Q.1. Give an example of a metal which
(a) is a liquid at room temperature.
(b) can be easily cut with a knife.
(c) is the best conductor of heat.
(d) is a poor conductor of heat.
(a) Metal that exists in a liquid state at room temperature is mercury.
(b) Metal that can be easily cut with a knife is sodium.
(c) Metal that is the best conductor of heat is silver.
(d) Metal that is a poor conductor of heat is lead.
Q.2. Explain the meanings of Malleable and Ductile.
Q.1. Why is sodium kept immersed in kerosene oil?
Q.2. Write equations for the reactions of
(a) iron with steam
(b) calcium with water
(c) potassium with water.
(a) 3Fe (s) + 4H2O (g) → Fe3O4 (aq) + 4H2 (g)
(b) Ca(s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) Heat
(c) 2K(s) + 2H2O (l) → 2KOH (aq) + H2 (g) Heat
Q.3. Samples of four metals A, B, C, and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
Use the table above to answer the following questions about metals A, B, C, and D.
(a) Which is the most reactive metal?
(b) What would you observe if B is added to a solution of copper (II) sulfate?
(c) Arrange the metals A, B, C, and D in the order of decreasing reactivity.
Q.4. Which gas is produced when diluted hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Ans. When dilute hydrochloric acid is added to a reactive metal; hydrogen gas is evolved.
The reaction between iron and H2S04 is:
Q.5. What would you observe when zinc is added to a solution of iron (II) sulfate? Write the chemical reaction that takes place.
Ans. Zinc is more reactive than iron. Therefore, if zinc is added to a solution of iron (II) sulfate, then it would displace iron from the solution.
Q.1. (a) Write the electron-dot structures for sodium, oxygen, and magnesium.
(b) Show the formation of Na2O and MgO by the transfer of electrons.
(c) What are the ions present in these compounds?
(b) Formation of Na2O and MgO
Na → Na+ + e-
O +2e- → O-
Mg → Mg2++ 2e-
O + 2e- → O2-
(c) The ions present are Na+, O2- and Mg2+ in compounds sodium oxide (Na2O) and magnesium oxide (MgO).
Q.2. Why do ionic compounds have high melting points?
Ans. Ionic compounds have high melting points because of the strong force of attraction between the oppositely charged ions. High energy is required to break the metallic bonds between these ions.
Q.1. Define the following terms.
Q.2. Name two metals which are found in nature in the free state.
Ans. The metals at the bottom of the reactivity series are mostly found in a free state.
Example: Gold, Silver, and Platinum
Q.3. What chemical process is used for obtaining a metal from its oxide?
Ans. The chemical process used for obtaining a metal from its oxide is reduction.
There are mainly three different methods of reduction:
(i) By heating
(ii) By using carbon
(iii) By using aluminium, calcium, sodium, etc., as reducing agents.
Q.1. Metallic oxides of zinc, magnesium, and copper were heated with the following metals.
In which cases will you find displacement reactions taking place?
Q.2. Which metals do not corrode easily?
Ans. The more reactive a metal is, more likely it is to be corroded. Therefore, less reactive metals are less likely to get corroded. This is why gold plating provides high resistance to corrosion.
Example: Gold, Platinum.
Q.3. What are alloys?
Ans. Alloys are homogeneous mixtures of two or more elements. The elements could be two metals or a metal and a non-metal. An alloy is formed by first melting the metal and then dissolving the other elements in it.
Example: Steel is an alloy of iron and carbon.
Q.1. 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. This is decided on the basis of the activity series of metal. A metal higher on the activity series can displace a metal lower on the activity series from its salt solution. Thus
(a) No displacement
(b) No displacement
(c) No displacement
(d) Displacement reaction takes place
► Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq)+ 2Ag(s)
because copper is more reactive than Ag.
Q.2. 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
Q.3. 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
Ans. (a) Calcium oxide has a high melting point as it is ionic in nature and is soluble in water.
Q.4. 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. (c) Zinc is more reactive than tin; that is why tin is used.
Food cans are coated with tin and not with zinc because zinc is above the tin in reactivity series means more reactive than tin and can react with food elements preserved in it.
Q.5. 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.
Q.6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Q.7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Ans. Zn and Al will displace hydrogen from dilute acids because they are more reactive than hydrogen, whereas Cu and Ag cannot displace hydrogen from dilute acids because they are less reactive than hydrogen.
► Zn(s) + 2HCl(dil) → ZnCl2(aq) + H2(g)
► 2Al(s) + 6HCl(dil) → 2AlCl3(aq) + 3H2(g)
Q.8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode, and the electrolyte?
Ans. Impure metal acts as an anode, and pure metal acts as a cathode. Soluble salt of metal acts as an electrolyte.
Q.9. 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 the 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.
(i) There will be no action on dry litmus paper.
(ii) The colour of litmus paper will turn red because sulfur is a non-metal, and the oxides of non-metal are acidic in nature.
(b) Chemical Equation for the reaction taking place.
S + O2 → SO2
(Sulphur) Sulphur dioxide
SO2 + H2O → H2SO3
Q.10. State two ways to prevent the rusting of iron.
Ans. Two ways to prevent the rusting of iron are:
Q.11. What type of oxides are formed when non-metals combine with oxygen?
Ans: Mostly acidic oxides are formed when non-metal combines with oxygen.
Q.12. 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 sulfide ores are usually converted into oxides during the process of extraction.
(a) Platinum, gold, and silver are used to make jewellery because they are:
(b) Sodium, potassium, and lithium are:
(c) Though aluminium is a highly reactive metal, it is resistant to corrosion.
This is because:
(d) Carbonate and sulfide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulfides.
Q.13. 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.
Q.14. Differentiate between metal and non-metal on the basis of their chemical properties.
Q.15. 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?
Q.16. Give reasons why copper is used to making hot water tanks and not steel (an alloy of iron).
Ans: Electrical conductivity of a metal is decreased when it is alloyed with another metal or non-metal. Thus, the electrical conductivity of steel (which is an alloy) is much less than that of pure copper. That is why copper is used to making hot water tanks and not steel.