Give one advantage and one disadvantage of using petrol containing tetraethyl lead in motor vehicles.
6.
Aluminum metal is a good conductor and is used for overhead cables. State any other two properties that make aluminium suitable for this use.
7.
(a) The flow chart below shows a sequence of reactions starting with iron. Study it and answer the questions that follow: (i) Name the reagent and state the condition for the reactions in step 1. (ii) Give the names of the following: (I) Solid S. (II) Solid V. (III) Solid T. (iii) Give reasons for the colour change in step 2. (iv) Write an ionic equation for the reaction which takes place in step
8.
The flow chart below illustrates the industrial extraction of lead metal. Study it and answer the questions that follow. (i) Name the ore that is commonly used in this process. (ii) Explain what takes place in the roasting furnace. (iii) Identify gas p. (iv) Write the equation for the main reaction that takes place in the smelting furnace. (v) What is the purpose of adding iron in the smelting
9.
When the oxide of element H was heated with powdered carbon, the mixture glowed and carbon (IV) oxide was formed. When the experiment was repeated using the oxide of element J, there was no apparent reaction. (a) Suggest one method that can be used to extract element J from its oxide. (b) Arrange the elements H, J and carbon in the order of their decreasing reactivity.
10.
Iron is extracted from its ore by the blast furnace process. (a) Name one ore from which iron is extracted. (b) One of the impurities in iron is removed in the form of calcium silicate. Write an equation for the reaction in which calcium silicate is produced.
11.
(a) Name one ore from which copper metal is extracted. (b) The flow chart below shows a sequence of reactions starting with copper. Study it and answer the questions that follow. (i) Identify: (I) Gas P. (II) Reagent Q. (III) Solid R. (ii) Write an equation for the reaction that takes place in step 5. (iii) State the observations made in steps 4 and 7.
12.
Brass is an alloy of zinc and copper. Give one use of brass.
13.
The basic raw material for extraction of aluminium is bauxite. (a) Name the method that is used to extract aluminium from bauxite. (b) Write the chemical formula of the major component of bauxite. (c) (i) Name two major impurities in bauxite. (ii) Explain how the impurities in bauxite are removed. (d) Cryolite is used in the extraction of aluminium from bauxite. State its function.
14.
Study the flow chart below and answer the questions that follow. (a) State the condition necessary for the reaction in step 2 to occur. (b) Name: (i) Gas D (ii) One use of zinc.
15.
In the industrial extraction of lead metal, the ore is first roasted in a furnace. The solid mixture obtained is then fed into another furnace together with coke, limestone and scrap iron. State the function of each of the following in this process: (a) Coke. (b) Limestone. (c) Scrap iron.
16.
(a) Below is a simplified diagram of the Downs cell used for the manufacture of sodium. Study it and answer the questions that follow. (i) What material is the anode made of? Give a reason. (ii) What precaution is taken to prevent chlorine and sodium from recombining? (iii) Write an ionic equation for the reaction in which chlorine gas is formed. (b) In the Downs process, (used for manufacture of
17.
(a) Explain why the metals magnesium and aluminium are good conductors of electricity. (b) Other than cost, give two reasons why aluminium is used for making electric cables while magnesium is not.
18.
The extraction of iron from its ores takes place in the blast furnace. Below is a simplified diagram of a blast furnace. Study it to answer the questions that follow. (a) Name: (i) One of the substances in the slag. (ii) Another iron ore material used in the blast furnace. (iii) One gas which is recycled. (b) Describe the processes which lead to the formation of iron in the blast furnace.
19.
The flow chart below shows a sequence of chemical reactions starting with copper. Study it and answer the questions that follow. (a) In step 1, excess 3M nitric (V) acid was added to 0.5g of copper powder. (i) State two observations which were made when the reactions was in progress. (ii) Explain why dilute hydrochloric acid cannot be used in step 1. (iii) (I) Write the equation for the reaction
20.
During the extraction of aluminium from its ores, the ore is first purified to obtain alumina. The flow chart below shows the stages in the extraction of aluminium from alumina. (a) Name: (i) Substance C1. (ii) Process D1. (b) Give two reasons why aluminium is used extensively in the making of cooking pans.
21.
Aluminium is both malleable and ductile. (a) What is meant by? (i) Malleable (ii) Ductile (b) State one use of aluminium based on: (i) Malleability (ii) Ductility
22.
(a) Name two ores from which copper is extracted. (b) During extraction of copper metal, the ore is subjected to froth flotation. Give a reason why this process is necessary. (c) Name one alloy of copper and state its use.
23.
One of the ores of copper has the formula, #CuFe_2#. (a) Describe how iron in the ore is removed during extraction of copper metal. (b) State two environmental problems associated with extraction of copper metal.
24.
(a) Name the raw material from which sodium is extracted. (b) Give a reason why sodium is extracted using electrolysis (c) Give two uses of sodium metal.
25.
The flow chart below shows steps used in the extraction of zinc from one of its ores. (a) Name the process that is used in step 2 to concentrate the ore. (b) Write an equation for the reaction which takes place in step 3. (c) Name one use of zinc other than galvanizing.
26.
Iron is obtained from haematite using a blast furnace shown in figure 5 below. (a) Four raw materials are required for the production of iron. Three of these are iron oxide, hot air and limestone. Give the name of fourth raw material. (b) Write an equation for the reaction in which carbon (IV) oxide is converted into carbon (II) oxide. (c) Explain why temperature in the region marked Y is higher
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