Which of the following is not a physical change?
Boiling of water to give water vapour
Melting of ice to give water
Dissolution of salt in water
Combustion of Liquefied Petroleum Gas (LPG)
2. The following reaction is an example of:
\(4NH_3(g) + 5O_2(g) \to 4NO(g) + 6H_2O(g)\)
(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction
(i) and (iv)
(ii) and (iii)
(i) and (iii)
(iii) and (iv)
3. Which of the following statements about the given reaction are correct?
\(3Fe(s) + 4H_2O(g) \to Fe_3O_4(s) + 4H_2(g)\)
(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
(i), (ii) and (iii)
(iii) and (iv)
(i), (ii) and (iv)
(ii) and (iv)
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)
(i) and (ii)
(ii) and (iii)
(i) and (iv)
(iii) and (iv)
Three beakers labelled A, B and C each containing 25 mL of water were taken. NaOH, CuSO4 and NaCl were added to A, B and C respectively. Temperature increased in A and B, but decreased in C. Which 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.
(i) only
(ii) only
(i) and (iv)
(ii) and (iii)
A dilute ferrous sulphate solution is added to acidified KMnO4. The purple colour fades and disappears. Which is the correct explanation?
KMnO4 is an oxidising agent; it oxidises FeSO4.
FeSO4 acts as an oxidising agent and oxidises KMnO4.
Colour disappears due to dilution; no reaction.
KMnO4 decomposes in presence of FeSO4 to a colourless compound.
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
(i) and (iv)
(ii) only
(i) and (ii)
(iii) and (iv)
Exposure of AgCl to sunlight turns it grey due to
(i) formation of silver by decomposition of AgCl
(ii) sublimation of silver chloride
(iii) decomposition with release of chlorine gas from AgCl
(iv) oxidation of silver chloride
(i) only
(i) and (iii)
(ii) and (iii)
(iv) only
Slaking of lime: \(CaO + H_2O → Ca(OH)_2 + \text{heat}\). Which is/are true?
(i) Endothermic reaction
(ii) Exothermic reaction
(iii) pH of solution > 7
(iv) pH of solution < 7
(i) and (ii)
(ii) and (iii)
(i) and (iv)
(iii) and (iv)
BaCl2 + (NH4)2SO4 → BaSO4(s) + 2NH4Cl. This reaction is
(i) Displacement (ii) Precipitation (iii) Combination (iv) Double displacement
(i) only
(ii) only
(iv) only
(ii) and (iv)
In electrolysis of water (a decomposition reaction), the mole ratio of hydrogen and oxygen gases liberated is
1 : 1
2 : 1
4 : 1
1 : 2
Which is/are endothermic process(es)?
(i) Dilution of sulphuric acid (ii) Sublimation of dry ice (iii) Condensation of water vapours (iv) Evaporation of water
(i) and (iii)
(ii) only
(iii) only
(ii) and (iv)
For the yellow ppt of PbI2 in a double displacement reaction with KI, if Pb(NO3)2 is unavailable, which can replace it?
Lead sulphate (insoluble)
Lead acetate
Ammonium nitrate
Potassium sulphate
Which gases can be used to store a fresh oil sample for long time?
CO2 or O2
N2 or O2
CO2 or He
He or N2
Preparation of oxygen in lab: \(2KClO_3(s) \xrightarrow[\text{catalyst}]{\text{Heat}} 2KCl(s) + 3O_2(g)\). Which statement(s) is/are correct?
Decomposition reaction and endothermic in nature
Combination reaction
Decomposition reaction accompanied by release of heat
Photochemical decomposition and exothermic
Which process involves a chemical reaction?
Storing O2 at high pressure in a cylinder
Liquefaction of air
Keeping petrol in an open dish
Heating copper wire in air at high temperature
Which equation correctly shows states at reaction temperature?
(a) \(2H_2(l)+O_2(l)→2H_2O(g)\) (b) \(2H_2(g)+O_2(l)→2H_2O(l)\) (c) \(2H_2(g)+O_2(g)→2H_2O(l)\) (d) \(2H_2(g)+O_2(g)→2H_2O(g)\)
(a)
(b)
(c)
(d)
Which of the following are combination reactions?
(i) \(2KClO_3 \xrightarrow{\text{Heat}} 2KCl + 3O_2\)
(ii) \(MgO + H_2O → Mg(OH)_2\)
(iii) \(4Al + 3O_2 → 2Al_2O_3\)
(iv) \(Zn + FeSO_4 → ZnSO_4 + Fe\)
(i) and (iii)
(iii) and (iv)
(ii) and (iv)
(ii) and (iii)
19. 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 \(H_2SO_4\).
(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
20. 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.
21. Complete the missing components/variables given as x and y in the following reactions:
(a) \(Pb(NO_3)_2(aq) + 2KI(aq) \to PbI_2(x) + 2KNO_3(y)\)
(b) \(Cu(s) + 2AgNO_3(aq) \to Cu(NO_3)_2(aq) + x(s)\)
(c) \(Zn(s) + H_2SO_4(aq) \to ZnSO_4(x) + H_2(y)\)
(d) \(CaCO_3(s) \xrightarrow{x} CaO(s) + CO_2(g)\)
22. 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
23. Identify the reducing agent in the following reactions:
(a) \(4NH_3 + 5O_2 \to 4NO + 6H_2O\)
(b) \(H_2O + F_2 \to HF + HOF\)
(c) \(Fe_2O_3 + 3CO \to 2Fe + 3CO_2\)
(d) \(2H_2 + O_2 \to 2H_2O\)
24. Identify the oxidising agent (oxidant) in the following reactions:
(a) \(Pb_3O_4 + 8HCl \rightarrow 3PbCl_2 + Cl_2 + 4H_2O\)
(b) \(2Mg + O_2 \rightarrow 2MgO\)
(c) \(CuSO_4 + Zn \rightarrow Cu + ZnSO_4\)
(d) \(V_2O_5 + 5Ca \rightarrow 2V + 5CaO\)
(e) \(3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2\)
(f) \(CuO + H_2 \rightarrow Cu + H_2O\)
25. Write the balanced chemical equations for the following reactions:
(a) Sodium carbonate with hydrochloric acid (equal molar) gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate with hydrochloric acid gives sodium chloride, water and carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (\(Cu_2I_2\)), liberates iodine gas and also forms potassium sulphate.
26. Potassium chloride solution mixed with silver nitrate solution gives an insoluble white substance. Write the chemical reaction and mention its type.
27. Ferrous sulphate decomposes with evolution of a gas having the odour of burning sulphur. Write the reaction and identify the type.
Why do fireflies glow at night?
29. Grapes on the plant do not ferment, but after plucking they can. Under what conditions do they ferment? Is it a chemical or a physical change?
30. Which among the following are physical or chemical changes?
(a) Evaporation of petrol (b) Burning of LPG (c) Heating an iron rod to red hot (d) Curdling of milk (e) Sublimation of solid ammonium chloride
31. During reactions of some metals with dilute HCl the following were observed. Explain with reasons:
(a) Silver metal does not show any change.
(b) Temperature of mixture rises when aluminium is added.
(c) Sodium metal reaction is highly explosive.
(d) Bubbles are seen when lead is reacted with the acid.
32. A substance X, an oxide of a group 2 element used in cement industry and present in bones, forms a solution turning red litmus blue on treatment with water. Identify X and write the reactions.
33. Write a balanced chemical equation for each reaction and classify them.
(a) Lead acetate solution with dilute HCl → lead chloride and acetic acid.
(b) Sodium metal added to absolute ethanol → sodium ethoxide and hydrogen gas.
(c) Iron(III) oxide heated with carbon monoxide → iron and carbon dioxide.
(d) Hydrogen sulphide reacts with oxygen gas → solid sulphur and liquid water.
Why is silver chloride stored in dark coloured bottles?
35. Balance the following equations and identify the type of reaction.
(a) \(Mg + Cl_2 \rightarrow MgCl_2\)
(b) \(HgO \xrightarrow{Heat} Hg + O_2\)
(c) \(Na + S \xrightarrow{Fuse} Na_2S\)
(d) \(TiCl_4(l) + Mg(s) \rightarrow Ti(s) + MgCl_2(s)\)
(e) \(CaO(s) + SiO_2(s) \rightarrow CaSiO_3(s)\)
(f) \(H_2O_2(l) \xrightarrow{UV} H_2O(l) + O_2(g)\)
36. A magnesium ribbon burns in oxygen to give a white compound X with light. In nitrogen it continues to burn forming Y.
(a) Write the formulae of X and Y.
(b) Write a balanced equation when X is dissolved in water.
Zinc liberates hydrogen with dilute HCl whereas copper does not. Explain.
38. A silver article turns black after a few days in open air and regains shine on rubbing with toothpaste.
(a) Why does it turn black? Name the phenomenon.
(b) Name the black substance formed and give its chemical formula.
39. On heating blue coloured copper(II) nitrate, a black solid, oxygen and a brown gas X are formed.
(a) Write a balanced chemical equation.
(b) Identify the brown gas X.
(c) Name the type of reaction.
(d) What could be the pH range of an aqueous solution of X?
(a) \[\boxed{\;2\,Cu(NO_3)_2\,(s) \;\xrightarrow{\Delta}\; 2\,CuO\,(s) + 4\,NO_2\,(g) + O_2\,(g)\;}\]
(b) X is nitrogen dioxide, \(NO_2\) (brown gas).
(c) Thermal (heat) decomposition; it is also a redox change.
(d) \(NO_2\) dissolves in water forming acids (\(HNO_2\) and \(HNO_3\)), hence the solution is acidic, typically \(\text{pH} \approx 3\text{–}4\) (certainly < 7).
Give characteristic tests for the gases: (a) CO2 (b) SO2 (c) O2 (d) H2.
(a) CO2: Turns freshly prepared lime water milky (\(Ca(OH)_2 + CO_2 \to CaCO_3\downarrow + H_2O\)); in excess, milkiness clears (\(Ca(HCO_3)_2\) forms). Extinguishes a burning splint.
(b) SO2: Pungent smell; decolourises acidified \(KMnO_4\) (purple → colourless) or turns acidified \(K_2Cr_2O_7\) orange → green; turns moist blue litmus red then bleaches.
(c) O2: Rekindles a glowing splint; absorbed by alkaline pyrogallol (solution turns brown).
(d) H2: Burns with a pop sound when a burning/glowing splint is brought near (forms water).
41. What happens when a piece of
(a) zinc is added to copper sulphate solution?
(b) aluminium is added to dilute hydrochloric acid?
(c) silver is added to copper sulphate solution?
Write the balanced chemical equations wherever a reaction occurs.
(a) Zinc being more reactive displaces copper: \(\boxed{Zn + CuSO_4 \to ZnSO_4 + Cu}\). Copper is deposited.
(b) Aluminium reacts with \(HCl\) (after oxide film is disrupted) to give \(AlCl_3\) and \(H_2\): \(\boxed{2Al + 6HCl \to 2AlCl_3 + 3H_2}\). Temperature rises (exothermic).
(c) Silver is less reactive than copper; no displacement occurs. No reaction.
42. What happens when zinc granules are treated with dilute solutions of
(i) \(H_2SO_4\), (ii) \(HCl\), (iii) \(HNO_3\), (iv) \(NaCl\), (v) \(NaOH\)? Write equations wherever applicable.
(i) & (ii) Zinc liberates hydrogen and forms salt: \(Zn + H_2SO_4 \to ZnSO_4 + H_2\); \(Zn + 2HCl \to ZnCl_2 + H_2\).
(iii) With dilute \(HNO_3\), \(H_2\) is not evolved (oxidising acid). Example: \(3Zn + 8HNO_3(dil) \to 3Zn(NO_3)_2 + 2NO + 4H_2O\) (or \(N_2O\) depending on conditions).
(iv) Aqueous \(NaCl\): no reaction (neutral salt) under ordinary conditions.
(v) With \(NaOH\) (zinc is amphoteric): hydrogen is evolved and sodium zincate forms, e.g. \(Zn + 2NaOH + 2H_2O \to Na_2[Zn(OH)_4] + H_2\) (or \(Na_2ZnO_2 + H_2\) in hot concentrated base).
43. A drop of barium chloride solution is added to aqueous sodium sulphite and a white precipitate forms.
(a) Write the balanced equation.
(b) What other name can be given to this reaction?
(c) On adding dilute HCl the precipitate disappears. Why?
(a) \(\boxed{BaCl_2(aq) + Na_2SO_3(aq) \to BaSO_3(s)\downarrow + 2NaCl(aq)}\)
(b) Double displacement / precipitation reaction.
(c) \(BaSO_3\) dissolves reacting with acid to give soluble \(BaCl_2\) and \(SO_2\) gas: \(BaSO_3 + 2HCl \to BaCl_2 + SO_2\uparrow + H_2O\); hence the white ppt disappears.
44. You have two containers made of copper and aluminium and the solutions: dilute \(HCl\), dilute \(HNO_3\), \(ZnCl_2\) and water. In which containers can these solutions be safely kept?