Exercise
Q1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
Ans.1(d)Agno3 solution and copper metal.
Q2. Which of the following methods is suitable for preventing an iron frying pan from
rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.
Ans.2 Applying a coating of zinc.
Q3. An element reacts with oxygen to give a compound with a high melting point. This
compound is also soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron.
Ans.3 Calcium
Q4. Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.
Ans.4 food can is coated with tin not to Zinc because Zinc is more reactive than tin.
Q5. You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and
non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and
non-metals.
Ans.5 (a) We can beat the samples with hammer and the sample which will be beaten into thin sheets then it will be the metal and the sample which will not malleable is Non metal.Wecan use the battery,bulb,wires and switch to set up a circuit with both samples, the sample through which electricity would conduct will be metal,and which will not Non metal.
(b)These above tests are useful for distinguishing between Metal and non metal.These tests are based on the physical properties and not on chemical properties.
Q6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Ans.6 Those oxides that act as both acidic as well as basic oxides. Such metal oxides react with both acid and base to produce salt and water are known as amphoteric oxides.
for example- Aluminium oxide, Zinc oxides etc.
Q7. Name two metals which will displace hydrogen from dilute acids, and two metals
which will not.
Ans.7 Metals that are more reactive than hydrogen (in reactivity series ) will displace hydrogen from dilute acids such as sodium and potassium.
Metal that are less reactive than hydrogen displace hydrogen from dilute acids.Such as- copper and silver.
Q8. In the electrolytic refining of a metal M, what would you take as the anode, the
cathode and the electrolyte?
Ans.8 In the electrolytic refining of metal M -
1. we would take impure metal M as anode.
2. We would take strip of pure metal M as cathode.
3. We would take solution of the salt solution of metal M as electrolyte.
Q9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas
evolved by inverting a test tube over it, as shown in figure below.
(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
Ans.9 (i) There will be no effect of evolved gas on dry litmus paper.
(ii) The evolved gas will turn the moist blue litmus to red because the gas produced is sulphur dioxide, because react with moisture to form sulphurous acid.
Q10. State two ways to prevent the rusting of iron.
Answer: There are two ways to protect iron from corrosion:
(i) By Isolation - In this method a thin layer of zinc is applied on iron and steel.
(ii) By painting - In this method, the iron object is painted so that its surface is not in direct contact with air and humidity.
Q11. What type of oxides are formed when non-metals combine with oxygen?
Answer: Non-metals combine with oxygen to form acidic oxides.
Q12. Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer: (a) Platinum, gold and silver are lustrous metals and do not corrode, so they are used for making jewellery.
(b) Sodium, potassium and lithium easily catch fire due to their high reactivity when left open in air. Hence it is stored inside the oil.
(c) Aluminum utensils do not corrosive easily, so they are good conductors of heat.
(d) It is a much easier process to separate metals from their oxides, so carbonate and sulphide ores are converted into oxides in the extraction process.
Q13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer: A substance like lemon or tamarind contains acid, this acid is effective in cleaning the impure substance of copper, due to which the luster of copper utensils remains.
Q14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer: Chemical properties of metals:
(i) Metals form basic oxides.
(ii) Metals are reducing agents.
(iii) Metals displace hydrogen from water.
Chemical Properties of Nonmetals:
(i) Non-metals form acidic or neutral oxides.
(ii) Non-metals are oxidising.
(iii) Non-metals are not able to displace hydrogen from water.
Q15. A man went door to door posing as a goldsmith. He promised to bring back the
glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold
bangles to him which he dipped in a particular solution. The bangles sparkled
like new but their weight was reduced drastically. The lady was upset but after a
futile argument the man beat a hasty retreat. Can you play the detective to find
out the nature of the solution he had used?
Answer: The man used "Aqua Regia" solution to dissolve the woman's gold and the weight was reduced. It contains concentrated HCl and concentration HNO3 in a 3:1 ratio.
Q16. Give reasons why copper is used to make hot water tanks and not steel (an alloy
of iron).
Answer: Copper is a good conductor of heat and it does not react with hot water, on the contrary iron reacts with hot water.
