Ch 3 Metals & Non metals Class 10 Important Questions | NCERT Science Chapter-3
- 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.
Answer
(a)
(i) There will be no action on dry litmus paper.
(ii) The colour of litmus paper will turn red because sulphur is a non-metal and the oxides of non-metal are acidic in nature.
(b) S (s) + O2(g) → SO2 (g)
2.State two ways to prevent the rusting of iron.
Answer
Two ways to prevent the rusting of iron are:
→ Oiling, greasing, or painting: By applying oil, grease, or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.
→ Galvanisation:An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and moisture. Hence, rusting is prevented.
3. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer
| Metal | Non-metal |
| Metals are electropositive. | Non-metals are electronegative. |
| Oxides of metal are basic in nature. | Oxides of non-metals are acidic in nature. |
| Metals displace hydrogen from dilute acids. | They can’t replace hydrogen from dilute acids. |
| Metals form chlorides which are electrovalent or ionic compounds. | Non-metals form chlorides which are covalent compounds. |
| They react with water to form oxides and hydroxides. Some metals react with cold water, some with hot water, and some with steam. | They do not react with water. |
4. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?
Answer
(i) The representation of elements with valence electrons as dots around the elements is referred to as electron-dot structure for elements.
(ii)
(iii) The ions present in Na2O are Na+ and O2– ions and in MgO are Mg2+ and O2– ions.
5. (a) Write electron dot diagram for chlorine (At No. 17) and calcium (At No. 20).
Show the formation of calcium chloride by transfer of electrons.
(b) Identify the nature of above compound’and explain three physical properties of such compound. Answer.
(b) It is ionic compound.
Physical properties
1.It is hard and solid.
2.It has high melting and boiling point.
3.It soluble in water.
6. (a) An ore on treatment with dilute hydrochloric acid produces brisk effervesces. What type of ore is this? What steps will be required to obtain metal from the enriched ore. ,
(b) Copper coin is kept immersed in silver nitrate solution for some time. What change will take place in coin and colour of the solution ? Write balanced chemical equation of the reaction involved.
Answer.
(a) Carbonate ore:
(i) Calcination: Carbonate ore is heated in limited supply of air and oxide is obtained, e.g.
(b) Copper, being more reactive than silver will displace silver from silver nitrate solution and there will be deposition of silver on copper coin. The colour of solution will turn to blue.
7.(a) Define activity series of metals. Arrange the metals gold, copper, iron and magnesium in order of their increase in reactivity.
(b) What will you observe when:
(i) Some zinc pieces are put in copper sulphate solution.
(ii) Some silver pieces are put into green coloured ferrous sulphate solution.
Answer.
(a) The series of metals in which metals are arranged in decreasing order of their reactivity.
Au < Cu < Fe < Mg is increasing order of reactivity.
(b) (i) The blue solution will become colourless and reddish brown copper metal will be deposited.
Reaction will not take place because Ag’ is less reactive than iron.
8.Give reason for the following:
(a) Aluminium oxide is considered as an amphoteric oxide.
(b) Ionic compounds conduct electricity in molten state.
Answer.
(a) It is because it reacts with acids as well as bases to produce salts and water.’Al’ is less electropositive metal. So, it forms amphoteric oxide which can react with acid as well as base.
(b) Ionic compounds can conduct electricity in molten state because ions ’ become free to move in molten state.
9.Write balanced equations for the reaction of:
(i) aluminium when heated in air. Write the name of the product.
(ii) iron with steam. Name the product obtained.
(iii) calcium with water. Why does calcium start floating in water?
Answer.
The bubbles of hydrogen stick to the surface of metal that is why it floats.
10. What is meant by ‘rusting’? With labelled diagrams, describe an activity to find out the conditions under which iron rusts.
Answer. The process in which iron reacts with oxygen in the presence of moisture to form reddish brown coating of hydrated ferric oxide [Iron (III) oxide].Fe2O3 xH20
Activity:
(i) Take three boiling tubes A, B and C.
(ii) Pour some water in test tube A Put iron nails in it and cork it.
(iii) Pour boiled distilled water in another test tube B and put iron nails in it. Add 1 ml of ojl over it such that oil flo’ats over it and prevents the air from entering.
(iv) Take some iron nails in test tube C and put some anhydrous calcium chloride in it and cork it.
(v) Leave all the three test tubes for one day and then observe.
Observation: Iron nails get rusted in test tube A because both air and water are present in it. Iron nails do not get rusted in B because there is water but no air. In C, rusting will not take place because there is neither air nor water. Conclusion: Iron gets rusted in the presence of air and water.
Important Link
Quick Revision Notes: Metal & Non-Metal
NCERT Solution : Metal & Non-Metal
MCQs: Metal & Non-Metal
