Time : 2 Hours (Model Answer Paper) Max. Marks : 40

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1 08 00 MT MT - SCIENCE & TECHNOLOGY - I (7) - SEMI PRELIM - II : PAPER - Time : Hours (Model Answer Paper) Max. Marks : 40 A.. (A) Solve the ollowing questions : () When the angle o incidence is more than critical angle Total internal reection takes place. () Ozone layer () True (4) False - Metals are electropositive and non-metals are electronegative. (5) kg : Mass o the Earth : : m : Radius o the Earth. A.. (B) Choose the correct alternative and rewrite the sentences : () Oily ood kept out or ew days gives a bad taste and a bad smell because o Rancidity. () When a ray o light strikes a glass slab at an angle o 50º with the normal to the surace o the slab, the angle o incidence is 50º. () As the height o the object rom the surace o the Earth increases, value o g becomes less. (4) Mg, Ca, Sr triad does not ollow Dobereiner s law o triad. (5) Inside water, an air bubble behaves like a concave lens. A.. Solve the ollowing questions : (Any 5) () When sodium carbonate solution is added to calcium chloride solution, solid calcium carbonate and aqueous solution o sodium chloride is ormed. It is a double displacement reaction. Sodium Carbonate Calcium chloride Calcium carbonate Sodium chloride () Given: Object distance (u) 60 cm Image distance (v) 0 cm To nd: Focal length ()?

2 / MT PAPER Formulae: Solution: v u v u cm Since, is ve, Lens is concave i.e. diverging lens. () Alkali metals and Alkaline earth metals : Alkali metals (i) In the Modern Periodic Table, Group elements are alkali metals. (ii) Atoms o these elements have one electron in the valence shell. (iii) They are monovalent. (iv) Their oxides and hydroxides dissolve readily in water. (i) (ii) Alkaline earth metals In the Modern Periodic Table, Group elements are alkaline earth metals. Atoms o these elements have two electrons in their valence shell. (iii) They are divalent. (iv) Their oxides and hydroxides dissolve slightly in water.

3 / MT PAPER (4) Given: n.6 w vac v vac 0 8 m/s To nd: v w? Formula: w n vac v vac v w Solution:.6 08 v w v w 08.6 v w. 0 8 m/s The velocity o light in water is. 0 8 m/s (5) (i) Air, heat, light aect the quality o edible oil, which deteriorate through oxidation (rancidity). (ii) The oxidation process is greatly enhanced when edible oils are stored in containers that are not air tight and in areas where oil is exposed to air, heat and light. (iii) Hence, it is recommended to use air tight containers or storing oil or long time, to prevent it rom getting oxidised. (6) Name o the element Symbol Atomic Number Electronic Conguration Carbon C 6 4 Lithium Li Fluorine F 9 7 Nitrogen N 7 5 Oxygen O 8 6 K L All the elements given above belong to second period. While going rom let to right in a period, Non-metallic character increases. The tendency o an element to orm anion or the electronegativity is the non-metallic character o an element. As Fluorine is present in extreme right o period, it will also possess highest non-metallic character and also Fluorine has 7 electrons in its outermost shell, that means electron less to complete its octet.

4 4 / MT PAPER (7) As we gradually go towards the centre o the Earth, the mass o Earth under consideration goes on decreasing. We know, g GM R At the centre o the Earth, the mass o earth under consideration is zero, Hence,g at the centre o the earth becomes zero. A.. Solve the ollowing questions : (Any 5) () A F B F O F F B Image position: Beyond F Nature: Real, inverted and magnied. A () Given : Power o lens (P).5 D To nd : Focal length ()? Formula : P (m) Solution: P (m) P m Since is +ve, lens used is convex. Hence deect is Hypermetropia (arsightedness)

5 5 / MT PAPER () (i) I a planet revolves around the Sun in a circular orbit, then the centripetal orce exerted on it by the Sun is F mv r where, m - mass o the planet v - velocity and r - radius o its orbit. (ii) Distance travelled in one revolution by the planet Circumerence Time period o revolution T speed distance time v πr T F mv r m πr T F r F 4mπ r T F 4mπ r T F 4mπ r F but r r r T... 4mπ kr 4mπ k is constant T r k or r T...(i)...[rom(i)] k...(ii)...[rom(ii)] r F r This is how Newton proved the inverse square law o gravity using Kepler s law. (4) Types o reaction with reerence to oxygen and hydrogen are oxidation reaction and reduction reaction. Oxidation reaction: The chemical reaction in which a reactant combines with oxygen or loses hydrogen to orm the product is called Oxidation reaction. e.g. Mg + O MgO

6 6 / MT PAPER Here O combines with magnesium (Mg) to orm magnesium oxide (MgO) MgH Mg + H Here MgH loses hydrogen. Reduction reaction: The chemical reaction in which a reactant combines with hydrogen or loses oxygen to orm product is called reduction reaction. e.g. C + H CH 4 Here carbon combines with hydrogen and orms compound CH 4 (Methane). HgO Hg + O Here Mercuric oxide loses oxygen to orm mercury. (5) (i) Centre o curvature o a lens : The centres o the spheres whose parts orm suraces o the lenses are called centres o curvature. (ii) Principal axis o a lens : The imaginary line passing through the centre o curvatures is called principal axis. (iii) Optical centre o a lens : The imaginary point on the lens through which the light ray passes undeviated is called optical centre. (6) Neutralisation Reaction : The reaction in which an acid and a base react together to orm salt and water is called Neutralisation Reaction. For example : HCl (aq) + NaOH (aq) NaCl (aq) + H O (l) Water Hydrochloric acid Sodium hydroxide Sodium chloride (7) (i) No xed position could be given to hydrogen which resembles alkali metals and halogens in the periodic table. (ii) Isotopes have dierent atomic masses but same chemical properties. Based on chemical properties, they were to be placed in same group, while based on atomic masses, they were used to be placed in dierent groups. Hence, there was no denitive place or isotopes. (iii) In certain places, elements with higher atomic mass were placed beore elements o lower mass e.g. Co (At. Mass 58.9) was placed beore Ni (At. Mass 58.7) (iv) Some elements with dierent properties were placed in same group. e.g. (Mn) Manganese was placed with halogens which totally dier in properties.

7 A.4. Solve the ollowing questions : (Any ) 7 / MT PAPER () (a) Step : Write the equation given. SO + H S S + H O...() Count the number o atoms o each element in product and reactants. Elements in reactants in products S O H Step : It is seen rom the above table, number o atoms on both sides are not same. It means that equation () need to be balanced. Step : We will start with oxygen. On product side we need atoms o oxygen, hence coecient or H O. Now the equation will be SO + H S S + H O...() Again count the number o atoms o elements on both the sides. Elements in reactants in products S O H 4 Still the equation is unbalanced. To balance sulphur and hydrogen atoms on reactant side, write coecient or H S SO + H S S + H O...() Again count the number o atoms on both the sides. Elements in reactants in products S O H 4 4 Now i we will count no. o atoms o hydrogen and oxygen, they are equal. But no. o atoms o sulphur is not balanced. Now there are atoms o sulphur on reactant side, whereas on product sides it is only one atom. Hence, we write coecient or sulphur on R.H.S. Now the equations becomes. SO + H S S + H O...(4) Again count no, o atoms in equation (4)

8 8 / MT PAPER Elements in reactants in products S O H 4 4 It means equation (4) is balanced. (b) Comparative study o blocks s-block p-block d-block -block No. o shells incomplete/ valence electrons Outermost shell incomplete ( or valence electrons). Outermost shell incomplete except zero group elements that have completely lled shells Last two shells incomplete. Last three shells incomplete. ( to 8 valence electrons). Position Group, Group and Hydrogen Group to Group 7 and zero group Group to Group Lanthanides series and actinides series placed separately at the bottom o periodic table. Includes All metals except Metals, nonmetals, Metals. Metals. hydrogen. metalloids, zero group elements. Types o elements Normal elements Normal and inert elements. Transition elements Innertransition elements.

9 9 / MT PAPER () (a) Concave lens and Convex lens : Concave lens Convex lens (i) It is called diverging lens. (i) It is called converging lens. (ii) This lens is thinner in the centre than at its edges. (iii) The principal ocus is virtual. (iv) The ocal length is negative. (v) This lens is used to correct myopia. (ii) This lens is thicker at the centre than at its edges. (iii) The principal ocus is real. (iv) The ocal length is positive. (v) This lens can be used to correct hypermetropia. 5 (b) A A B F F B O F F Image position: On the same side o lens as object. (c) The image is virtual, erect and magnied.