What do you mean by a precipitation reaction?
[question] Question. What do you mean by a precipitation reaction? Explain by giving examples. [/question] [solution] solution: A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction. For example, In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction. Another example of precipitation reaction is In this reaction, barium sulphate is obtained as a precipitate. [/solution]...
In the refining of silver,
[question] Question. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved. [/question] [solution] solution: [/solution]...
What is the difference between displacement and double displacement reactions?
[question] Question. What is the difference between displacement and double displacement reactions? Write equations for these reactions. [/question] [solution] solution: In a displacement reaction, a more reactive element replaces a less reactive element from a compound. $\mathrm{A}+\mathrm{BX} \longrightarrow \mathrm{AX}+\mathrm{B} ;$ where $\mathrm{A}$ is more reactive than B In a double displacement reaction, two atoms or a group of atoms shift places to form new compounds. $\mathrm{AB}+\math...
Write one equation each for decomposition reactions
[question] Question. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity. [/question] [solution] solution: (a) Thermal decomposition (b) Decomposition by light (c) Decomposition by electricity [/solution]...
Why are decomposition reactions called the opposite of combination reactions ?
[question] Question. Why are decomposition reactions called the opposite of combination reactions ? Write equations for these reactions. [/question] [solution] solution: Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy. $\mathrm{AB}+$ Energy $\lo...
Why is respiration considered an exothermic reaction ?
[question] Question. Why is respiration considered an exothermic reaction ? Explain. [/question] [solution] solution: Energy is required to support life. Energy in our body is obtained from the food we eat. During digestion, large molecules of food are broken down into simpler substances such as glucose. Glucose combines with oxygen in the cells and provides energy. The special name of this combustion reaction is respiration. Since energy is released in the whole process, it is an exothermic pro...
What does one mean by exothermic and endothermic reactions?
[question] Question. What does one mean by exothermic and endothermic reactions? Give examples. [/question] [solution] solution: Chemical reactions that release energy in the form of heat, light, or sound are called exothermic reactions. Example: Reaction of sodium and chlorine to yield common salt $\mathrm{Na}(\mathrm{s})+\frac{\mathbf{1}}{\mathbf{2}} \mathrm{Cl}_{2}(\mathrm{~s}) \rightarrow \mathrm{NaCl}(\mathrm{s})+411 \mathrm{~kJ}$ of energy In other words, combination reactions are exotherm...
Write the balanced chemical equation for the following and
[question] Question. Write the balanced chemical equation for the following and identify the type of reaction in each case. (a) Potassium bromide(aq) $+$ Barium iodide(aq) $\rightarrow$ Potassium iodide(aq) $+$ Barium bromide(s) (b) Zinc carbonate(s) $\rightarrow$ Zinc oxide(s) + Carbon dioxide(g) (c) Hydrogen $(\mathrm{g})+$ Chlorine $(\mathrm{g}) \rightarrow$ Hydrogen chloride $(\mathrm{g})$ (d) Magnesium(s) + Hydrochloric acid(aq) $\rightarrow$ Magnesium chloride(aq) $+$ Hydrogen(g) [/questio...
Write the balanced chemical equations for the following reactions.
[question] Question. Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide $+$ Carbon dioxide $\rightarrow$ Calcium carbonate $+$ Water (b) Zinc $+$ Silver nitrate $\rightarrow$ Zinc nitrate $+$ Silver (c) Aluminium $+$ Copper chloride $\rightarrow$ Aluminium chloride $+$ Copper (d) Barium chloride $+$ Potassium sulphate $\rightarrow$ Barium sulphate $+$ Potassium chloride [/question] [solution] solution: (a) $\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{CO}_{2} \right...
Balance the following chemical equations.
[question] Question. Balance the following chemical equations. (a) $\mathrm{HNO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}$ (b) $\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}$ (c) $\mathrm{NaCl}+\mathrm{AgNO}_{3} \rightarrow \mathrm{AgCl}+\mathrm{NaNO}_{3}$ (d) $\mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4}+\mathrm{HCl}$ [/...
Translate the following statements into
[question] Question. Translate the following statements into chemical equations and then balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide. (c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. [/question] [solution] solution: (a) $3 \mathrm{H}_{2}(\mathrm{~g}...
What is a balanced chemical equation ?
[question] Question. What is a balanced chemical equation ? Why should chemical equations be balanced ? [/question] [solution] solution: 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 equation. The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the tot...
What happens when dilute hydrochloric acid is added to iron filings?
[question] Question. What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. [/question] [solution] solution: (a) Hydrogen gas and iron chloride are produced.The reaction is as follows: $\mathrm{Fe}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{FeCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}...
$\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{Fe}$
[question] Question. $\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{Fe}$ The above reaction is an example of a (1) Combination reaction. (2) Double displacement reaction. (3) Decomposition reaction. (4) Displacement reaction. [/question] [solution] solution: (4) The given reaction is an example of a displacement reaction. [/solution]...
Which of the statements about the reaction below are incorrect?
[question] Question. Which of the statements about the reaction below are incorrect? $2 \mathrm{PbO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \rightarrow 2 \mathrm{~Pb}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g})$ (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced. (1) (a) and (b) (2) (a) and (c) (3) (a), (b) and (c) (4) all [/question] [solution] solution: (1) (a) and (b) [/solution]...
Identify the substances that are oxidised and
[question] Question. Identify the substances that are oxidised and the substances that are reduced in the following reactions. (i) $4 \mathrm{Na}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{Na}_{2} \mathrm{O}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g})$ (ii) $\mathrm{CuO}(\mathrm{s})+\mathrm{H}_{2}(\mathrm{~g}) \rightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell)$ [/question] [solution] solution: (i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced....
Give an example of a double displacement reaction other than the one given in Activity 1.10.
[question] Question. Give an example of a double displacement reaction other than the one given in Activity 1.10. [/question] [solution] solution: Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride. In this reaction, sodium carbonate and calcium chloride exchange ions to form two new compounds. Hence, it is a double displacement reaction. [/solution]...
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
[question] Question. Why does the colour of copper sulphate solution change when an iron nail is dipped in it? [/question] [solution] solution: When an iron nail is placed in a copper sulphate solution, iron displaces copper from copper sulphate solution forming iron sulphate, which is green in colour. Therefore, the blue colour of copper sulphate solution fades and green colour appears. [/solution]...
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other?
[question] Question. Why is the amount of gas collected in one of the test tubes in Activity $1.7$ double of the amount collected in the other? Name this gas. [/question] [solution] solution: Water $\left(\mathrm{H}_{2} \mathrm{O}\right)$ contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a ratio of $2: 1$. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas ...
A solution of a substance ' $X$ ' is used for white washing.
[question] Question. A solution of a substance ' $X$ ' is used for white washing. (i) Name the substance ' $X$ ' and write its formula. (ii) Write the reaction of the substance 'X' with water. [/question] [solution] solution: (i) The substance ' $\mathrm{X}$ ' is calcium oxide. Its chemical formula is $\mathrm{CaO}$. (ii) Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime). [/solution]...
Write a balanced chemical equation with state symbols for the following reactions.
[question] Question. Write a balanced chemical equation with state symbols for the following reactions. (i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride. (ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water. [/question] [solution] solution: (i) $\mathrm{BaCl}_{2}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{SO}_{4}$ (aq) $\rightarro...
Write the balanced equation for the following chemical reactions.
[question] Question. Write the balanced equation for the following chemical reactions. (i) Hydrogen + Chlorine Hydrogen chloride (ii) Barium chloride + Aluminium sulphate Barium sulphate + Aluminium chloride (iii) Sodium + Water Sodium hydroxide + Hydrogen [/question] [solution] solution: (i) $\mathrm{H}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{HCl}(\mathrm{g})$ (ii) $3 \mathrm{BaCl}_{2}$ (aq) $+\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(\mathrm{aq}) \righta...