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question_answer1) Which types of gases can be used for storage of fresh sample of an oil for a long time?
question_answer2) Is burning of a candle wax a physical change or a chemical change?
question_answer3) Write difference between a physical change and a chemical change.
question_answer4) Which one is a chemical change-melting of iron or rusting of iron?
question_answer5) Give one use of quick lime.
question_answer6) Give an example of double displacement reaction. (Write a balanced equation only).
question_answer7) What change in colour is observed when white silver chloride is left exposed in sunlight? State the type of chemical reaction in this change.
question_answer8) Write balanced chemical equation for the following Phosphorus burns in oxygen to give phosphorus pentaoxide
question_answer9) A student took few crystals of sugar in a dry test tube and heated the test tube over flame. The colour of the solution turned black, why?
question_answer10) What precaution should be taken while heating magnesium ribbon over burner?
question_answer11) Using a suitable chemical equation, justify that some chemical reactions are determined by (a) change in colour. (b) change in temperature.
question_answer12) Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.
question_answer13) Which among the following changes are exothermic or endothermic in nature? (a) Decomposition of ferrous sulphate. (b) Dilution of sulphuric acid. (c) Dissolution of sodium hydroxide in water. (d) Dissolution of ammonium chloride in water.
question_answer14) Why do fire flies glow at night?
question_answer15) Why is photosynthesis considered an endothermic reaction?
question_answer16) A substance X, which is an oxide of a group 2 element is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
question_answer17) Why should a magnesium ribbon be cleaned before burning in air ?
question_answer18) On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed. (a) Write a balanced chemical equation of the reaction. (b) Identify the brown gas X evolved. (c) Identify the type of reaction. (d) What could be the pH range of the aqueous solution of the gas X?
question_answer19) Define a combination reaction. Give one example of a combination reaction which is also exothermic.
question_answer20) In the electrolysis of water (a) Name the gas collected at the cathode and anode respectively. (b) Why is the volume of one gas collected at one electrode double that at the other? Name this gas? (c) How will you test the evolved gas?
question_answer21) Seema bought a chips packet and open it. Suddenly her friend Shanu came. She started playing and forgot to eat the chips. On the next day, when she ate the chips, she felt the taste was not good and she was not feeling well. She told to her mother to take her to a doctor. The doctor told them this is because of eating rancid chips. He gave medicines by which Seema became well within a few days. Read the above passage and answer the following questions (a) Why does chips remain fresh for a longer time in a sealed packet? (b) Why did chips of an open packet become rancid? (c) What value do you learn from this passage?
question_answer22) Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a physical or a chemical change?
question_answer23) Identify the type of chemical reaction taking place in each of the following Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed. (b) On heating copper powder in air in a China dish, the surface of copper powder turns black. (c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and small of a gas having odour of burning sulphur is experienced. (d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away. (e) Quick lime reacts vigorously with water releasing a large amount of heat.
question_answer24) Why is combustion of Liquified Petroleum Gas (LPG) a chemical change?
question_answer25) Why should a magnesium ribbon be cleaned before burning in air? [NCERT]
question_answer26) What is wrong with the following equation? Identify the mistake and balance the equation.
question_answer27) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for this reaction.
question_answer28) In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved. [NCERT]
question_answer29) On heating blue coloured powder of copper(II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed. Identify the brown gas X.
question_answer30) Convey the following information in the form of a balanced chemical equation: "An aqueous solution of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form a precipitate of ferrous hydroxide and sodium sulphate remains in solution."
question_answer31) Balance the following chemical equation:
question_answer32) [CBSE Delhi 2009] Give one example of a combination reaction which is also exothermic.
question_answer33) [CBSE Delhi 2009} What happens chemically when quicklime is added to water? [CBSE Delhi 2008]
question_answer34) Why will the colour of heated copper powder become black when air is passed over it?
question_answer35) What is the difference between the following two types of reactions? AgNO3 + HC1 ® AgCl + HNO3 Mg + 2HC1 ® MgCl2 + H2
question_answer36) Why is hydrogen peroxide kept in coloured bottles?
question_answer37) Consider the following reactions: (I) Fe + CuS04 ® FeS04 + Cu {ii) Cu + FeS04 ®CuS04 + Fe Which of these two reactions will take place and why?
question_answer38) Give one example of a reaction which is a double displacement reaction as well as a precipitation reaction.
question_answer39) Why is photosynthesis considered an endothennic reaction?
question_answer40) What type of reaction is represented by the digestion of food in our body?
question_answer41) How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal? [CBSE Delhi 2008]
question_answer42) Can a double displacement reaction take place when the products are highly soluble or highly ionized?
question_answer43) What happens when dilute hydrochloric acid is added to iron filings? Choose the correct answer. Hydrogen gas and iron chloride are produced. Chlorine gas and iron hydroxide are produced. No reaction takes place. Iron salt and water are produced. [NCERT]
question_answer44) What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes? [CBSE Delhi 2010]
question_answer45) Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) ® 2Pb(s) + CO2(g) (a) Lead is getting reduced, (b) Carbon dioxide is getting oxidized. (c) Carbon is getting oxidized, (d) Lead oxide is getting reduced. (i) (a) and (6) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all [NCERT]
question_answer46) Why do we apply paint on iron articles?
question_answer47) In the reaction represented by the following equation: CuO(s) + H2(g) ® Cu(s)+H2O(l) (a)Name the substance oxidized. (b) Name the substance reduced.
question_answer48) Oil and fat containing food items are flushed with nitrogen. Why? [NCERT]
question_answer49) Name the oxidizing and reducing agent in the following reaction: 2H2S + SO2 ® 2H2O + 3S
question_answer50) A dilute ferrous sulphate solution was gradually added to the beaker containing acidified potassium permanganate solution. The light purple colour of the solution fades and finally disappears. Write the correct explanation for this observation.
question_answer51) Define rancidity.
question_answer52) Name one synthetic antioxidant.
question_answer53) What is a balanced chemical equation? Why should the chemical equations be balanced?
question_answer54) How do we come to know that a chemical reaction has taken place?
question_answer55) Why respiration is considered an exothermic reaction? Explain. [NCERT]
question_answer56) Write the balanced chemical equations for the following reactions and identify the type of reaction in each case. (i) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773 K to form ammonia gas. (ii) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water. (iii)Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2SO4. (iv) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light. [NCERT Exemplar]
question_answer57) A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed. [NCERT]
question_answer58) What is an oxidation reaction? Give an example of oxidation reaction. Is oxidation an exothermic or an endothermic reaction? [CBSE Delhi 2009]
question_answer59) Give reasons: (a) Aluminium is a reactive metal but is still used for packing food articles. (b) Red litmus paper turns blue when touched with aqueous solution of magnesium oxide.
question_answer60) Write a balanced chemical equation with state symbols for the following reactions. (i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride. (ii)Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water. [NCERT]
question_answer61) What do you mean by precipitation reactions? Explain with examples. [NCERT]
question_answer62) Translate the following statements into chemical equations and then balance the equations: (i) Phosphorus burns in oxygen to give phosphorus pentoxide. (ii) Aluminium metal replaces iron from ferric oxide, Fe2O, giving aluminium oxide and iron. (iii)Carbon disulphide bums in air to give carbon dioxide and sulphur dioxide. (iv) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
question_answer63) A solution of a substance 'X' is used for whitewashing. (i) Name the substance 'X' and write its formula. (ii) Write the reaction of the substance 'X' named in (i) above with water. [NCERT]
question_answer64) (i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube? (ii) What type of reaction is this? (iii) Write a balanced chemical equation to represent the above reaction. [CBSE (AI) 2009]
question_answer65) What happens when silver chloride is exposed to sunlight? Write a chemical equation for this reaction. Also give one use of such a reaction.
question_answer66) What type of chemical reactions are represented by the following equations? (i) A+B ® C (ii) A+BC ® AC+B (iii) A ® B+C (iv) AS + CD ® AD+BC
question_answer67) Why is the amount of gas collected in one of the test tubes double of the amount collected in the other in electrolysis of water experiment? Name this gas. [NCERT]
question_answer68) Complete the missing components/variables given as x andy in the following reactions: (i) Pb(NO3)2(ag) + 2Kl(aq) ® Pbl2(x) + 2KNO3(y) (ii) Cu(s) + 2AgNO3(ag) ® Cu(NO3)2(aq)+x(s) (iii) Zn(s) + H2SO4(ag) ® ZnSO4(x) + H2(y) (iv) [NCERT Exemplar]
question_answer69) (i) What happens when silver nitrate solution is added to sodium chloride solution? Write the equation for the reaction which takes place. (ii) Name the type of reaction involved.
question_answer70) On adding dilute HCl to copper oxide powder, the solution formed is blue- green. Predict the new compound formed which imparts a blue-green. Colour to the solution. [CBSE Delhi 2008]
question_answer71) Why does the colour of copper sulphate solution change when an iron nail is dipped in it? [NCERT]
question_answer72) Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction. [NCERT Exemplar]
question_answer73) Consider the chemical equation given below and answer the questions that follow: (i) Name the substance which is getting oxidized. (ii)Name the substance which is getting reduced. (iii) Name the oxidizing agent. (iv) Name the reducing agent. (v)What type of a reaction does this equation represent?
question_answer74) Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change? [NCERT Exemplar]
question_answer75) A copper coin was kept dipped in silver nitrate solution for a few hours/days. What will happen to the copper coin? What will happen to the colour of the solution?
question_answer76) (i) What is the colour of ferrous sulphate crystals? How does this colour change after heating? (ii) Name the products formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change? [CBSE Delhi 2009]
question_answer77) Identify the oxidizing agent (oxidant) in the following reactions. (i) (ii) (iii) (iv) (v) (vi)
question_answer78) Solid calcium oxide was taken in a container and water was added slowly to it. (i) State the two observations made in the experiment. (ii) Write the name and chemical formula of the product formed. [CBSE (AI) 2008/C]
question_answer79) A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to bum and forms a compound Y. Write the chemical formulae of X and Y. (ii) Write the balanced chemical equation when X is dissolved in water.
question_answer80) What is the role of a catalyst in a chemical reaction? [CBSE Delhi 2007]
question_answer81) Identify the type of chemical reaction taking place (i) on mixing a solution of potassium chloride with silver nitrate, an insoluble white substance is formed. (ii) on heating green coloured ferrous sulphate crystals, reddish-brown solid is left and smell of a gas having odour of burning sulphur is observed.
question_answer82) Identify the type of reaction in the following examples: (i) Na2SO4(aq) + BaCl2(aq) ® BaSO4(s) + NaCl(aq) (ii) Fe(s) + CuSO4(aq) ® FeS04(aq) + Cu(s) (iii) 2H2(g) + O2(g) ® 2H2O(l) [CBSE Delhi 2008C]
question_answer83) During the reaction of some metals with dilute hydrochloric acid, following observations were made. (i) The temperature of the reaction mixture rises when aluminium (Al) is added. (ii) The reaction of sodium metal is found to be highly explosive. (iii) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid. Explain these observations giving suitable reasons. [NCERT Exemplar]
question_answer84) Give the characteristic tests for the following gases: (i) CO2 (ii) So2 (iii) O2 (iv) H2
question_answer85) Translate the following statements into chemical equations and then balance them. Hydrogen gas combines with nitrogen to form ammonia. Hydrogen sulphide gas bums in air to give water and sulphur dioxide. Barium chloride reacts with aluminium sulphate to give aluminium chemical equations and then balance them chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. (e) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur andliquid water. [NCERT]
question_answer86) What is the difference between displacement and double displacement reactions? Write equations for these reactions.
question_answer87) [NCERT] Write the balanced chemical equations for the following reactions. Calcium hydroxide + Carbon dioxide Calcium carbonate + Water Zinc + Silver nitrate Zinc nitrate + Silver Aluminium + Copper chloride Aluminium chloride + Copper Barium chloride + Potassium sulphate Barium sulphate + Potassium chloride Lead acetate + Dil. Hydrochloric acid Lead chloride + Acetic acid [NCERT]
question_answer88) Write the balanced chemical equation for the following and identify the type of reaction in each case. Potassium bromide(aq) + Barium iodide(aq)Potassium iodide(aq) + Barium bromide(s) Zinc carbonate(s) Zinc oxide(s) + Carbon dioxide(g) Hydrogen(g) + Chlorine(g) ® Hydrogen chloride(g) Magnesium (s) + Hydrochloric acid(aq) Magnesium chloride(aq) + Hydrogen(g) (e) Iron(III) oxide(s) + Carbon monoxide(g) Iron(s) + Carbon dioxide (g) [NCERT]
question_answer89) With the help of an activity explain that hydrogen and oxygen are released when an electric current is passed through water.
question_answer90) What happens when zinc granules are treated with dilute solution of H2SO4, HCl, HNO3, Nad and NaOH? Also write the chemical equations if reaction occurs. [NCERT Exemplar]
question_answer91) (i) Crystals of copper sulphate are heated in a test tube for some time. What is the colour of copper sulphate crystals before heating, and after heating? What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process? (ii) A metal 'X' when dipped in aqueous solution of aluminium sulphate no reaction is observed whereas when it is dipped in an aqueous solution of ferrous sulphate, the pale green solution turns colourless. Identify metal 'X' with reason. [CBSE (AI) 2009]
question_answer92) Samuel had a Silver coin which turned black. He kept the coin in a bowl lined with aluminium foil. Then he filled the bowl with waterand boiled it. After sometime, he found that the coin has become new. Its blackness disappeared. How did it happen?
question_answer93) During electrolysis of water a few drops of sulphuric acid is added into water. Why?
question_answer94) Justify with the help of an example that displacement reaction is also a redox reaction.
question_answer95) Compound 'A' when dissolved in water gives compound 'B' and liberates heat. Compound 'A' is used in whitewashing. Compound 'B' reacts with CO^ to form a white precipitate of compound 'C'. Identify compounds 'A', 'B' and 'C'. Also write the equations involved.
question_answer96) A white salt on heating decomposes to give brown fumes and yellow residue is left behind. Name the salt and write the reaction involved.
question_answer97) When CaO is added to water taken in a beaker, rise in temperature is observed. However, when Ba(OH)2 is mixed with NH4Cl, a fall in temperature is observed. Why?
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