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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Name two salts that are used in black and white photography. Give equations of the reactions that occur when these are exposed to sun light |
| Answer» The two salts are silver chloride (AgCl) and silver bromide (AgBr). | |
| 2. |
Rancidity in the food stuff cooked in oil or ghee is prevented by using `"________".` |
| Answer» anti-oxidants | |
| 3. |
(a) Complete the following equation for the chemical reaction `2FeSO_(4) overset("heat")to Fe_(2)O_(3) + ……………..` (b) What happens when water is added to quick lime ? Write chemical equation. |
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Answer» (a) `2FeSO_(4) overset("heat")to Fe_(2)O_(3) + SO_(2) + SO_(3).` (b) When water is added to quick lime (CaO), slaked lime `Ca(OH)_(2)` is formed `CaO + H_(2)O to Ca(OH)_(2)`? |
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| 4. |
(a) Write the chemical equation in the balanced form. `Fe(s) + H_(2)O(g) to Fe_(3)O_(4)(s) + H_(2)(g)` (b) Identify the type of reaction from the equation given below : `Na_(2)SO_(4)(aq) + BaCl_(2) (aq) to BaSO_(4)(s) + NaCI(aq)` (c) You could have noted that when copper powder is heated in a china dish, the surface of copper powder gets coated with black coloured substance. (i) Why is this black coloured substance formed ? (ii) What is this black substance ? (iii) Write the chemical equation of the reaction taking place. |
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Answer» (a) `3Fe(s) + 4H_(2)O(g) to Fe_(3)O_(4)(s) + 4H_(2)(g)` (b) It is a double displacement reaction also called precipitation reaction. A white precipitate of `BaSO_(4)` is formed in the reaction. (c) (i) The black substance is formed due to the oxidation of copper. (ii) The black substance is cupric oxide or copper (II) oxide with formula CuO. (iii) `2Cu(s) + O_(2)(g) overset("heat")to 2CuO(s)` |
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| 5. |
What happens when : `CO_(2)(g)` is bubbled through lime water (i) in small amount (ii) in excess ? |
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Answer» (i) Solution becomes milky due to the formation of calcium carbonate `Ca(OH)_(2) + CO_(2) to underset("(Milky)")(CaCO_(3)) + H_(2)O` (ii) Milkiness disappeard because calcium carbonate changes to calcium hydrogen carbonate which is colourless in nature. `CaCO_(3) + H_(2)O + CO_(2) to underset("(Colourless)")(Ca(HCO_(3))_(2))` |
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| 6. |
Write the balanced equation for the following chemical reactions. (i) Hydrogen + Chlorine `rarr` Hydrogen chloride (ii) Barium chloride + Aluminium sulphate `rarr` Barium sulphate + Aluminium chloride (iii) Sodium + Water `rarr` Sodium hydroxide + Hydrogen |
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Answer» (i) `H_(2)(g)+Cl_(2)(g)rarr 2HCl(g)` (ii) `3BaCl_(2)(s)+Al_(2)(SO_(4))_(3)(s)rarr 3BaSO_(4)(s)+2AlCl_(3)(s)` (iii) `2Na(s)+2H_(2)O(l) rarr 2NaOH(aq) + H_(2)(g)`. |
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| 7. |
Balance the equation stepwise. Is it posible to produce hydrogen by decomposition of water by means of heat, electricity or light ? |
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Answer» Yes. It is possible to produce hydrogen by decomposition of water. Water decomposes into hydrogen and oxygen gases on passing electric current through acidulated water. This decompoosition takes place by means of electrical energy. `2H_(2)O (l) overset("electric current ") to 2H_(2) uarr +O_(2) uarr` It is called electrolysis. |
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| 8. |
Translate the following statements into chemical equations and then balance them.A. Hydrogen gas combines with nitrogen to form ammonia.B. Hydrogen sulphide gas burns in air to give water and sulpur dioxide.C. Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.D. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. |
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Answer» (a) `3H_(2)(g)+N_(2)(g)rarr 2NH_(3)(g)` (b) `2H_(2)S(g)+3O_(2)(g) rarr 2H_(2)O(l) +2SO_(2)(g)` (iii) `3BaCl_(2)(aq)+Al_(2)(SO_(4))_(3)(aq)(aq) rarr 2AlCl_(3)(aq)+3BaSO_(4)(s)` (d) `2K(s)+2H_(2)O(l) rarr 2KOH(aq)+H_(2)(g)`. |
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| 9. |
Write the balanced chemical equations for the following and identify the type of reaction in each case : (a) `"Barium"+"Potassium"to"Barium"+"Potassium"` `"chloride (aq)"" ""sulphate (aq)"" ""sulphate (s)"" ""chloride (aq)"` (b) `"Zinc carbonate (s)"to "Zinc oxide (s)"+ "Carbon dioxide (g)"` (c ) `"Hydrogen (g)" + "Chlorine (g)"to "Hydrogen chloride (g)"` (d) `"Magnesium (s)"+ underset("acid"(aq))("Hydrochloric")to underset("chloride"(aq))("Magnesium")+ "Hydrogen (g)"` |
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Answer» (a) `2KBr(aq) + BaI_(2)(aq) to 2KI(aq) + BaBr_(2)(aq)` The reaction is known as double displacement reaction. (b) `ZnCO_(3)(s) to ZnO(s) + CO_(2)(g)` The reaction is known as decomposition reaction. (c) `H_(2)(g) + Cl_(2)(g) to 2HCl(g)` The reaction is known as combination reaction (d) `Mg(s) + 2HCl(aq) to MgCl_(2)(aq) + H_(2)(g)` The reaction is known as displacement reaction. |
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| 10. |
Balance the equation stepwise. What is the difference in the process of dissolution and a chemical reaction ? |
| Answer» In dissolution, solute dissolves in the solvent without reacting chemically with it. In chemical reaction, reactants will react chemically with wach other and new products are formed. The bonds in the reactants are broken and new bonds are formed. | |
| 11. |
"We need to balance an unbalanced skeletaal chemical equatio". Justify the statement. |
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Answer» (i) Skeletal chemical equations are either self balanced or unbalanced. (ii) We need to balance the unbalanced chemical equation because off law of conservation of mass which states that "In any reaction, the total mass of each of the elements in the reactants in the same as that of the total mass of each of the respective elements in the products" Therefore, chemical equation must be balanced in each and every chemical reaction. |
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| 12. |
Balance the following chemical equations.A. `HNO_(3) + Ca(OH)_(2) rarr Ca(NO_(3))_(2) + H_(2)O `B. `NaOH + H_(2)SO_(4) rarr N_(2)SO_(4) + H_(2)O`C. `AgCl + AgNO_(3) rarrAgCl +NaNO_(3)`D. `BaCl_(2)+H_(2)SO_(4) rarr BaSO_(4) + BCl` |
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Answer» (i) `2HNO_(3)+Ca(OH)_(2) rarr Ca(NO_(3))_(2)+2H_(2)O` (ii) `2NaOH + H_(2)SO_(4) rarr Na_(2)SO_(4)+2H_(2)O` (iii) `NaCl+AgNO_(3)rarr AgCl + NaNO_(3)` (iv) `BaCl_(2)+H_(2)SO_(4) rarr BaSO_(4)+2HCl`. |
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| 13. |
Which of the statements about the reaction below are incorrect? `2PbO(s) + C(s) rarr 2Pb(s) + CO_(2)(g)` (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced.A. (a) and (b)B. (a) and (c)C. (a), (b) and (c)D. all |
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Answer» Correct Answer - 4 Correct Answer - (a) and (b) |
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| 14. |
A chemical equation shows a chemical reaction using symbols and chemical formulae instead of words. |
| Answer» Correct Answer - True | |
| 15. |
Representation of a chemical reaction in a condensed from using chemical formulae. |
| Answer» Chemical equation | |
| 16. |
When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky. |
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Answer» (i) On heating, limestone undergoes thermal decomposition to form calcium oxide (quick lime) and carbon dioxide. `CaCO_(3(s))overset(Delta)tounderset("quick lime")(CaO_((s)))+CO_(2)uarr` (ii) Calcium oxide when dissolved in water forms Calcium hydroxide (lime water). `CaO_((s))+H_(2)O_((l))to underset("Calcium hydroxide")(Ca(OH)_(2(aq)))` (iii) When carbon dioxide is passed through lime water it turns milky due to formation of white precipitate of Calcium carbonate. `Ca(OH)_(2(aq))+CO_(2(g))to underset("Calcium carbonate")(CaCO_(3(s)))+H_(2) O_((l))` |
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| 17. |
Conversion of quick lime into slaked lime is an example of displacement reaction. |
| Answer» False. It is an example of combination reaction. | |
| 18. |
Why does not a wall immediately acquire a white colour when a coating of slaked lime is applied on it ? |
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Answer» Slaked lime as such is not very white. When applied on the wall, `CO_(2)` gas present in air reacts with calcium hydroxide to form calcium carbonate. It is quite white and therefore, imparts white look to the wall. `Ca(OH)_(2) + CO_(2)(g) to CaCO_(3)(s) + H_(2)O (l)` |
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| 19. |
Iron reacts with water (steam) to form ferric oxide liberating hydrogen gas. |
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Answer» The word equation for the reaction is : `"Iron + Water " to " Ferric oxide + Hydrogen"` The symbol equation for the same reaction is : `Fe + H_(2)O to Fe_(2)O_(3) + H_(2)` |
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| 20. |
Identify the substance oxidised and reduced in the reaction : `CuO(s) + Zn(s) to ZnO(s) + Cu(s)`. |
| Answer» Zinc is oxidised to zinc oxide and copper oxide is reduced to copper. | |
| 21. |
What is an oxidation reaction (i) the substance oxidised and (ii) the substance reduced: ZnO+ C `to` Zn + CO |
| Answer» Oxidation involves the addition of oxygen or the removal of hydrogen in a chemical reaction. In the given reaction, carbon is oxidised to carbon monoxide while zinc oxide is reduced to zinc. | |
| 22. |
The following reaction is an example of a `4NH_(3)(g)+5O_(2)(g)rarr4NO(g)+6H_(2)O(g)` 1. displacement reaction 2.combination reaction3. redox reaction 4.neutralisation reactionA. (i) and (iv)B. (ii) and (iii)C. (i) and (ii)D. (iii) and (iv) |
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Answer» Correct Answer - C Oxygen has displaced hydrogen from `NH_(3)`. It is also a combustion reaction. |
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| 23. |
A process in which some substance undergo bond breaking and are transformed into new substances by formation of new bonds. |
| Answer» Chemical reaction | |
| 24. |
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 |
| Answer» (a) Endothermic (b) Exothermic (c) Exothermic (d) Endothermic. | |
| 25. |
(a) Why is it necessary to balance a chemical equation ? (b) Write the balanced chemical equations for the following reactions : (i) Natural gas burns in air and combines with oxygen to form carbon dioxide and water. (ii) During respiration, glucose combines with oxygen and forms carbon dioxide and water along with the release of energy. |
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Answer» (b) `{:(CH_(4) + 2O_(2) to CO_(2) + 2H_(2)O),("(Natural Gas)"):}` `{:(C_(6)H_(12)O_(6) + 6O_(2) to 6CO_(2) + 6H_(2)O + "energy"),("Glucose"):}` |
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| 26. |
Zinc reacts with dilute sulphuric acid to give zinc sulphate and hydrogen. |
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Answer» The word equation for the reaction is : `"Zinc " + " Sulphuric acid " to " Zinc sulphate " + " Hydrogen "` The symbol equation for the same reaction is : `Zn + H_(2)SO_(4) to ZnSO_(4) + H_(2)` |
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| 27. |
Write a balanced equatin foe the following reaction: Methance burns in oxygen to from carbon dioixide and water. |
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Answer» This reaction can be written in the from of a word equatin as: Methane + Oxygen `to` Carbon dioxide + Water Now, Formula of methance is `CH_(4)` Formula of oxygen is `O_(2)` Formula of carbon dioxide is `CO_(2)` And, Formula of water is `H_(2)O` Writing the formulae of all the substances in he above word equation, we get: `" "CH_(4) + O_(2) to CO_(2) + H_(2)O` Let us count the number of various atoms in reactans and products : `{:(,"In reactants","In products"),("No. of C atoms:",1,1),("No . of H atoms:",4,2),("No .of O atoms",2,3):}` The number of carbon atoms is equal on both the sides (1 each) but the number of hyfdrogen atoms and oxygen atoms is not equal. There are 4 hydrogen atoms on the left side but only 2 hydrogen atoms on the right side, we multiple `H_(2)O` by 2 and write `2H_(2)O.` Thus, `" "CH_(4)+ O_(2)toCO_(2)+2H_(2)O` Counting the number of various atoms on bothj the sides again, we get: `{:(,"In reactants","In products"),("No. of C atoms:",1,1),("No . of H atoms:",4,2),("No .of O atoms",2,3):}` Only the number of oxygen atoms is equal now. There are 2 oxygen atoms on the left side but 4 on the rihgts aise. To have 4 oxygen atoms on the left side, we multiply `O_(2)` by 2 and write `2O_(2):` `" "CH_(4)+2O_(2)toCO_(2)+2H_(2)O` Let us count the number of various atoms on the two sides once agaon: `{:(,"In reactants","In products"),("No. of C atoms:",1,1),("No . of H atoms:",4,4),("No .of O atoms",4,4):}` This chemical equation contains an equal number of various types of atoms in the reactants and products, so this is a balanced equation. |
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| 28. |
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.A. Hydrogen gas and iron chloride are producedB. Chlorine gas and iron hydroxide are producedC. No reaction takes placeD. Iron salt and water are produced. |
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Answer» (a) Ferrous chloride and hydrogen gas are produced according to the reaction `Fe(s) + 2HCl (dil.) to FeCl_(2)(aq) + H_(2)(g)` |
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| 29. |
What happens when a piece of zinc metal is added to copper sulphate solution ? |
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Answer» (i) When a piece of zinc metal is added to copper sulphate solution, more reactive zinc metal displaces the less reactive copper from copper sulphate solution and a solution of zinc sulphate is obtained while copper gets deposited on zinc making it reddish brown in colour. (ii) `Zn_((s))+CuSO_(4(aq))to ZnSO_(4(aq))+Cu_((s))` |
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| 30. |
Convey the following information in the from of a balanced chemical equation : On adding an aqueous solution of sodium hydroxide to an aqueous solution of copper sulphate, copple hydroxide is precipitated and sodium sulphate remains in solution. |
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Answer» In this reaction copper sulphate reacts with sodium hydroxide to from copper hydroxide and sodium sulphate. This can be written in the from of a word equation as : Copper sulphate + sodium hydroxide `to` Copper hydroxide + sodium sulphate `{:(Now",","Formula of copper sulphate is"CuSO_(4)),(,"Formula of sodium hydroxide is"NaO?H),(,"Formula of copper hydroxide is"Cu(OH)_(2)),(And",","Formula of sodium sulphate is Na_(2)SO_(4)):}` Putting these formulae in the above word-equation, we get: `" "CuSO_(4)+NaOHtoCu(OH)_(2)+Na_(2)SO_(4)` Let us count the number of various types of atoms in reactants as well as products. `{:(,"In reactants","In products"),("No . of Cu atoms:",1,1),("No . of S atoms:",1,1),("No . of O atoms:",5,6),("No . of Na atoms:",1,2),("No . of H atoms:",1,2):}` We find that the number of copper atoms and sulphur atoms is equal on both the sides (1 each), but the number of oxygen atoms, sodium atoms and hydrogen atoms is not equal. Let us take the oxygen atoms first. There are 5 oxygen atoms on left side but 6 oxygen atoms on the left side but 6 oxygen atoms on the right side. To have 6 oxygen atoms on the left side, we multiple NaOH by 2 and write 2NaOH. Thus, `" "CuSO_(4)+2NaOHto Cu(OH)_(2)+Na_(2)SO_(4)` Let us count the number of various types of atoms on both the sides once again. `{:(,"In reactants","In products"),("No . of Cu atoms:",1,1),("No . of S atoms:",1,1),("No . of O atoms:",6,6),("No . of Na atoms:",2,2),("No . of H atoms:",1,2):}` This equation contains an equal number of various types of atoms on both the sides, so this is a balanced equation. Copper sulphate is an squeous solution, so we write `CuSO_(4)` (aq) Sodium hydroxide is also an aqueous solution, we write NaOH (aq) Copper hydroxide is formed as a precipitate (solid), so we weite `Cu(OH)_(2)` (s) Sodium sulphate is in solution, so we werite `Na_(2)SO_(4)` (aq) The above equation can now be written as : `CuSO_(4)(aq)+2NaOH(aq)toCu(OH)_(2)(s)+Na_(2)SO_(4)(aq)` |
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| 31. |
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.A. Hydrogen gas and iron chloride are produced.B. Chlorine gas and iron hydroxide are produced.C. No reaction takes place.D. Iron salt and water are produced. |
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Answer» Correct Answer - A Hydrogen gas and iron chloride are produced. |
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| 32. |
You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute `HNO_(3),ZnCl_(2) and H_(2)O`. In which of the containers these solutions can be kept? |
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Answer» Solutions to be kept in copper container : (i) Dilute HCl can be kept since no chemical reaction is expected. Copper is placed below hydrogen in the activity series. (ii) Dilute `HNO_(3)` cannot be kept since a chemical reaction is expected. Nitric acid is a strong oxidising agent. `3Cu (s) + 8HNO_(3) (dil) to 3 Cu(NO_(3))_(2) (aq) + 2NO (g) + 4H_(2)O (aq)` (iii) `ZnCl_(2)` solution can be kept since copper is placed below zinc in the activity series and no chemical reaction is possible. (iv) Water can be kept since no chemical reaction is expected. Solutions to be kept in aluminium container (i) Dilute HCl cannot be kept since aluminium reacts with acid to evolve hydrogen gas. `2Al (s) + 6HCl (aq) to 2AlCl_(3) (aq) + 3H_(2) (g)` (ii) Dilute `HNO_(3)` can be kept . Actually, aluminium is initially oxidised by the acid to aluminium oxide `(Al_(2)O_(3))`. A coating of aluminium oxide gets deposited on the surface of the metal and makes it passive towards reaction with the acid. (iii) `ZnCl_(2)` solution cannot be kept since a chemical reaction will take place as aluminium is placed above zinc in the activity series. `2Al (s) + 3ZnCl_(2) (aq) to 2AlCl_(3) (aq) + 3Zn (s)` (iv) Water as such can be kept in the container. However, we cannot keep steam since a chemical reaction is likely to take place. `2Al (s) + underset("(Steam)")(3H_(2)O (g)) to underset("Aluminium oxide")(Al_(2)O_(3) (s)) + 3H_(2) (g)` |
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| 33. |
Which of the folowing is not an endothermic reactionA. `CaCO_(3)toCaO+CO_(2)`B. `2H_(2)Oto 2H_(2) + O_(2)`C. `6CO_(2)+6H_(2)OtoC_(6)H_(12)O_(6)+6O_(2)`D. `C_(6)H_(12)O_(6)+6O_(2)to6CO_(2)+6H_(2)O` |
| Answer» Correct Answer - D | |
| 34. |
It is recommended to use air tight container for storing oil for long time. |
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Answer» (i) Air, heat and light effect the quality of edible oil, which deteriorates 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 for storing oil for long time, to prevent it from getting oxidised. |
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| 35. |
Write the balanced chemical equations for the following reactions and identify the type of reaction in each case. (a) Iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide. (b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride. (c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine. (d) Ethanol is burnt in air to form carbon dioxide, water and releases heat. |
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Answer» (a) `Fe_(2)O_(3)(s) + 2Al(s) to Al_(2)O_(3)(s) + 2Fe(l) + "Heat" , " " " Displacement reaction/Redox reaction"` (b) `3Mg(s) + N_(2)(g) to Mg_(3)N_(2) (s) , " " " Combination reaction"` (c) `2KI(aq) + Cl_(2)(g) to 2KCl(aq) + I_(2)(s) , " " " Displacement reaction"` (d) `C_(2)H_(5)OH(l) + 3O_(2)(g) to 2CO_(2)(g) + 3H_(2)O(l) + "Heat" , " " " Redox reaction/Combustion reaction"` |
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| 36. |
Write the balanced chemical equations for the following reactions : (i) `"Hydrogen + Chlorine " to " Hydrogen chloride"` (ii) `"Magnesium oxide + Carbon " to " Magnesium + Carbon monoxide"` (iii) `"Phosphorus pentachloride + Water " to " Phosphoric acid + Hydrogen chloride"` (iv) `"Sulphur dioxide + Oxygen " to " Sulphur trioxide"` (v) `"Sodium + Water " to " Sodium hydroxide + Hydrogen"`. |
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Answer» `(i) " "H_(2) + Cl_(2) to 2HCl` `(ii)" "MgO + C to Mg + CO` `(iii)" "PCl_(5) + 4H_(2)O to H_(3)PO_(4) + 5HCl` `(iv)" "2SO_(2) + O_(2) to 2SO_(3)` `(v)" "2Na + 2H_(2)O to 2NaOH + H_(2)` |
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| 37. |
While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphurinc acid is added slowly to water with constant stirring. |
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Answer» (i) Concentrated sulphuring acid `(H_(2)SO_(4))` is a hazardous, highly corrosive chemical. It has a higher density than water and is hygroscopic, which means that it absorbs water from the air. (ii) In the process of dilution of concentrated sulphurinc acid with water, very large amount of heat is liberated. (iii) As result, water gets evaporated instantaneously along with splashing of acid which may cause an accident. (iv) To avoid this, required amount of water is taking in a glass container and small quantity of concentrated sulphuric acid at a time is added with stirring. (v) Therefore, only a small amount of heat is liberated at a time. |
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| 38. |
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas. |
| Answer» Water contains two parts of hydrogen and one part oxygen. Therefore, during the electrolysis of water the amount of hydrogen has collected in one of the test tubes is double than that of the oxygen produced and collected in the other last tube. | |
| 39. |
Write a balanced chemical equation for the process of photosynthesis given the physical states of all substances involved and the conditions of the reaction. |
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Answer» Plants absorb `CO_(2)` present in air and convert the same into glucose and starch in the presence of green colouring matter called chlorophyll present in the plant body and sunlight. The balanced chemical equation for the process is : `{:(6CO_(2)(g) + 6H_(2)O (l) overset("(Chlorophyll)")underset("(Sunlight)")(to) C_(6)H_(12)O_(6)(s) + 6O_(2)(g)),(" ""(Glucose)"):}` |
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| 40. |
During the reaction of some metals with dilute hydrochloric acid, following observations were made. (a) Silver metal does not show any change (b) The temperature of the reaction mixture rises when aluminium (Al) is added `(c)`The reaction of sodium metal is found to be highly explosive (d) Some bubbles of a gas are seen when lead (Pb)is reacted with the acid Explain these observation giving suitable reasons. |
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Answer» (a) Silver (Ag) is placed below hydrogen in the activity series. It cannot replace hydrogen from dilute HCl and no chemical reaction is possible. (b) The reaction of aluminium (Al) with dilute HCl is of exothermic nature. Therefore, the temperature rises. `2Al(s) + 6HCl (aq) to 2AlCl_(3)(aq) + 3H_(2)(g) + "heat"` (c) Hydrogen gas is evolved when sodium metal (Na) is reacted with dilute HCl. The reaction is of exothermic nature. Therefore, hydrogen catches fire accompanied by explosion. `2Na (s) + 2HCl(aq) to 2NaCl(aq) + H_(2)(g) + "heat"` Remember : Sodium metal as such does not catch fire. It is the hydrogen gas evolved which burns since the reaction in highly exothermic in nature. (d) Lead (Pb) reacts with dilute HCl to evolve hydrogen gas accompanied by bubbles. `Pb(s) + 2HCl(aq) to PbCl_(2)(aq) + H_(2)(g).` |
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| 41. |
Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous `CuSO_(4)` and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the followig statement (s) is (are) correct? 1. In beakers A and B, exothermic process has occurred. 2. In beakers A and B, endothermic process has occurred. 3. In beaker C, exothermic process has occurred. 4. In beaker C, endothermic process has occurred.A. (i) onlyB. (ii) onlyC. (i) and (iv)D. (ii) and (iii) |
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Answer» Correct Answer - C Exothermic reactions have occurred in beakers A and B while reaction taking place in beaker C is of endothermic nature. |
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| 42. |
One of the following does not happen during a chemical reacrtion. Thus is:A. Breaking of old chemical bonds and formation of new chemical bondsB. Formation of new substances with entirely different propertiesC. Atoms of one element change into those of another element to from new products.D. A rearrangement of atoms takes place to from new produces. |
| Answer» Correct Answer - D | |
| 43. |
Silver nitrate solution added to solution of sodium chloride. |
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Answer» Silver nitrate reacts with sodium chloride to form a white coloured precipitate of silver chloride and solution of sodium nitrate. `underset("Silver nitrate")(AgNO_(3(aq)))+ underset("Sodium chloride")(NaCl_((aq))) to underset("Silver chloride")(AgCldarr) + underset("Sodium nitrate ")(NaNO_(3(aq)))` |
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| 44. |
Which of the following does not involve a chemical reaction?A. digestion of food in our bodyB. process of respirationC. burning of candle wax when heatedD. melting of candle way on heating |
| Answer» Correct Answer - D | |
| 45. |
(i) What is observed when a solution of potassium iodide to a solution of lead nitrate taken in a test tube ? (ii) What type of reaction is this ? (iii) Write a balanced equation to represent the above reaction. |
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Answer» (i) A yellow precipitate of lead iodide appears at the bottom of the test tube. (ii) It is an example of double displacement reaction. (iii) The balanced equation for the reaction is : `Pb(NO_(3))_(2)(aq) + 2KI(aq) to underset("(Yellow ppt.)")(PbI_(2)(s)) + 2KNO_(3)(aq)` |
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| 46. |
Which of the following is not a physical change?A. Boiling of water to give water vapoursB. Melting of ice to give waterC. Dissolution of salt in waterD. Combustion of Liquefied Petroleum Gas (LPG) |
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Answer» Correct Answer - D LPG is a mixture of gases like propane `(C_(3)H_(8))` and butane `(C_(4)H_(10))` is liquefied form. These are chemical substance and undergo combustion upon heating with air or oxygen. It is therefore, a chemical change. |
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| 47. |
A strip of metal X is dipped in the blue coloured salt solution `YSO_(4)` . After some time, a layer of metal Y from the salt solution is formed on the surface of metal strip X. Metal X is used in galvanisation whereas metal Y is used in making electric wires. Metal X and metal Y togehter form an alloy Z. (a) What could metal X be. (b) What could metal Y be ? (c) Name the metal salt `YSO_(4)`. (d) What type of chemical reaction takes place when metal X reacts with salt solution `YSO_(4)` ? Write the equation of the chemical reaction involved. (e) Name the alloy Z. |
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Answer» (a) Since the metal X is used for galvanisation, it is most probably Zn. (b) Since the metal Y is used in electric cable, it is likely to be cu. (c) The salt is `CuSO_(4).` (d) It is an example of metal displacement reaction. Zn lies above Cu in the activity series and has therefore, displaced Cu from the blue `CuSO_(4)` solution `{:(Zn(s) + CuSO_(4)(aq) to, ZnSO_(4) (aq) + Cu(s)),((X) " "(YSO_(4)), " "(Y)):}` |
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| 48. |
Two metals X and Y from the salts `XSO_(4)` and `Y_(2)SO_(4)` respectively. The solution of salt `XSO_(4)` is blue colour whereas that of `Y_(2)SO_(4)` is colourless. When barium chloride solution is added to `XSO_(4)` solution, then a white precipitate Z is formed along with a salt which turns the solution green. And when barium chloride solution is added to `Y_(2)SO_(4)` solution, then the same white precipitate Z is formed alongwith colourless common salt solution. (a) What could the metals X and Y be ? (b) Write the name and formula of salt `XSO_(4)`. (c) Write the name and formula of salt `Y_(2)SO_(4)`. (d) What is the name and formula of white precipitate Z ? (e) Write the name and formula fo the salt which turns the solution green in the first case. |
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Answer» (a) The available information suggests that metals X and Y are copper (Cu) and sodium (Na) respectively. (b) The salt X is `CuSO_(4)` and its aqueous solution in blue in colour. (c) The salt Y is `Na_(2)SO_(4)` and its aqueous solution is colourless. (d) When `BaCl_(2)` solution is added to `CuSO_(4)` solution, a white precipitate of `BaSO_(4)` (Z) is formed. The solution acquires greenish colour due to formation of `underset((X))(CuSO_(4)) + BaCl_(2) to underset("White ppt (z)")(BaSO_(4)) + underset("Greenish solution")(CuCl_(2))` (e) The green solution as stated above is of cupric chloride. |
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| 49. |
What is meant by the term products of a chemical reactions ? |
| Answer» The substances that the formed after a chemical reaction takes place, are called products of a chemical reaction. | |
| 50. |
The substance in whose presence the rate of a chemical reaction charges without causing any chemical change to it. |
| Answer» Correct Answer - Catalyst | |