Sunday, April 21, 2019

NCERT text book question answer class 10 chapter 3 metals and non metals

Q1- which of the following pair give displacement reaction ?

(1)NaCi solution and copper metal

(2) MgCi2 solution and silver metal

(3) feso4 solution and copper metal

(4)Agno3 solution and copper metal

Answer---> (4) agno3 solution and copper metal.

Q2-- which if the following method is suitable for preventing an iron frying from rusting ?

(1) applying grease

(2) Applying paint

(3) Applying a coating of zinc

(4) All of the above

ANSWER----> All of the above

Q3--- An element react with oxygen to given compound with a high melting point this compound is also soluble in water the element is likely to be ?

(1)calcium  (3) carbon

(2)silicon (4) iron

ANSWER---->  calcium

Q4---- food are coated with tin and not with zinc because?

(1) zinc is costlier than tin

(2) zinc is more reactive than tin

(3) zinc is less reactive than tin

(4) zinc is a higher melting point than tin

Answer----> zinc is more reactive than tin

Q5----- 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 ?

ANSWER ----> take the given sample of the metal or a non metal beat the sample with hammer and observe if the given material breaks on beating than it is a non metals but if is expands and changes into sheet than it is a metal secondly metals produce sound when they are struck with a hard surface like hammer whereas  non metal produce any sound

(B) taking the help of bulb,wire and switch set up an electric circuit now place the metals to be tested in the circuit between terminals A and B the bulb will glow if they sample is metal the bulb will not glow if they sample is of non metals the glowing of bulb when an iron nail is inserted in between the clips shows the metal goods conductor of electricity

Q6------ what are amphoteric oxides ? Give two examples of amphoteric oxides ?

ANSWER----> those metals oxide which react with both acids as well as bases to produce salts and water are known as amphoteric oxides zinc oxide and aluminium oxide

Q7------- name two metals which will displace hydrogen from dilute acids and two metals qich will not

ANSWER-----> metals which will displace hydrogen from dill acids are magnesium and aluminium metals which are not displace hydrogen from dill acids are copper and gold

Q8-------- in the electrolytic refining if a metal M, what would you take as the anode ,the cathode and the electrolyte

ANSWER-----> (1) ANODE--- crude metal M

(2) cathode -- the strip of pure metal

(3) electrolyte - some salt of metal M

Q9--------- pratyush took sulphur powder on a spatula and heated it he collected the gas evolved by inverting a test tube over it?

(A) what will be the action of gas on

(I) dry litmus paper

(ii) moist litums paper

(B) write the balanced chemical equation for the reaction taking place

Answer ----> [a]

  (I) No change

(II)blue litmus paper turns red
 
[B] SO2(g)+h2o(l)-------> H2so3(aq)----> 2h+(aq)+so3 2-(aq)

Q10---------- state two ways to prevent the rusting of iron ?

ANSWER-----> (1) by applying paint on   the  surface

(2) by coating with zinc

Q11- what type of oxides are formed when non metals combine with oxygen

Answer-----> the oxides formed on reaction of non metals with oxygen are acidic or neutral .
Co2 and So2 are acidic oxides
CO,N2o and h2o are neutral oxides

Give reasons :

(A) platinum ,silver,gold are used to make     
jewellery ?

(B) Sodium potassium and lithium are stored under oil

(C) Aluminum is a highly reactive element yet it is used to make utensils and cooking

(D) carbonate and sulphide ores are usually converted into oxides during the process of extraction

ANSWER -----> (A) these are most ductile malleable and lustrous metals these metals have a little affinity of oxygen and thus are not attacked easily by air or moisture

(B) these react vigorously that they can catch fire even kept in open air hence to protect them they are stored under oil

(C) Aluminium  is a good conductor of electricity more ever when exposed to air its surface gets covered with thin layer of oxides which prevent metal under Neath from further corrosion

(D) it is easier to obtain a metal from its oxide , as compared to its sulphides and carbonates

Q13--- you mist have seen tarnished copper  vessels being cleaned with lemon and tamarind juice explain why this sour substances effective in cleaning the vessels ?

ANSWER --->water does not attack copper but moist atmosphere copper slowly losses its shiny brown surface and forms a green coat this green substance is basic copper carbonate

2cu+co2+h2o+o2----->cucO3.Cu(Oh)2
          -------------------         basic copper
           Moist carbon        carbonate
            Dioxide

The basic carbonate is insoluble in water but it dissolves quickly in the presence of the acids present in acid or tamarined juice .

Q14---- d/b metals and non metals chemical properties

ANSWER----> Metals ->

(1) oxides of metals are either basic in nature or both basic and acidic in nature

(2)metals are electro positive in nature

(3)metals displace hydrogen from dilute acids

(4) metals react with water and produce a metal hydroxide or oxide and hydrogen gas

NON METALS ----> (1)oxides of non metals are either acidic or neutral

(2)non metals are electronegative in nature

(3)  non metal do not replace hydrogen from dilute acid

(4) non metals do not react with water or stem to involve h2 gas as they cannot give electrons to hydrogen ions of water

Q15 -----A Man went door to door passing as a goldsmith he promised to bring back the glitter of old and dull gold ornaments a unspecifying lady give a set of gold bangels to him which he dipped in a particular solution the bangles sparkled like a new but their weight was reduced drastically the lady was upset but after a futile argument the man beat the hasty retreat can you play the detective to find out the nature of the solution he had used  ?

Answer ------> the man used aqua regia which prepared mixture of conc HCI and conc hno3 in the ratio of 3:1 the mixture can dissolve gold but either of these acids cannot dissolve alone aqua regia is highly corrosive,fuming  liquid and is one of the few reagents that can dissolve gold and platinum

Q16 ------ give reason why copper is used to make hot water tanks and not steel ( an alloy of iron )

ANSWER-----> (1) copper do not react with hot water or steam whereas  steel reacts with stem

(2) copper is the one of good conductor of heat as compared to steel

(3) copper has high melting point as compared to steel

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