Class 10 Science · 44 questions · 44 with answers
Which of the following is not a physical change?
(d) Combustion of Liquefied Petroleum Gas (LPG)
The following reaction is an example of a 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) (i) displacement reaction (ii) combination reaction (iii) redox reaction (iv) neutralisation reaction
(c) (i) and (iii)
Which of the following statements about the given reaction are correct? 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) (i) Iron metal is getting oxidised (ii) Water is getting reduced (iii) Water is acting as reducing agent (iv) Water is acting as oxidising agent
(c) (i), (ii) and (iv)
Hint: Hint— The substance which oxidises the other substances in a chemical reaction is known as an oxidising agent. Likewise, the substance which reduces the other substance in a chemical reaction is known as reducing agent.
Which of the following are exothermic processes? (i) Reaction of water with quick lime (ii) Dilution of an acid (iii) Evaporation of water (iv) Sublimation of camphor (crystals)
(a) (i) and (ii)
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 following statement(s) is(are) correct? (i) In beakers A and B, exothermic process has occurred. (ii) In beakers A and B, endothermic process has occurred. (iii) In beaker C exothermic process has occurred. (iv) In beaker C endothermic process has occurred.
(c) (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) KMnO4 is an oxidising agent, it oxidises FeSO4
Which among the following is(are) double displacement reaction(s)? (i) Pb + CuCl2 → PbCl2 + Cu (ii) Na2SO4 + BaCl2 → BaSO4 + 2NaCl (iii) C + O2 → CO2 (iv) CH4 + 2O2 → CO2 + 2H2O
(b) (ii) only
Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to (i) the formation of silver by decomposition of silver chloride (ii) sublimation of silver chloride (iii) decomposition of chlorine gas from silver chloride (iv) oxidation of silver chloride
(a) (i) only
Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed? (i) It is an endothermic reaction (ii) It is an exothermic reaction (iii) The pH of the resulting solution will be more than seven (iv) The pH of the resulting solution will be less than seven
(b) (ii) and (iii)
Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved? (i) Displacement reaction (ii) Precipitation reaction (iii) Combination reaction (iv) Double displacement reaction
(d) (ii) and (iv)
Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is
(b) 2:1
Which of the following is(are) an endothermic process(es)? (i) Dilution of sulphuric acid (ii) Sublimation of dry ice (iii) Condensation of water vapours (iv) Evaporation of water
(d) (ii) and (iv)
In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?
(b) Lead acetate
Hint: Hint— Lead sulphate being insoluble will not dissociate into Pb2+ ions.
Which of the following gases can be used for storage of fresh sample of an oil for a long time?
(d) Helium or nitrogen
The following reaction is used for the preparation of oxygen gas in the laboratory Heat 2KClO3 (s) ⎯⎯⎯⎯⎯ Catalyst → 2KCl (s) + 3O2 (g) Which of the following statement(s) is(are) correct about the reaction?
(a) It is a decomposition reaction and endothermic in nature
Which one of the following processes involve chemical reactions?
(d) Heating copper wire in presence of air at high temperature
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
(d) 2H2(g) + O2(g) → 2H2O(g)
Which of the following are combination reactions? Heat → 2KCl + 3O (i) 2KClO3 ⎯⎯⎯⎯ 2 (ii) MgO + H2O ⎯→ Mg(OH)2 (iii) 4Al + 3O2 ⎯→ 2Al2 O3 (iv) Zn + FeSO4 ⎯→ ZnSO4 + Fe
(d) (ii) and (iii) 4 E XEMPLAR P ROBLEMS – SCIENCE 5JQTV#PUYGT3WGUVKQPU
Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.
(b) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
(c) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2SO4 .
(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit reaction, 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.
Complete the missing components/variables given as x and y in the following reactions
(a) Pb(NO3)2 (aq) + 2KI(aq) ⎯→ PbI2 (x) + 2KNO3(y)
(b) Cu(s) + 2Ag NO3(aq) ⎯→ Cu(NO3)2(aq) + x(s)
(c) Zn(s) + H2SO4(aq) ⎯→ ZnSO4(x) + H2(y) x → CaO(s) + CO (g)
(d) CaCO3(s) ⎯⎯⎯ 2
Which among the following changes are exother mic or endothermic in nature?
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(a) Decomposition of ferrous sulphate
(d) Dissolution of ammonium chloride in water
Identify the reducing agent in the following reactions
(a) 4NH3 + 5O2 ⎯→ 4NO + 6H2O
(b) H2O + F2 ⎯→ HF + HOF
(c) Fe2O3 + 3CO ⎯→ 2Fe + 3CO2
(d) 2H2 + O2 ⎯→ 2H2O CHEMICAL REACTIONS AND EQUATIONS 5
Hint: Hint—Reducing agents are those substances which have the ability of adding hydrogen or removing oxygen from the other substances.
Identify the oxidising agent (oxidant) in the following reactions
(a) Pb3O4 + 8HCl ⎯→ 3PbCl2 + Cl2 + 4H2O
(b) 2Mg + O2 ⎯→ 2MgO
(c) CuSO4 + Zn ⎯→ Cu + ZnSO4
(d) V2O5 + 5Ca ⎯→ 2V + 5CaO (e) 3Fe + 4H2O ⎯→ Fe3O4 + 4H2 (f) CuO + H2 ⎯→ Cu + H2O
Write the balanced chemical equations for the following reactions
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2 I2), liberates iodine gas and also forms potassium sulphate.
A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction?
KCl (aq) + AgNO3 (aq) ⎯→ AgCl (s) + KNO3 (aq) It is a double displacement and precipitation reaction. Heat
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.
2FeSO4(s) ⎯⎯⎯ ⎯→ Fe2O3(s) + SO2(g) + SO3(g) It is a thermal decomposition reaction 118 E XEMPLAR P ROBLEMS – SCIENCE
Why do fire flies glow at night?
Fire flies have a protein which in the presence of an enzyme undergoes aerial oxidation. This is a chemical reaction which involves emission of visible light. Therefore, fire flies glow at night.
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?
Grapes when attached to the plants are living and therefore their own immune system prevents fermentation. The microbes can grow in the plucked grapes and under anaerobic conditions these can be fermented. This is a chemical change.
Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(c) Heating of an iron rod to red hot.
(b) Burning of Liquefied Petroleum Gas (LPG)
(d) Curdling of milk (e) Sublimation of solid ammonium chloride
During the reaction of some metals with dilute hydrochloric acid, following observations were made.
Hint— (a) Silver metal does not react with dilute HCl (b) The temperature of the reaction mixture rises when aluminium is added because it is an exothermic reaction. (c) Reaction of sodium metal is found to be highly explosive because it is an exothermic reaction (d) When lead is treated with hydrochloric acid, bubbles of hydrogen gas are evolved Pb + 2HCl → PbCl2 + H2
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.
Calcium oxide CaO(s) + H2O(l) ⎯→ Ca(OH)2(aq)
Write a balanced chemical equation for each of the following reactions and also classify them.
(a) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.
(c) Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
(d) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.
Why do we store silver chloride in dark coloured bottles?
Silver chloride on exposure to sunlight may decompose as per the following rection. 2AgCl ⎯→ 2Ag + Cl2 Therefore, it is stored in dark coloured bottles.
Balance the following chemical equations and identify the type of chemical reaction.
(a) Mg(s) + Cl2(g) ⎯→ MgCl2(s) Heat → Hg(l) + O (g)
(b) HgO(s) ⎯⎯⎯⎯ 2 Fuse → Na S(s)
(c) Na(s) + S(s) ⎯⎯⎯⎯ 2
(d) TiCl4(l) + Mg(s) ⎯→ Ti(s) + MgCl2(s) (e) CaO(s) + SiO2(s) ⎯→ CaSiO3(s) U V → H O(l) + O (g) (f) H2O2(l) ⎯⎯⎯⎯ 2 2
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 burn and forms a compound Y.
(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.
Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why?
Zinc is above hydrogen whereas copper is below hydrogen in the activity series of metals. That is why zinc displaces hydrogen from dilute hydrochloric acid, while copper does not. Zn + HCl ⎯→ ZnCl2 + H2 Cu + HCl ⎯→ No reaction
A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
(b) Name the black substance formed and give its chemical formula. CHEMICAL REACTIONS AND EQUATIONS 7 .QPI#PUYGT3WGUVKQPU
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) Identity the brown gas X evolved.
(c) Identity the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?
Give the characteristic tests for the following gases
(a) CO2
(b) SO2
(c) O2
(d) H2
What happens when a piece of
(a) zinc metal is added to copper sulphate solution?
(b) aluminium metal is added to dilute hydrochloric acid?
(c) silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs
What happens when zinc granules are treated with dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if reaction occurs.
The reaction of Zn granules with (a) Dilute H2SO4 Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) (b) Dilute HCl Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) (c) Dilute HNO3 Reaction with dilute HNO3 is different as compared to other acids because nitric acid is an oxidising agent and it oxidises H2 gas evolved to H2O. 4 Zn(s) + 10HNO3(aq) → 4 Zn(NO3)2 (aq) + 5 H2O(l) + N2O(g) (d) NaCl solution Zn(s) + NaCl (aq) → No reaction (e) NaOH solution Zn(s) + 2 NaOH (aq) → Na2ZnO2 (aq) + H2 (g) Sodium zincate ANSWERS 121
On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.
(a) Write a balanced chemical equation of the reaction involved
(b) What other name can be given to this precipitation reaction?
(c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and H2O. In which of the above containers these solutions can be kept? 8 E XEMPLAR P ROBLEMS – SCIENCE
(A) When solutions are kept in copper container (a) Dilute HCl Copper does not react with dilute HCl. Therefore, it can be kept. (b) Dilute HNO3 Nitric acid acts as a strong oxidising agent and reacts with copper vessel, therefore cannot be kept. (c) ZnCl2 Zinc is more reactive than copper (Cu) therefore, no displacement reaction occurs and hence can be kept. (d) H2O Copper does not react with water. Therefore, can be kept. (B) When solutions are kept in aluminium containers (a) Dilute HCl Aluminium reacts with dilute HCl to form its salt and hydrogen is evolved. Therefore, cannot be kept. 2 Al + 6HCl → 2 AlCl3 + 3 H2 (b) Dilute HNO3 Aluminium gets oxidised by dilute HNO3 to form a layer of Al2O3 and can be kept. (c) ZnCl2 Aluminium being more reactive than zinc can displace zinc ion from the solution. Therefore, the solution cannot be kept. 2 Al + 3 ZnCl2 → 2 AlCl3 + 3Zn (d) H2O Aluminium does not react with cold or hot water. Therefore, water can be kept. Aluminium is attacked by steam to form aluminium oxide and hydrogen 2Al (s) + 3H2O (g) → Al2O3 (s) + 3H2 (g) 122 E XEMPLAR P ROBLEMS – SCIENCE %*#26'4 ANSWERS /WNVKRNG%JQKEG3WGUVKQPU