chemistry 10th class chapter 1, Study notes of Chemistry

Download chemistry 10th class chapter 1 and more Study notes Chemistry in PDF only on Docsity! CHAPTER - 1 /HEMICAL REACTIONS AND EQUATION: ‘Chemical Reactions ‘having different propertis involve chemical changes Point Physical Changes ‘Chemical Changes ‘Product | No new product i formed. | New product is formed = Nature | Reversible Irreversible * Properties | Mostly having same properties. | Having entirely different properties © Example [© Water to ce or ice wo water + Tearing of paper ‘© Buming of paper During Chemical Changes Only a rearrangement of atoms take place Reactant transformed in Products ‘new substance produced as a ‘result of chemical reaction  ">" shows the direction of reaction ACTIVITY ‘Buming of Magnesium ribbon — Cleaned by rubbing with sand paper —» To remove the protective layer of Magnesium oxide—® So that it may readily combine with ai-—e (oxygen) —+Hold ribbon with par of tongs (away from eyes)—e Bum it using a spirit lamp—e Ribbon stats burning (with dazzling white flame)—+ Collec the ash in a watch glass “Magnesium oxide Examples of some chemical Reactions in our daily life Formation of eurd Digestion of food Cooking food Respiration Rusting of fron Burning fuels hangein hangin Colour Temperature ang of | Baring of | Zine + 1,50, | QU Hine water (Siverback” cae wax | Zp Sipe > | Sle ie Heat = HAs)? brown) Mg) Chemical Equatior Simplest way— to write word equation — of chemical reaction —e with the help of —* symbols and formula of substances, Example: 1. Carbon Oxygen ———* Carbon Dioxide (Word equation) c+0, +00, (chemical equation) ‘Combination Reaction Decomposition Reaction Displacement Reaction Double Displacement Reaction Redox Reaction 1. Combination Reaction Twocrmorereictits —> combing —t to give —t Single podect Example: & €(s)+0,(2)-+00.(2) ii 21h (e)+0,(¢) 241.00) ACTIVITY “Take small amount of Calum oxide (uick ime) —* Add water —"25=8 > roduc lake lime calcium hydroxide) and heat, Example: {GaO(s) +H,0(I) ->Ca( OH) (ag) + Heat Quick ime Slaked lime Exothermic Reaction Exo( Exit) —=*!_ along with products Examples of Exothermic Reaction (Clg) +20,()-¥C0,(«)+2H,0(8) Methane (Natural Gas) (0 Rain, Reston Food ->Digest -> Carbohydrate —> Glucose» React with oxygen > provide Energy. (Gidley. (49) + 60, (aq) > 6Co, (aq) + 6H,0(1) + Energy (Gi) Decomposition of vegetable matter -> compost, ‘Substance Used in white washing cao Calcium Oxide (quick time) +H,0(I)-+Ca(OH), (aq) Calcium Hydroxide (Lime water or slaked lime) Reason for use Ca(OH), (a9)+Co,(g) > CaCo,(s)+H0 ‘atmospheric (Calciumcarbonates) (Merble) Give shiny finish to walls after 2 oF 3 day). Note ——> Above reaction is also use for checking the presence of CO: LAST TEN YEAR QUESTIONS AND NCERT QUESTIO" Why should a magnesium ribbon be cleaned before burning in ar? ‘The magnesium ribbon which we use a coating of a white layer of magnesium oxide ‘on its surice. Iti formed by the slow reaction of moist air on i. This hinders the ‘buming of magnesium. So, tis layer is removed by rubbing with sandpaper before uring 2 Write the tlanced equation forthe following chemical reactions CO Hydrogen» Chlorine > Hydrogen chloride (Gi) Barium cri + Alumina suihate -» Barium sulphate +Aluminium chloride (Gi) Sodium + Water > Sodium hydroxide * Hydrogen Ans. () Ha(g)+C1,(g)>2HC1(e) (i) 2840, (a9) + AL ($0,) (aq) > 38380, (8)+2ANCL, (ag) (ii) 2Na(s)+2H,0(1) > 2NaOH (aq) +H, (2) 3 Write a balanced chemical equation with symbols forthe following reactions: () Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride (Gi) Sodium hydroxide solution (in water) reats with hydrochloric acid solution (in ‘water to produce sodium chloride solution and water. ‘Ans. (i) BaCl, (ag) + Na,SO, (aq) > BaSO, (s) +2NaCl(aq) (Gi) NaOH (ag) + HCI(aq) —> NaCl (ag) + H.0(1) os Ans. as Ans. a6 en Q2 a3 ‘A solution ofa substance “X" is used for whitewashing. (@ Name the substance "X" and write is formula. ) Write the reaction ofthe substance "X" named in (i) above with water. (@) The substance "X’ used for whitewashing is quick lime (calcium oxide). Its formula is CaO, ‘What is a balanced chemical equation? Why should the chemical equations be balanced? A balanced chemical equation is one which contains an equal number of atoms of ‘each element on both sides of the equation. For example: 2H, +0,92H,0 According to the law of conservation of mass, matter can neither be created nor estroyed in a chemical reaction, During a chemical reaction, the total mass of ‘eactans and products remain the same. Hence, in a chemical reaction, the number of atoms of the various elements on both sides should be equal. Therefore, a chemical ‘equation isto be balanced in accordance with the law of conservation of mat. “Translate the following statements into chemical equations and then balance them. (4) Hydrogen gas combines with nitrogen to form ammonia (b) Hydrogen sulphide gas combines with nitrogen to form ammonia. () Barium chloride reacts with aluminium sulphate to give aluminium chloride and a _recipitate of barium sulphate. (@) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas (a)Na(g)+3H,(s) — —>2NH,() (b) 2H,S(g)+30,(g) | +2H,0(1)+2S0,(z) (©) 3BaCl, + Al,(SO,), >2AICI+ 3880; (€) 2K(s)+2H,0(1) —2KOH(aq) +H,(2) VERY SHORT ANSWER TYPE QUESTION [1 MARKS ‘Which one i a chemical change — rusting of ron or melting of ron? (CBSE, 2011] Rusting of iron. [Name and state the law whichis kept in mind while we balance a chemical equation. [CBSE, 2 1) Law of conservation of mass. ‘Mass can neither be created nor destroyed during a chemical reaction. ‘State one basic difference between a physical change and a chemical change. [CBSE, 2011), In a physical change, no new substance is formed. In a chemical change, new substance is formed ‘What happens when quicktime is added to water? [CBSE, 2010, 2011), Quick lime reacts with water vigorously to produce slaked lime and a large amount of heat el 2 baat is involved absorbed, CaCO,,, Heat Cas) +CO, (2) Photosynthesis 4 Seng cery bred +6110, 1.0.00) 60,(8) 7 fan va Electrolysis decomposition ‘Thermal decomposition «atid out by eating 2FeS0 yy F041) + $04(8)+80,(8) 20490 )y M2040) + 480) 22) Photolysis Decomposition ‘carried out by sunlight Ade) —Saneo2. a) + sen) soa baths recto Used in black and Shite photography. Carried out by electricity 2H,0(1) ===-42H,(¢) +0, (8) t Water Contains 4 2 parts of Hydrogen Land 1 part of oxygen Ratioof Hand Oin water Eset ecrpyss of wae Take plastic mag Daigo es Firttestppes Insert carbon electrodes (erica nails) Connect to volt batery Filan pith water make water Add some. of dil. H;80,.— To} oy good conductor of | sone Cover the plectroes with ile test es (inverted), Sich pte caret Bubbles of gas formed (at both electrodes) + Bubbles displae water in tes tubes Avéve terminal ‘At ve terminal electrode + 2 volume of Hydrogen gas volume of oxygen 2H,0(1)-¥211,(2)+0.(8)  “Ba owen oa ecto et reaction jn which more react clement laces less eacve element from its ompound. + Fees) + CuSO, (ag)—+ FeSO, (aq)+ Cues) fey ESET i Zils) + CuSO, > 2050,(a9)+Cu(s) Silver White Blue colour less fr ipa tion werneed rect sees $0, +2H,S—92H,0+38 HS+1,—92H1+s 4Na+0,—+2Na,0 2PLO+C—+2P+C0, 15 the process, in which metals are eaten up gradually by the action of ar, moisture or ‘chemical (acid) on their surface. Corrosion is caused mainly by oxidation of metals by oxygen of at. ‘Mos common form of comrosion is Rusting of Irom Metal, ‘Rusting of Iron ‘When an iron object is left in damp air fr a considerable time, it gets covered with red — ‘brown flaky substance called RUST, Chemical formula of RUST s FeOyxH1.0 (Hydrated Iron (IHD) oxide) Chemical Equation of Rusting of Iron is 485¢30.4xH,0—92Fe0, 11,0 © Rusting of iron isa redox reactions © Harmful effect of corrosion Corrosion: Weakens iron and steel objects and structures like railways, car bodies, ‘bridges and ship, ete and cuts short thei ite 2. RANCIDITY ‘The condition produced by oxidation of fats and oils in foods marked by unpleasant smell and taste i called Rancid © It spoils the food materi ‘considerable time and makes prepared in fats and oils which have been kept for ‘Characteristics of Rancid food It gives out unpleasant smell 2. Ithas an unpleasant taste, aepre Qa Methods to prevent development of rancdity of food: By adding anti ~ oxidants to food containing fats and ols. By packaging fat and ol containing food in nitrogen £38. can be retarded by keeping food in refigeratr. By storing food in air tight containers What are Anti Oxidants Iisa substance (Chemical which prevents oxidation “Two most common anti oxidants are: BHA. BHT MERY SHORT ANSWER TYPE QUESTIONS {1 MARKS]. Why is photosynthesis considered an endothermic reaction? [CBSE 2011), ‘Ans. Because heat i absorbed inthis process. 2 Whyis hydrogen peroxide kept in coloured bottles? ICBSE, 2010] ‘Ans. Hydrogen peroxide decomposes into H,O and O, in the presence of sunlight and hence to prevent decomposition, they are Kept in coloured bottles. ‘SHORT ANSWER TYPE QUESTION [2 Marks} A copperplate was dipped into a solution of silver nitrate. After sometime, «black layer was observed on the surface of copper plate. State the reason for it and write chemical equation of the reaction involved. ICBSE, 2016), ‘Ans. Black layer was deposited due to coating of silver, because copper being more reactive than silver, displaced silver from silver nitrate solution, 2AgNO, (aq) +Cu + Cu( NO, ), (aq) +2Ag(s) 2 When iron rod is kept dipped in copper sulphate solution for some time; a brown coating is formed on the iron rod. What change will be observed in the colour ofthe Solution? Also write chemical equation for the reaction involved. CBSE, 2015] Blue colour ofthe solution changes to light green. Reddish brown deposit is formed on the ron ail Fe(s) +Cu80, (aq)—> FeSO, (oq) + Cu(s) 3° When Hydrogen gas is passed over heated copper (Il) oxide, copper and steam are Ans. () CuO(s) +H, (g)—"=+Cu(s) + formed, Write the balanced chemical equation with physical states for this reaction. State what kind of chemical reaction is this? ICBSE, 2015) (e) ) Redox reaction. Q4 Write halanced chemical equations forthe following reactions (Silver bromide on exposure to sunlight decomposes into silver and bromine ')_ Sodium metal reacts with water to form sodium hydroxide and hydrogen gas. Ans. (i) 2AgBr(s) 42g (s) + Br, (8) a6 Ans. Qs Ans. (Gi) 2Na(s) +2H,0(1)—+2NaOH (aq) +H,(2) A student prepares aqueous solutions ofthe following sats. ICBSE, 2015] ‘Copper suphate, ferrous sulphate, sodium sulphate, barium chloride Write the colour of each solution thus formed, Copper sulphate ~ Blue Ferrous sulphate -Pale green Sodium slphate— Milky white Barium Chloride - white Mention the colour of FeSO,7H,O crystals. How does this colour change upon ‘heating? Give balanced chemical equation forthe change. ICBSE, 2012] Light green is the colour of erysalline FeSO,7H.O.. Light green changes to reddish ‘brown or brown upon heat ()FeS0,7H,0—*-+FeS0,7H,0 (i) 2FeS0,<*Fe,0, +80, +80, Barium chloride reacts with aluminium sulphate to give aluminium chloride and tram sulphate (State the two types in which the above reaction can be clasiid. (Gi) Translate the above statement nt a chemical equation (@ Double displacement reaction and Precipitation reaction i) 3BACI, + Al, (80,), —92A1CL, + 3B380,(1) hydrogen gas is passed over heated copper (I) oxide, copper and steam are Term, iets bland coemical equson hr hs escton tod ae (i) the substance oxidized and (Gi the substance reduced in the reaction, Balanced equation: () Substance oxidized = H, (Gi) Substance reduced = CuO SHORT ANSWER TYPE QUESTIONS (3 Marks}, (a) Mention the four information's given by an equation [CBSE, 2013] (b) State the law of conservation of mass as applicable in a chemical reaction. (a) (i) Physical state of reactants and products. (Gi) Conditions such a temperature, pressure, heat et. (Gi) Catalyst involved. ‘v) Change in state. (b) Total mass of the elements present in the products ina chemical reaction has to be ‘equal to the total mass of elements present in the reactants or Mass can neither be ‘ereated nor destroyed in a chemical reaction. When a copper wire was left in silver nitrate solution for some time, it was observed ‘that the solution turned blush green. ICBSE, 2016] {) Explain the observation. Qs Ans. os Ans or Which ofthe following statements about the given reaction are correct? 3Fes) + 4Hs0(g) —> FesOu(s) + 4H (g) (i) Iron metal is getting oxidized Gi) Waters getting reduced (Gil) Water is acting as a reducing agent (iv) Waters ating as an oxidising agent (a), and Git) HYG) —_ 4) (0 i) and iv) i)and (iv) (€) Gi) and (ivy Which ofthe following are exothermic processes? () The reaction of water with quick lime (Gi) Dilution ofan acid (Gi) Evaporation of water {Gv) Sublimation of eamphor (crystals) (andi) —— YC and i) —(E)Dandivy——_—(A)Ciip and Gv (a) and Gi) ‘Three beakers labelled as A, B and C each containing 25 mi of water were taken. A ‘small amount of NaOH, anhydrous CuSOM and NaCI were added othe beakers A, B and C respectively. t was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas, in the case of beaker C, the temperature of the solution falls. Which one of the following statements) is(are) correct? {@) In beakers A and B, the exothermic process has occured, (ii) In beakers A and B, the endothermic process has occurred. (ii) In beaker C exothermic process has occurred. (iv) In beaker C endothermic process has occured. (a) (only (yi) only (and div) —_ (A) (ipand (6) (i) and iv) 'A dilute ferrous sulphate solution was gradually added to the beaker containing ‘acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the ‘observation? (a) KMn0 is an oxidising agent, it oxidises FeSOy (b) FeSO, acts as an oxidising agent and oxidises KMnO, {) The colour disappears due to dilution; no reaction is involved (4) KMn0. isan unstable compound and decomposes in the presence of FeSOs to a colourless compound. (a) KMn0, i an oxidising agent, it oxiises FeSOy Which among the following is(are) double displacement reactions)? () Pb + CuCy + PCI: + Cu (Gi) Nas SO, * BaC; —» BaSO, + 2NaCI (iil) C+ 03» COs (iv) CH, +20; —+ CO, +240 (a) and (iv) (by iiyonly (and iy (A) Giipand vy (b) (i) only Q8 Which among the following statements) is (are) true? Exposure of silver chloride to sunlight fora ong duration turns grey due to {he maton of sve by decomposition of sve crie (i) sublimation of silver chloride (i) decomposition of chlorine gas from silver chloride (iv) oxidation of silver chloride (2) @) only ()and Git) ©) andy) iv) only (@) @) only accompanied by the liberation of heat. This process is calle staking of lime. Calcium hhydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime andthe solution formed? (lis an endothermic reaction I isan exothermic reaction (ii) The pH ofthe resulting solution will be more than seven. (iv) The pH of the resulting solution will be less than seven (2) (and (i ()Gi and Git) — ©) @andivy—_—(4) Gi) and iv) ‘Ans. (b)(i) and Q.10 Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following corectly represents the type of the reaction involved? () Displacement reaction (Gi) Precipitation reaction (ii) Combination reaction {Double displacement reaction (2) 6) only ()Gi) only (Civ) only (4) (i) and Gv) ‘Ans. (€) (i) and (iv) Q.11. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and ‘oxygen gases liberated during electrolysis of water is @rt (o)21 wat wiz ‘Ans. (b)2:1 Q.12 Which ofthe following isare) an endothermic processes)? () Dilation of sulphuric acid Gi) Sublimation of dry ice (ii) Condensation of water vapours ‘Gv Evaporation of water (Gand ii) Gponly(@) poly (4) Gi) and Gv) ‘Ans. (€) (i) and (iv) Q.13 In the double displacement reaction between potassium iodide and aqueous aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate isnot available, which ofthe following can be used in place of lead nitrate? (2) Lead sulphate (insoluble) (b) Lead acetate (6) Ammonium nitrate (@)Povassium sulphate ‘Ans. (b) Lead acetate Q.14 Which of the following gases can be used for storage of fresh sample of an ol for a longtime? (2) Carbon dioxide or oxygen (b) Nitrogen or oxygen (6) Carbon dioxide or helium (€) Helium or nitrogen Ans. (Q) Helium or nitrogen QS The following reaction is used for the preparation of oxygen gas in the laboratory 2K C1Os(#) elispa 2KCUs) + 302(0) Which ofthe fllowing statements) is(are) corect about the reaction? (a) tis a dscomposition reaction and endothermic in nature (b)Itisa combination reaction (6) tis a decomposition reaction and accompanied by the cease of heat (@) tis photochemical decomposition reaction and exothermic nature ‘Ans. (a) tis a decomposition reaction and endothermic in nature Q.16 Which one of the following processes involve chemical reactions? (a) Storing of oxygen gas under pressure in a gas cylinder () Liquefaction of air () Keeping petrol ina china dish in the open (4) Heating copper wire in presence of air at high temperature ‘Ans. _(d) Heating copper wire in the presence of ara high temperature Q.17_ In which ofthe following chemical equation, the abbreviations represent the correct states ofthe reactants and products involved at reaction temperature? 21,0) + 0x0 -+ 21,0%@) ati) + O40) -» 2001) 2M) + Oe) -+ 2800) 240) + One) + 214018) Ams. ©) 18 Which o the following are combination actions? 1.2K c103 “5 2KC1+ 30) 2. MgO + H:0 —+ Mg(OH), 9. 4Al + 30) —+ 2AL05 4. In + FeSO, —> ZnSO, + Fe (2) (and i (oy iy and (iv) (@) Gi) amd iv) (4) Gi) and Git) ‘Ans, (4) (i) and (ii) Q.18 Which ofthe following isa displacement reaction?