1. (d) AgNO3 solution and copper
2. (c) Applying coating of zinc
3. (a) Calcium
4. (c) Zinc is more reactive than tin
5. (a) Place the sample on an iron block. Strike with hammer. If the sample takes the shape of a sheet, it is a metal. If it breaks into pieces, it is a non-metal. Set up the arrangement by using a bulb, a battery, wires and switch. Insert the samples of metals and non-metals in the clips one by one and turn the switch on. If the bulb glows, the sample is a metal, if not, then the sample is non-metal.
(b)The above two methods can, in general, be used to distinguish between metals and non-metals.
6. Metal oxides which show both acidic as well as basic behavior are called amphoteric Such metal oxides react with both acids and bases.
Example: Aluminum oxide, zinc oxide
7. Magnesium and zinc metals displace hydrogen from dilute acids. Copper and silver do not displace hydrogen from dilute acids.
8. Impure metal M is made the anode, thin strips of pure metal M as cathode and a salt solution of metal M as electrolyte.
9. (a) Sulphur is a non-metal. Oxides of non-metals are acidic. In this case sulphur dioxide is produced which is acidic.
(i) No action of the gas
(ii) wet litmus paper will turn red.
(b) S(s) + O2 (g) → SO2 (g)
10. Rusting of iron can be prevented by
(i) By applying grease or paint.
(ii) By galvanizing
11. Acidic oxides are formed when non-metals combine with oxygen.
12. (a) These metals are un-reactive. They do not react with oxygen and other gases present in air and with moisture. Thus, their shine is maintained. That is why these metals are used to make jewellery.
(b) Reaction of sodium, potassium and lithium with oxygen is so violent that they catch fire. To prevent accidental fire, they are stored under kerosene oil.
(c) This is because aluminum is a good conductor of heat. Aluminum forms a layer of aluminum oxide at high temperature which is prevent the further corrosion.
(d) It is easier to reduce oxide than the carbonates and sulphide to the metals.
13. Copper, on keeping in air reacts with atmospheric carbon dioxide to form a green layer of copper carbonate. Copper carbonate reacts with citric acid present in lemon or tartaric acid present in tamarind to form soluble copper citrate or copper tartarate. The vessels are thus cleaned using water.
14. Metals and non-metals can be differentiated on the basis of following chemical properties.
15. Aqua regia, which is a mixture of 3 parts concentrated HCl and part of concentrated nitric acid dissolves gold. The man put the gold bangles in this solution. The outer dirty layer of gold bangles dissolved in aqua regia bring out the shining bangles. As the outer layer of bangles dissolved in aqua regia, the weight was reduced
16. Electrical conductivity of a metal is decreased when it is alloyed with another metal or non-metal. Thus, the electrical conductivity of steel is much less than that of pure . That is why copper is used to make hot water tanks and not steel.
17. (i) Mercury (ii) Sodium (iii) Silver (iv) Lead
18. A substance that can be beaten into thin sheets is said to be malleable. For example iron, copper etc.
A substance that can be drawn into wires is called ductile. For example gold, silver etc.
19. Sodium reacts so vigorously with oxygen that it catches fire when kept in the opens. Hence, to protect accidental fires, it is kept immersed in kerosene oil.
20. (i) 3Fe + 4H2O → Fe3O4 +H2
(ii) Ca + 2H2O → Ca(OH)2 + H2
2K + 2H2O → 2KOH + H2
21. (i) B is the most reactive metal
(ii)If B is added to a solution of copper (II) sulphate, displacement reaction will take place. Blue colour of copper sulphate will fade and red -brown copper will settle down.
(iii) The decreasing order of reactivity is:
22. Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
Fe + H2SO4 → FeSO4 +H2
23. As zinc is more reactive than iron, displacement reaction will take place
Zn + FeSO4 → ZnSO4 + Fe
24. (i) Electron-dot structure for sodium, oxygen and magnesium are
(iii) Ions present in Na2O are Na+ and O2-
O2- Ions present in MgO are Mg2+ and O2-
25. There are strong forces of attraction between oppositely charged ions in ionic compounds. Considerable amount of energy is required to break strong inter-ionic force of attraction. Therefore, they have high melting points.
26. (i) Minerals- the element or compounds which occur naturally in the earth crest are known as minerals.
(ii) Ores-Minerals from which metal can be extracted profitably and easily are called ores.
(iii) Gangue-Impurities such as soil and sand which are present in the minerals are called gangue.
27. Gold and Platinum
28. A metal is obtained from its oxide by the process of reduction.
29. Based on the activity series of metals, the displacement reactions will take place as below:
30. Metals which are placed at the bottom of activity series like silver, gold, platinum do not corrode easily.
31. An alloy is homogenous mixture of two or more metals or metal and non-metal. It is obtained by first melting primary metal and then dissolving the other element in it in definite proportion.