CHAPTER-METALS AND NONMETALS

CLASS-X CHEMISTRY

CORE QUESTION-ANSWERS

Q1 Name the metal which is most abundant in earths crust.

Ans Aluminium is the most abundant in earths crust and is present to the extent of 8.1 percent by mass.

Q2 What is the chemical formula of the rust?

Ans Rust is hydrated ferric oxide and its chemical formula is Fe2O3..H2O.

Q3 Write the chemical formulae of the main ore of aluminium and iron.

Ans The main ore of aluminium is bauxite(Al2O3.2H2O) and haematite (Fe2O3. )

Q4 What is the difference between the normal and lewis symbol of an element?

Ans In the normal symbol, the valence electrons are not shown while in the lewis symbol they are shown either dots or crosses. For example ,ordinary symbol of sodium is Na and its lewis symbol is Na

Q5 Why do metals behave as reducing agents?

Ans The reducing character of an element is expressed in terms of electron releasing tendency .Since metals can easily lose electrons ,they behave as reducing agents. For example

M(s) Mn+ (aq) +ne-

Q6 Why are metals generally lustrous?

Ans The surface of a metal has a shinning appearance. This is known as lusture. When light falls on the surface of metals, electrons present on the surface absorb photons of light which are energy carrier. These electrons get excited and start

vibrating. During the vibration they release energy as light. That is why metals are generally lustrous.

Q7 Oxides of the metals which are high in activity series are not reduced by carbon .How will you account for it?

Ans Metals which lie high in the reactivity series like Na ,K, Ca, Mg are reactive in nature. The oxides of these metals are extremely stable. Moreover, the metals present in these oxides are strong reducing agent. As a result these oxides can not be reduced to the metallic form by heating with carbon (coke).For examples

CaO +C(s) no reaction

Q8 You are provided with three metals :sodium ,magnesium and copper .Using only water as the reactant, how will you identify them?

Ans (a) The metal which reacts violently with cold water and catches fire is sodium.

(b) The metal which evolve hydrogen gas with hot water is magnesium.

(c) The metal which does not reacts with water even on strong heating is copper.

Q9 An element E combines with oxygen to form an oxide E2O which is good conductor of electricity. Give the following information.

(i) How many valence electrons will be present in the valence shell of the element E.

(ii) Write the formula of the compound formed when E reacts with chlorine.

Ans (i) From the formula E2O it is clear that valency of an element E is 1 ,hence E has got one valence electron.

(ii)We know that chlorine is monovalent . Since the valency of E is 1. This means the formula of the chloride of E will be ECl.

Q10 (i) Name a metal which does not stick to glass.

(ii)Name a non-metal which is a good conductor of electricity.

(iii) Name the metal which is commonly used in thermit welding. (iv) What is deposited at cathode: a pure or impure metal. (v) What is the nature of (a) ZnO (b) CO

Ans (i) mercury

(ii) graphite

(iii) aluminium

(iv) a pure metal

(v)(a) amphoteric (b) neutral

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