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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: In a chemical reaction, energy is used for breaking the bonds of the reactants also energy is used in the formation of new bonds. So,... View Article

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) + H2 SO4 (aq) → ZnSO4 (x) + H2 (y) (d) CaCO3 (s) →x CaO(s) + CO2 (g)

Answer: Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as... View Article

Write the balanced chemical equations for the below reaction and identify the type of reaction in the case: Ethanol is burnt in air to form carbon dioxide, water and releases heat.

Answer: Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as... View Article

Write the balanced chemical equations for the below reaction and identify the of reaction in the case: Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid idine.

Answer: Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as... View Article

Write the balanced chemical equations for the below reaction and identify the type of reaction in the case: Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.

Answer: Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as... View Article

Write the balanced chemical equations for the below reaction and identify the type of reaction in the case: Thermite reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.

Answer: Balancing chemical equation refers to balancing the stoichiometric coefficients on the reactants and products side. This must be done as... View Article

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 H2 SO4. (d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.

Answer: (a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas. 3H2 + N2 → 2NH3 The... View Article

Which of the following are combination reactions? (1) 2KClO₃ ⟶(heat) 2KCl + 30₂ (2) MgO + H₂O ⟶ Mg(OH)₂ (3) 4Al + 3O₂⟶ 2Al₂O₃ (4) Zn + FeSO₄ ⟶ ZnSO₄ + Fe (a) (i) and (iii) (b) (iii) and (iv) (c) (ii) and (iv) (d) (ii) and (iii)

Answer: It is defined as a chemical reaction in which two or more substances combine to form a single substance under suitable conditions.... View Article

In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature? (a) 2H₂(I)+O2(I)→2H₂O(g) (b) 2H₂(g)+O₂(0)→2H₂O(I) (c) 2H₂(g)+O₂(g)→2H₂O(I) (d) 2H₂(g)+O₂(g)→2H₂O(g)

Answer: 2H2(g) + O2(g) → 2H2O(l) During the formation of water both hydrogen and oxygen are in gaseous form and produces water in liquid form.... View Article

Which one of the following processes involve chemical reactions? (a) Storing of oxygen gas under pressure in a gas cylinder (b) Liquefaction of air (c) Keeping petrol in a china dish in the open (d) Heating copper wire in presence of air at high temperature

Answer: (d) Heating copper wire in presence of air at high temperature A chemical reaction is in which the bonds are broken within reactant... View Article

The following reaction is used for the preparation of oxygen gas in the laboratory 2KClO3(s)HeatCatalyst2KCl(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 (b) It is a combination reaction (c) It is a decomposition reaction and accompanied by the release of heat (d) It is a photochemical decomposition reaction and exothermic in nature

Answer: (a) It is a decomposition reaction and endothermic in nature 2KClO3 → 2KCl + 3O2 Potassium chlorate decomposes to give potassium... View Article

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? (a) Lead sulphate (insoluble) (b) Lead acetate (c) Ammonium nitrate (d) Potassium sulphate

Answer: (b) Lead acetate The reaction between lead nitrate and potassium iodide is an example of a precipitation reaction. Lead nitrate reacts... View Article

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 (a) (i) only (b) (ii) only (c) (iv) only (d) (ii) and (iv)

Answer: (d) (ii) and (iv) Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. The reaction is an... View Article

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by the 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 (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (iii) and (iv)

Answer: (b) (ii) and (iii) When solid calcium oxide reacts vigorously with water, it forms calcium hydroxide which is accompanied by the... View Article

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 (b) (i) and (iii) (c) (ii) and (iii) (d) (iv) only

Answer: (a) (i) only When silver chloride is exposed to light, it decomposes to form silver metal and chlorine gas. This reaction is used in... View Article

Which among the following is(are) double displacement reaction(s)? (i) Pb + CuCl2 → PbCl2 + Cu (ii) Na2 SO4 + BaCl2 → BaSO4 + 2NaCl (iii) C + O2 → CO2 (iv) CH4 + 2O2 → CO2 + 2H2O (a) (i) and (iv) (b) (ii) only (c) (i) and (ii) (d) (iii) and (iv)

Answer: (b) (ii) only The reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement... View Article

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 (b) FeSO₄ acts as an oxidising agent and oxidises KMnO₄ (c) The colour disappears due to dilution; no reaction is involved (d) KMnO₄ is an unstable compound and decomposes in the presence of FeSO₄ to a colourless compound.

Answer: (a) KMnO4 is an oxidising agent, it oxidises FeSO4 In this reaction, potassium permanganate (KMnO4) is an oxidizing agent. It oxidises... View Article

Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 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 the 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, the exothermic process has occurred. (ii) In beakers A and B, the endothermic process has occurred. (iii) In beaker C exothermic process has occurred. (iv) In beaker C endothermic process has occurred. (a) (i) only (b) (ii) only (c) (i) and (iv) (d) (ii) and (iii)

Answer: (c) (i) and (iv) Exothermic processes will increase the temperature whereas endothermic processes will decrease the temperature. Heat is... View Article

Which of the following statements about the given reaction are correct? 3Fe(s) + 4H₂O(g) → Fe₃O₄ (s) + 4H₂ (g) Iron metal is getting oxidised Water is getting reduced Water is acting as a reducing agent Water is acting as an oxidising agent (a) (i), (ii) and (iii) (b) (iii) and (iv) (c) (i), (ii) and (iv) (d) (ii) and (iv)

Answer: (c) (i), (ii) and (iv) Here, oxygen combines with water to get oxidized. Oxygen is removed from water hence, it is getting reduced. Water... View Article

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 (a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (iii) (d) (iii) and (iv)

Answer: (c) (i) and (iii) The reaction provided is a mixture of displacement and redox reactions. Oxygen displaces hydrogen in the ammonia,... View Article

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