TextBook Solutions
- A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Element 'X' is copper and the black coloured compound is copper (11) oxide Equation: 2Cu_((s)) + O_(2(g) )→ 2CuO_((s)) 1
- Explain the following in terms of gain or loss of oxygen with two examples each. Oxidation: Addition of oxygen or electronegative element to a atom, molecule, or ion or removal of hydrogen or electropositive element from... 1
- What do you mean by a precipitation reaction? Explain by giving examples. A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.For Example: Na₂CO₃ (aq) + CaCl₂ (a... 1
- In the refining of silver, the recovery of silver from silver nitrate solution involved displacement 2AgNO₃ (aq) + Cu (s) → Cu(NO₃)₂ (aq) + 2Ag (s) Silver Nitrate + Copper → Copper Nitrate + Silver 1
- What is the difference between displacement and double displacement reactions? In a displacement reaction, a more reactive element replaces a less reactive element from a compound. For Example: CuSo₄ (aq) + Zn (s) → ZnS... 1
- Write one equation each for decomposition reactions where energy is supplied Thermal decomposition : read the image for answer https://lh3.googleusercontent.com/-CpMGoV1AuvA/Ya3V5xIPrnI/AAAAAAAAC3I/6WMqQz11TQc2TSOK9X6... 2
- Why are decomposition reactions called the opposite of combination reactions? Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy... 1
- Why is respiration considered an exothermic reaction? Explain. Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of h... 1
- What does one mean by exothermic and endothermic reactions? Give examples. Exothermic reaction:: Reactions in which heat is released along with the formation of products are called exothermic chemical reactions. Eg:... 1
- Write the balanced chemical equation for the following and identify the type of reaction in each case. (a) 2KBr (aq) + BaI₂ (aq) → 2KI (aq) + BaBr₂ (s): Double displacement reaction (b) ZnCO₃ (s) → ZnO (s) + CO₂ (g): Decomposition reaction (c)... 1
- Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide (a) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O (b) Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag (c) 2Al + 3CuCl₂ → 2AlCl₃ + 3Cu (d) BaCl2 + K₂SO₄ → BaSO₄ + 2KCl 1
- Balance the following chemical equations. (i) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O (i) 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O (ii) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O (iii) NaCl + AgNO₃ → AgCl + NaNO₃ (iv) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl 1
- Translate the following statements into chemical equations and then balance them. (a) 3H₂ (g) + N₂ (g) → 2NH₃ (g) (b) 2H₂S (g) + 3O₂ (g) → 2H₂O (l) + 2SO₂ (g) (c) 3BaCl₂ (aq) + Al₂(SO₄)₃ (aq) → 2AlCl₃ (aq) + 3BaSO₄ (s) (d)... 1
- What is a balanced chemical equation? Why should chemical equations be balanced? A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equat... 1
- What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. Correct option is a) Hydrogen gas and iron chloride are produced. 1
- Fe2O3 + 2Al → Al2O3 + 2Fe The above reaction is an example of a Correct option is d) displacement reaction. 2
- Which of the statements about the reaction below are incorrect? 2PbO (s) + C (s) → 2Pb (s) + CO2 (g) Correct option is (i) (a) and (b) 2
- Identify the substances that are oxidised and the substances that are reduced in the following (i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced. (ii) Copper oxide (CuO) is reduced to copper (Cu) while hydrogen (H₂... 1
- Give an example of a double displacement reaction other than the one given in Activity 1.10. Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride. Na₂CO₃+CaCl₂→ CaCO₃+2NaCl In this reaction, sod... 1
- Why does the colour of copper sulphate solution change when an iron nail is dipped in it? When an iron nail dipped in the copper sulphate solution than iron displaces copper from the copper sulphate because iron is more reactive t... 1
- Why is the amount of gas collected in one of the test tubes in Activity 1.7 double Water contains two parts of hydrogen and one part oxygen. Therefore, during the electrolysis of water the amount of hydrogen gas collected i... 1
- A solution of a substance ‘X’ is used for white washing. (i) The substance 'X' is calcium oxide. Its chemical formula is CaO. (ii) Calcium oxide reacts vigorously with water to form calcium hydroxi... 1
- Write the reaction of the substance ‘X’ named in (i) above with water. Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime). CaO (s) + H₂O (l) → Ca(OH)₂ (aq) Calcium Oxide (Quick Li... 2
- (i) Name the substance ‘X’ and write its formula. The substance 'X' is calcium oxide. Its chemical formula is CaO. 1