chemical reactions and equations

CHEMICAL REACTIONS AND EQUATIONS (Q1.) Identify the component oxidised in the following reaction : H2S + Cl2 S + 2HCl (Ans) H2 S (1 Mark) (Q2.) Define oxidising agent (1 Mark) (Ans) The substance which gives oxygen for oxidation or removes hydrogen is called an oxidising agent (Q3.) Which of the following is a combination and which is a displacement reaction? (a) Cl2 + 2KI → 2KCl + I2 (b) 2K + Cl2 → 2KCl (1 Mark) (Ans) (a) Displacement reaction (b) combination reaction (Q4.) What is catalytic decomposition? (1 Mark) (Ans) Those reactions in which a compound splits up into two or more simpler substances in the presence of catalyst are called catalytic decomposition reactions Example:- Digestion of food in human body (Q5.) What are displacement reactions? (1 Mark) (Ans) The reactions in which more reactive element displaces less reactive element from its salt solution are called displacement reactions 2KI (aq) + Cl2 (g) → 2KCl (aq) + I2 (g) (Q6.) What is meant by oxidation? (1 Mark) (Ans) It is defined as (i) the addition of oxygen or electronegative atom to an element or compound (ii) the removal of hydrogen or electropositive atom from a compound (Q7.) What is a chemical reaction ? (1 Mark) (Ans) In a chemical reaction, old bonds of reactants break and new bonds of products formed (Q8.) Define rancidity (1 Mark) (Ans) The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell, taste and makes food unfit for eating is called rancidity (Q9.) What type of reaction is represented by the digestion of food in our body? (1 Mark) (Ans) Decomposition reaction (Q10.) Why does the colour of copper sulphate solution change when an iron nail is dipped in it? (1 Mark) CONTACT : 096994-12347 Page (Ans) Iron displaces copper from copper sulphate solution and form iron sulphate solution The colour of iron sulphate solution is green (Q11.) What are double displacement reactions? Give an example (1 Mark) (Ans) Double displacement is a reaction in which compounds exchange their ions, i.e two atoms or ions displace each other (Q12.) What are combination reactions? (1 Mark) (Ans) Those reactions in which two or more substances combine to form a single substance, are called combination reactions (Q13.) Define the term reduction (Ans) It is defined as (i) addition of hydrogen or electropositive element to a compound (ii) removal of oxygen or electronegative element from a compound Examples: (i)2Na + H2 → 2NaH (ii) CuO + H2 → Cu + H2O (1 Mark) (Q14.) Define the term corrosion (1 Mark) (Ans) It is defined as the process of slow and gradual conversion of a metal in to their oxides,sulphides,sulphates by the attack of air, water in the atmosphere Example:- Rusting of iron (Q15.) Why we apply paint on iron articles? (Ans) We paint iron articles for protection from rusting (1 Mark) (Q16.) Write the term used for the symbolic representation of a reaction (Ans) Chemical equation (1 Mark) (Q17.) In the following reaction between lead sulphide and hydrogen peroxide: PbS(s) + 4H2O2(aq) → PbSO4(s) + 4H2 (a) Which substance is reduced?`(b) Which substance is oxidised? (1 Mark) (Ans) (a) H2 O2 (b) PbS (Q18.) Identify the substance which is oxidised and which is reduced in the following reaction ZnO +C Zn +CO (1 Mark) (Ans) In this reaction, ZnO is reduced to Zn and C is oxidised to CO (Q19.) Translate the following statements into chemical equations and then balance them a)Sodium chloride with sulphuric acid giving sodium sulphate and hydrochloric acid b)Zinc reacting with silver chloride to give zinc chloride and silver (2 Marks) (Ans) a) 2NaCl + H2 SO4 Na2 SO4 +2 HCl b) 2Zn + AgCl2 2ZnCl2 + Ag (Q20.) Packets of potato chips are filled with a gas Name this gas and explain its use (2 Marks) (Ans) Packets of potato chips are filled with nitrogen gas Oil and fat containing food items are flushed with nitrogen to prevent them from being oxidized They become rancid and their smell and taste change CONTACT : 096994-12347 Page (Q21.) What happens when an iron nail is dipped in copper sulphate solution? (2 Marks) (Ans) When an iron nail is dipped in copper sulphate solution, the blue colour of copper sulphate changes to light green due to the formation of Ferrous sulphate and copper is formed Iron is more reactive than copper, so, iron displaces copper from its salt solution Fe (S) + CuSO4 (aq) FeSO4 (aq) + Cu (S) (Iron) (Blue Solution) (Light Green) (Copper) (Q22.) Write two uses of decomposition reactions (2 Marks) (Ans) 1.These reactions are used to extract several metals from their oxides or other salts When the oxide or salt is electrolysed, metal is obtained For example, aluminium metal is obtained by passing electricity in molten aluminium oxide Digestion of food in our body is also an example of decomposition reaction The starch (carbohydrates) present in food is decomposed to give simple sugar (glucose) and the proteins are broken down into amino acids (Q23.) Why should magnesium ribbon be cleaned before burning in air? (2 Marks) (Ans) Magnesium ribbon should be cleaned before burning in air due to the presence of a thin layer of oxide on the surface of magnesium at ordinary temperature This layer prevents magnesium from further oxidation (Q24.) A solution of a substance ‘X’ is used for white washing (a) Name the substance ‘X’ and write its formula (b) Write the reaction of the substance ‘X’ named in (a) above with water (2 Marks) (Ans) (a) The substance ‘X’ is calcium oxide and its formula is CaO (b) CaO (s)+ H2 O (l) Ca(OH)2 (aq) (Calcium oxide) (Water) (Calcium hydroxide) Or (Slaked Lime) (Q25.) Write a balanced chemical reaction for each of the following reactions: (a) Carbon dioxide is passed through lime water which results in the formation of precipitate of calcium carbonate and water (b) Precipitate of silver metal is formed when a strip of copper metal is dipped in the solution of silver nitrate solution (2 Marks) (Ans) (Q26.) (a)Respiration is considered an exothermic reaction Why? (b) Write an example of exothermic reaction (2 Marks) (Ans) (a) During respiration, food is oxidised and energy is released Therefore, it is considered an exothermic reaction (b) Reaction of quick lime with water is an exothermic reaction 2CaO +2H2 O 2Ca(OH)2 (Q27.) Explain the term combination reaction with the help of an example (2 Marks) (Ans) When two reactants combine to form a single product, the reaction is called combination reaction CONTACT : 096994-12347 Page (Q28.) Write the name of the chemical and its reaction which is used in black and white photography (2 Marks) (Ans) Silver bromide is used in black and white photography It decomposes when exposed to sunlight (Q29.) Give two examples of redox reactions (Ans) (a) ZnO + C Zn + CO (b) MnO2 +4 HCl MnCl2 +2 H2 O + Cl2 (2 Marks) (Q30.) Na2SO4 (aq) +BaCl2(aq) NaCl (s) + BaSO (aq) Is this reaction an example of precipitation reaction? Also give reason for your answer (2 Marks) (Ans) When sodium sulphate is mixed with barium chloride, white cloured barium sulphate is formed which is insoluble in water The insoluble substance is called precipitate and this reacion is called precipitation reaction (Q31.) Write any four observations that help us to determine whether a chemical reaction is taking place (2 Marks) (Ans) (a) Change in state (b) Change in colour (c) Evolution of a gas (d) Change in tempreature (Q32.) Differentiate between combination reaction and decomposition reaction Give one example of each of these reactions (2 Marks) (Ans) Combination reaction Decomposition reaction A reaction in which two or more substances A reaction in which a compound is broken combine to give a single substance is into two or more simpler substances is known as combination reaction known as decomposition reaction A+B AB AB A+B (Q33.) ASO4 + B BSO4 + A (i) Name this reaction (ii) Name the more reactive element (2 Marks) (Ans) (i) It is an example of displacement reaction (ii) Element B is more reactive because it displaces element A from its salt (Q34.) Write one difference between (a) Oxidation and reduction (b) Exothermic and endothermic reactions (2 Marks) (Ans) (a)Addition of oxygen is called oxidation, while addition of hydrogen is called reduction (b) Heat is evolved during exothermic reaction, while heat is absorbed during endothermic reaction (Q35.) In the following reaction, identify the species that undergoes – (i) Oxidation (ii) Reduction Give reasons also Fe(s) + Ni2+ (aq) (Ans) Fe(s) – 2eFe2+(aq) CONTACT : 096994-12347 Fe2+ (aq) + Ni(s) (2 Marks) Page Here, iron loses its two electrons to form Fe2 + ions As we know that oxidation is the loss of electron(s), so iron undergoes oxidation Ni2+ (aq) + 2e- Ni(s) Here, Ni2 + ions gain two electrons to form nickel As we know that reduction is gain of electron(s), so nickel undergoes reduction (Q36.) When sodium sulphate solution is treated with barium chloride solution, a white precipitate is formed Name the reaction and also write the balanced chemical reaction (2 Marks) (Ans) This type of reaction in which two compounds exchange their ions to form two new compounds is called double displacement reaction Na2SO4 (aq) + BaCl2 (aq) BaSO4 (s) + 2NaCl (aq) (Q37.) What you understand by corrosion? (3 Marks) (Ans) The process of slow and gradual conversion of a metal into their compounds by the attack of air and water present in atmosphere is known as corrosion Corrosion, in case of iron is called rusting Rust is hydrated iron III oxide ( Fe2 O3 H2 O) Presence of oxygen and water (moisture) is essential for rusting (Q38.) Write the type of chemical reaction represented by the following equations (i) 2Al(s) + 6HCl(aq) 2AlCl3(aq) + 3H2(g) (ii) 2KBr(aq) + Cl2(g) 2KCl(g) + Br2(g) (iii) 2Zn(s) + O2(g) 2ZnO(S) (3 Marks) (Ans) (i) Redox reaction (ii)Displacement reaction (iii) Combination reaction (Q39.) What is a precipitation reaction? Give example (3 Marks) (Ans) When two compounds in their aqueous state react to form an insoluble residue as one of the products, the residue is known as the precipitate and the reaction is called as precipitation reaction Example- When a solution of silver nitrate is added to a solution of sodium chloride, a white precipitate of silver chloride is obtained and sodium nitrate is formed NaCl + AgNO3 AgCl + NaNO3 Sodium Chloride Silver nitrate Silver Chloride Sodium nitrate (Q40.) What is the difference between combination and decomposition reaction? Give one example of each type (3 Marks) (Ans) Combination reaction – The reaction in which two or more substances (elements or compounds) combine to form a new single product is known as combination reaction For example- 2H2 (g) + O2(g) 2H2 O(l) Decomposition reaction – The reaction in which a single substance decomposes to give two or more substances is known as decomposition reaction.For ex- 2NH3 (g) N2 (g) +3H2(g) Decomposition reactions are opposite to combination reactions (Q41.) (i)What is repiration? (ii)Is resiration exothermic reaction or endothermic? Explain with reason (3 Marks) (Ans) (i)We get energy from food In digestion, food is broken down into simple substances Carbohydrates present in food are broken down to form glucose This glucose combines with Oxygen in the cells of our body and provides energy This reaction is known as respiration C6 H12 O6 + 02 (g) CO2 (g) + 6H2 O (l) + energy Glucose CONTACT : 096994-12347 Page (ii)Since energy is released during the process, respiration is considered as an exothermic reaction (Q42.) Write the balanced equation for the following chemical reactions(a) Sodium + Water Sodium hydroxide + Hydrogen (b) Barium Chloride + Aluminium Sulphate Barium Sulphate + Aluminium Chloride (c) Hydrogen sulphide + Oxygen Water + Sulphur dioxide (3 Marks) (Ans) (a) 2Na + 2H2O 2NaOH + H2 (b) 3BaCl2 + Al2 (SO4)3 BaSO4 + 2AlCl3 (c) 2H2 S +3O2 2H2O +2SO2 (Q43.) What are exothermic and endothermic reactions? Give examples (3 Marks) (Ans) Exothermic reactions: The reactions in which heat is evolved along with the products are known as exothermic reactions For example, (1) Burning of natural gas CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g) + Heat (2) Formation of Ammonia in presence of Ni N2 + 3H2 2NH3 + Heat Nitrogen Hydrogen Ammonia Endothermic reactions The reactions in which heat is absorbed are known as Endothermic reactions.For example, (1) Formation of carbondisulphide C + S + Heat CS2 Carbon Sulphur Carbon disulphide (2) Formation of nitric oxide N2 + O2 + Heat 2NO Nitrogen Oxygen Nitric oxide (Q44.) How a double displacement reaction is different from simple displacement reaction? Explain with the help of an example (3 Marks) (Ans) In a double displacement reaction, exchange of io ns takes place among the reactants, while in displacement reaction more reactive metal displaces less reactive metal from its salt Example of displacement reaction: Fe + CuSO4 Cu + FeSO4 Here, Fe displaces Cu from CuSO4 because Fe is more reactive than Cu Example of double displacement reaction: BaCl2 (aq) + Na2 SO4 (aq) 2NaCl(aq) + BaSO4(s) Here, exchange of ions between reactants takes place (Q45.) Balance the following chemical equations (a) Na + O2 Na2O (b) NaCl + H2O NaOH + Cl2 (c) (NH 4) 2CO3 2NH3 + H2O + + (Ans) (a) 4Na + (b) 2NaCl + (c) (NH 4) 2CO3 H2 CO2 O2 H2O 2Na2O 2NaOH + 2NH3 + Cl2 + H2O + H2 CO2 (3 Marks) (Q46.) Identify the substances that are oxidised and the substances that are reduced in the following reactions (a) Fe + CuSO4 FeSO4 + Cu (b) Fe2O3 +2Al Al2O3 +2Fe (c) MnO2 + 4HCl MnCl2 + 2H2O +Cl2 (3 Marks) CONTACT : 096994-12347 Page (Ans) (a) (b) (c) Fe - Oxidised Fe2 O3 - Reduced MnO2 - Reduced Cu - Reduced Al - Oxidised HCl - Oxidised (Q47.) Explain the terms oxidizing and reducing agents with an example of each (5 Marks) (Ans) Oxidizing agent: The substance, which oxidizes elements or compounds, is known as an oxidizing agent For example: Fe + 3O2 Fe2 O3 Hence, oxygen is an oxidizing agent It oxidizes Iron (Fe3 + ion)to ferric oxide ( Fe2 O3 ) Reducing agent: The substance which reduces an element or a compound is known as reducing agent For example: Stannous chloride is a reducing agent It reduces ferric chloride (Or Fe + ion) to ferrous chloride (or Fe2 +) SnCl2 + 2FeCl3 SnCl4 + 2FeCl2 (Q48.) What is the difference between displacement and double displacement reactions? Write example of each reaction (5 Marks) (Ans) Displacement reaction:The reaction in which one element displaces another element from its compound is known as displacement reaction In these reactions, more reactive element displaces less reactive element from its compound Example2AgNO3 (aq) + Cu(s) Cu (NO3)2 (aq) + 2Ag (s) Silver nitrate Copper Copper nitrate Silver In the above reaction, silver is replaced by copper because copper is more reactive than silver Double displacement reaction: The reaction in which two different atoms or group of atoms (ions) are displaced by other atoms or group of atoms (ions) is known as double displacement reaction Example: Na2 SO4 (aq) + BaCl2 (aq) BaSO4 (s) + 2NaCl(aq) (Sodium Sulphate) (Barium chloride) (Barium Sulphate) (Sodium Chloride) Here, SO42- displaces Cl- ions and Cl- ions displace SO42 - ions or both ions exchange each other These reactions occur in ionic compounds (Q49.) What you understand by a balanced chemical equation? Why should the chemical equation be balanced? (5 Marks) (Ans) A chemical equation which consists of an equal number of atoms of each element on both sides of the equation is known as balanced chemical equation The chemical equation should be balanced due to the following reasons -(a) The number of various types of atoms in reactants must be equal to the number of same type of atoms in products (b) The total mass of all the reactants must be equal to the total mass of the products (c) The number of different types of atoms must be equal on both sides of a chemical equation So, the chemical equation is balanced to satisfy the law of conservation of mass in chemical reaction (Q50.) Write balanced chemical reactions which represent the following: (a) Lead nitrate powder is heated in a test tube (b) Ferrous sulphate is heated (c) Hydrogen gas combines with nitrogen to form ammonia (d) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate CONTACT : 096994-12347 Page (e) Magnesium metal reacts with water to give magnesium hydroxide and hydrogen (5 Marks) (Ans) (Q51.) Balance the following chemical equations (5 Marks) (Ans) (Q52.) Represent the following by balanced chemical equations (a) Iron nail is kept in a copper sulphate solution (b) Silver chloride is kept in sunlight (c) Ferrous sulphate is heated at room temperature (d) Silver nitrate reacts with hydrochloric acid (e) Methane burns in presence of air (5 Marks) (Ans) (Q53.) Write the chemical equation and its type for each of the following: (a) Silver chloride is exposed to sunlight (b) Manganese dioxide reacts with hydrochloric acid (c) Zinc rod is dipped in copper sulphate solution (d) Solution of sodium sulphate and barium chloride are mixed (e) Calcium carbonate is heated (5 Marks) (Ans) (a) It is decomposition reaction CONTACT : 096994-12347 Page (b) It is oxidation reaction (c) It is displacement reaction (d) It is double displacement reaction (e) It is decomposition reaction (Q54.) Write one example of each of the following type of reaction (a) Double displacement reaction (b) Redox reaction (c) Decomposition reaction (d) Combination reaction (e) Displacement reaction (5 Marks) (Ans) (a) Na2 SO4 + BaCl2 BaSO4 + 2NaCl (b) MnO2 + 4HCl MnCl2 + 2H2 O + Cl2 (c) 2Pb(NO3)2 2PbO+ 4NO2 + O2 (d) CaO + H2O Ca(OH)2 (e) Pb +CuCl2 PbCl2 + Cu (Q55.) Name the type of following reaction (a) Na2SO4 + BaCl2 BaSO4 + 2NaCl (b) Pb + CuCl2 PbCl2 + Cu (c) MnO2 + 4HCl MnCl2 + 2H2O + Cl2 (d) CaO + H2O Ca(OH)2 (e) 2Pb(NO3)2 2PbO + 4NO2 + O2 (Ans) (a) Double displacement reaction (b) Displacement reaction (c) Redox reaction (d) Combination reaction (e) Decomposition reaction (5 Marks) (Q56.) When a compound of lead is heated, brown coloured fumes evolve from it (i) Name the compound (ii) Write the balanced chemical equation (iii) Write the chemical name of brown coloured fumes (iv) Name the type of reaction (v) Is this reaction an exothermic or endothermic? (5 Marks) (Ans) (i) The compound is lead nitrate (ii) 2Pb(NO3 )2 2PbO + 4NO2 + O2 (iii) Nitrogen dioxide (iv) Decomposition reaction (v) Endothermic reaction CONTACT : 096994-12347 Page MOST IMPORTANT QUESTIONS (Q1.) Make two separate lists from the given data:-List A comprising of physical changes and List B comprising of chemical changes Conversion of water in ice, burning of paper, breaking of glass bottle, rusting of iron, digestion of food ,falling of leaves from tree, melting of wax candle, Souring of milk (Ans) List A (physical changes):-Conversion of water in ice, breaking of glass bottle, falling of leaves from tree, melting of wax candle List B (chemical changes):-Burning of paper, rusting of iron, digestion of food , curdling of milk (Q2.) Pick and write permanent change/s from following list Powdering of sugar, sublimation of camphor, digestion of food, mixing of sand and salt, ripening of fruits (Ans) Chemical changes are permanent changes Therefore, digestion of food and ripening of fruits are chemical changes (Q3.) Is cutting vegetables into small pieces before cooking is physical or chemical change? Give reason for your answer also (Ans) Yes, cutting vegetables into small pieces before cooking is a physical because no new compound is formed during this process and the vegetables don’t lose their identity (Q4.) Why dissolution of sugar in water is physical change? (Ans) Dissolution of sugar in water is physical change because both sugar and water don’t lose their identity and no new compound is formed (Q5.) My friend says souring of milk is a chemical change Do you agree? Give reasons to support your answer (Ans) Yes, souring of milk is a chemical change because its taste and appearance is different from normal milk (Q6.) In the following reaction identify reactant/s and products X+Y Z (Ans) X and Y are the reactants because they are taking part in a chemical reaction whereas Z is the product because it is the new substance formed during reaction (Q7.) Ammonia is prepared in laboratory according to the following reactionWrite all the information you; get from this reaction (Ans) (i)It tells about the formula, symbols, names & physical status of reactants ( nitrogen and hydrogen) and products (ammonia) ii) It tells one mole nitrogen and three moles hydrogen react to form two moles of ammonia iii) Nitrogen and hydrogen combine in the ratio of 1:3 (Q8.) Write balanced chemical equations for the following chemical reactions (i) Potassium + Water Potassium hydroxide + Hydrogen (ii) Magnesium oxide + Carbon Magnesium + Carbon dioxide (Ans) CONTACT : 096994-12347 Page 10 (Q9.) Balance the following reactions (Ans) (Q10.) Formation of hydrogen chloride is represented as follows Hydrogen + Chlorine Hydrogen chloride Can we call this a chemical equation? Justify your answer (Ans) A chemical equation is representation of chemical change by using symbols and formulas of reactants and products along with the number of atoms and molecules of the reactants are products Since the given representation does not involve symbols and formulae of reactants and products along with the number of atoms and molecules, it is not a chemical equation (Q11.) Name the law which is applicable while balancing chemical equations (Ans) Law of conservation of mass is followed while balancing chemical equations (Q12.) Represent the burning of magnesium by balance chemical reaction (Ans) 2Mg(s) + O2 (g) 2MgO(s) (Q13.) When sulphuric acid is added to zinc granules ,hydrogen gas is evolved along with formation of zinc sulphate Write balance chemical equation for the change (Ans) (Q14.) Translate the following statements into balance chemical equationsHydrogen sulphide is burned in atmosphere of oxygen to form water and sulphur dioxide (Ans) (Q15.) Write a balance chemical reaction for formation of water (Ans) (Q16.) From the following list select combination reactions, displacement reactions, decomposition and double displacement reaction (1) CaCO3 CaO + CO2 (2) NH3 + HCl NH4Cl (3) Zn + H2SO4 ZnSO4 + H2 (4) 2H2 + O2 2H2O (5) AgNO3 + NaCl AgCl + NaNO3 (6) 2HgO 2Hg + O2 (Ans) (1) (2) (3) (4) (5) (6) CaCO3 CaO + CO2 (Decomposition) NH3 + HCl NH4Cl (Combination) Zn + H2 SO4 ZnSO4 + H2 (Displacement) 2H2 + O2 2H2 O (Combination) AgNO3 + NaCl AgCl + NaNO3 (Double displacement) 2HgO 2Hg + O2 (Decomposition reaction) CONTACT : 096994-12347 Page 11 (Q17.) Give an example each of the following types of displacement reactions: (a) metal displaces metal (b) non-metal displaces non-metal (Ans) (a) The reaction in which a metal displaces another metal CuSO4 + Zn ZnSO4 + Cu (b) The reaction in which a non-metal displaces another non-metal 2KBr + Cl2 2KCl + Br2 (Q18.) Identify the substances reduced and the substances oxidized in the following reactions: a ZnO + C Zn + CO b CuO + H2 Cu + H2O c 4Na + O2 (Ans) (i) (ii) (iii) 2Na2O C is oxidized to CO CuO is reduced to Cu Na is oxidized to Na2 O ZnO is reduced to Zn H2 is oxidized to H2O O2 is reduced to O2- (Q19.) A shiny-brown substance X on heating in air turns black and a new compound Y is formed Name the substance X and black compound Y (Ans) X is copper metal Y is copper oxide 2Cu + O2 2CuO (Q20.) Is rusting a physical or chemical change? (Ans) Chemical change (Q21.) Which process is responsible for the rancidity of fatty foods? (Ans) Oxidation (Q22.) When iron nail is dipped in a solution of copper sulphate, a redox reaction takes place: Fe + CuSO4 FeSO4 + Cu (i) Name the substance which is reduced and which is oxidised? (ii) Name the oxidising agent (Ans) (i)Fe is oxidised and CuSO is reduced (ii)CuSO4 is acting as oxidising agent (Q23.) When magnesium burns in chlorine, it forms Magnesium chloride On the basis of electron transfer process, state the following (i) Which element is oxidised? (ii) Which one is reduced? (Ans) Mg + Cl2 MgCl2 Mg + Cl2 Mg2 + + 2Cl– MgCl2 Mg Mg2 + + 2e– (Oxidation) 2Cl + 2e– 2Cl– (Reduction) (i) Mg is oxidized (ii) Cl2 is reduced (Q24.) Oily and fatty food items are flushed with nitrogen gas Why? (Ans)Nitrogen is inert and excludes a direct contact of air with oily and fatty food items CONTACT : 096994-12347 Page 12 (Q25.) Which statement is incorrect for the reaction CuO + H2 Cu + H2O (a) CuO is reduced (b) H2 is oxidised (c) CuO is reduced and H is oxidised (d) Both CuO and H are oxidised (Ans) (d) Both CuO and H2 are oxidised CONTACT : 096994-12347 Page 13