PSEB CLASS 10TH SCIENCE CHAPTER 1 CHEMICAL REACTION AND EQUATION QUESTION ANSWER SOLUTION GUIDE
Chapter 1 of the Class 10th Science textbook by PSEB delves into the intriguing world of chemical reactions and equations. This chapter is an essential part of the curriculum as it introduces students to the basics of chemical reactions and emphasizes the significance of balancing chemical equations.
Chemical reactions form the basis of numerous natural and industrial processes. In this chapter, students are acquainted with the various types of chemical reactions, such as combination reactions, decomposition reactions, displacement reactions, and redox reactions. They also learn about the factors that influence the rate of a chemical reaction, including temperature, concentration, and catalysts.
One of the pivotal topics covered in this chapter is the art of balancing chemical equations. A chemical equation is a symbolic representation of a chemical reaction, showcasing the reactants on the left side and the products on the right side. Balancing the equation is crucial as it ensures that the number of atoms of each element remains the same on both sides of the equation. This is in accordance with the fundamental principle of the conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction, but merely rearranged.
To successfully balance a chemical equation, students are introduced to the concept of stoichiometry. This involves utilizing the coefficients assigned to the reactants and products to determine the ratio of their moles. The chapter provides step-by-step guidance and examples to aid students in grasping the intricacies of balancing chemical equations.
Understanding chemical reactions and equations is of paramount importance for several reasons. It enables us to comprehend how substances interact, how new compounds are formed, and how different reactions find applications in fields such as medicine, industry, and agriculture. Balancing chemical equations holds particular significance as it ensures accurate representation of the reaction, enabling scientists and researchers to study and predict its outcome.
In conclusion, Chapter 1 of the Class 10th Science textbook by PSEB serves as a comprehensive introduction to the captivating realm of chemical reactions and equations. It acquaints students with different types of reactions, explores factors influencing reaction rates, and underscores the significance of balancing chemical equations. This chapter sets the foundation for further exploration in the realm of chemistry, empowering students to develop a profound understanding of the fundamental principles governing chemical reactions.
PSEB CLASS 10TH SCIENCE CHAPTER 1 CHEMICAL REACTION AND EQUATION QUESTION ANSWER SOLUTION GUIDE pdf
here we provide pseb class 10th science chapter 1 full solution in pdf form. you can view and download it in your device
Chapter 1 – ChemiCal ReaCtions and equations
Question 1: Why should a magnesium ribbon be cleaned before burning in air?
Answer– Because there is a layer of magnesium oxide on magnesium ribbon, which does not allow magnesium to react further with oxygen.
Question 2: 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
Answer– (i) H2 + Cl2 -> 2HCl
(ii) 3BaCl2 + Al2 (SO4)3 –> 3BaSO4 + 2AlCl3
(iii) 2Na + 2H2O —> 2NaOH + H2
(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.
Answer- (i) BaCl 2 (aq) + Na2SO4(aq) → BaSO4 (s) + 2NaCl (aq)
(ii) NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
Question 4: 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’ named in (i) above with water.
Answer– (i). The substance ‘X’ is calcium oxide. Its chemical formula is CaO.
(ii) CaO (s) + H2O (l) Ca(OH)2 (aq)
Calcium oxide water Calcium hydroxide
(Quick Lime) (Slaked Lime)
Question 5: 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.
Answer– This activity is of the Electrolysis of water. Water (H2O) contains hydrogen and oxygen in ratio 2:1. Hence quantity of hydrogen gas is double to that of oxygen gas.
Question 6: Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Answer- Due to high reactivity of iron than copper, iron displaces copper from blue copper sulphate solution forming iron sulphate, which is green in colour.
Fe (s) + CuSO4(aq) –> FeSO4(aq) + Cu(s)
Iron+ Copper Sulphate (blue) ->> Iron Sulphate(green) + Copper
Question 7: Give an example of a double displacement reaction other than the one given in Activity 1.10.
Answer- AgNO3 + NaCl –> NaNO3 + AgCl
Silver Nitrate +Sodium Chloride –> Sodium Nitrate + Silver Chloride
Question 8: Identify the substances that are oxidised and the substances that are reduced in the following reactions. (i) 4Na(s) + O2(g) –> 2Na2O(s)
(ii) CuO(s) + H2(g) –> Cu(s) + H2O(l)
Answer- (i) 4Na(s) + O2(g) –> 2Na2O(s) In this reaction Sodium (Na) is oxidized and oxygen (O2) is reduced.
(ii) CuO(s) + H2(g) –> Cu(s) + H20(l) In this reaction Hydrogen (H2) is oxidized and Copper oxide (CuO) is reduced.
EXERCISE
Question 1: Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) –> 2Pb(s) + CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b) ✓ (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all
Question 2: Fe2O3 + 2 Al –> Al2O3 + 2Fe The above reaction is an example of a
(a) Combination reaction.
(b) Double displacement reaction.
(c) Decomposition reaction.
(d) Displacement reaction. ✓
Question 3: What happens when dilute hydrochloric acid is added to iron filings? Tick the correct
(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 4: What is a balanced chemical equation? Why should chemical equations be balanced?
Answer- The chemical equation in which number of atoms of reactants and products are equal. According to law of conservation of mass – “mass can neither be created nor destroyed”. Hence we should balance a chemical equation.
Question 5: Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
Answer- 3H2(g) + N2(g) –> 2NH3(g)
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
Answer- 2H2S(g) + 3O2(g) –> 2H2O + 2SO2
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Answer- 3BaCl2(aq) + Al2(SO4)3 –> 2 AlCl3 + 3BaSO4(s)
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Answer- K(s) + H2O —> KOH + H2
Question 6: Balance the following chemical equations.
(a) HNO3 + Ca(OH)2 –>> Ca(NO3)2 + H2O
Answer – 2HNO3 + Ca(OH)2 –> Ca(NO3)2 + 2H2O
(b) NaOH + H2SO4 Na2SO4 + H2O
(c) NaCl + AgNO3 AgCl + NaNO3
Answer – 2NaOH + H2SO4 —> Na2SO4 + 2H2O
Answer – NaCl + AgNO3 —> AgCl + NaNO3
(d) BaCl2 + H2SO4 —> BaSO4 + HCl
Answer – BaCl2 + H2SO4 —> BaSO4 + 2 HCl
Question 7: Write the balanced chemical equations for the following reactions.n
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
Answer – Ca(OH)2 + CO2 —> CaCO3 + H2O
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
Answer – Zn + 2AgNO3 —> Zn(NO3)2 + 2Ag
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
Answer – 2Al + 3CuCl2 —> 2AlCl3 + 3Cu
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Answer – BaCl2 + K2SO4—> BaSO4 + 2KCl
Question 8: Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide(s)
Answer – 2KBr (aq) + BaI2 (aq) —> 2KI (aq) + BaBr2(s) Type- Double Displacement Reaction
(b) Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)
Answer – ZnCO3 (s) —> ZnO (s) + CO2 Type- Decomposition Reaction.
(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)
Answer – H2 (g) + Cl2 (g) —> 2HCl (g) Type- Combination Reaction
(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)
Answer – Mg (s) + 2HCl (aq) —> MgCl2 (aq) + H2 (g)
Type- Displacement Reaction.
Question 9: What does one mean by exothermic and endothermic reactions? Give examples.
Answer- Exothermic Reactions- Chemical reactions that release energy in the form of heat, light, or sound are called exothermic reactions. Example: Burning of coke, Respiration etc.
Endothermic Reactions- Reactions that absorb energy or require energy in order to proceed are called endothermic reactions. For example: Reaction of coke with steam, photosynthesis reaction etc.
Question 10 : Why is respiration considered an exothermic reaction? Explain.
Answer- Because in respiration oxidation of glucose produce energy, So we can consider this an exothermic reaction. C6H12O6 + 6O2 —>> 6CO2 + 6H2O + Energy
Question 11 : Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer- In combination reactions two or more than two reactants combine to form a single product. But on the other hand in decomposition reactions only a single reactant decompose to form two or more than two products.
Combination Reaction- C + O2 —> CO2
Decomposition Reaction- ZnCO3 —> ZnO + CO2
Question 12 : Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer- (a) Thermal decomposition: CaCO3(s) Heat—> CaO(s) + CO2(g)
(b) Decomposition by light: 2Ag Cl (s) Light —-> 2Ag(s) + Cl2 (g)
(c) Decomposition by electricity: 2H2O (l) Electricity —> 2H2(g) + O2
Question 13 : What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer- In a displacement reaction, a more reactive element replaces a less reactive element from a compound.
For example : Fe (s) + CuSO4(aq) —> FeSO4(aq) + Cu(s)
Iron + Copper Sulphate (blue) —> Iron Sulphate (green)+ Copper.
In a double displacement reaction, two atoms or a group of atoms exchange ions or atoms to form new compounds. For example : AgNO3 + NaCl —> NaNO3 + AgCl
Silver Nitrate+ Sodium Chloride —> Sodium Nitrate + Silver Chloride
Question 14 : In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Answer- 2AgNO3(aq) + Cu (s) —> Cu(NO3)2(aq) + 2Ag (s)
Silver nitrate + copper —> copper nitrate + pure silver
Question 15 : What do you mean by a precipitation reaction? Explain by giving examples.
Answer- A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.
For example: 3BaCl2(aq) + Al2(SO4)3 —> 2 AlCl3 + 3BaSO4(s)
Barium chloride + aluminium sulphate —> aluminium chloride + barium sulphate (precipitate)
Question 16 : Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
Answer- (a) Oxidation is the gain of oxygen or loss of hydrogen.
Examples- (1) C + O2 —> CO2
(2) C6H12O6 + 6O2 —> 6CO2 + 6H2O + Energy
(b) Reduction is the gain of hydrogen or loss of oxygen.
Examples- (1) H2 (g) + Cl2 (g) —> 2HCl (g)
(2) CuO + H2 —> Cu + H2O
Question 17 : A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Answer- ‘X’ is copper (Cu) and the black-coloured compound formed is copper oxide (CuO).
Question 18 : Why do we apply paint on iron articles?
Answer- To prevent iron articles from rusting, we paint them. Paint break the contact of iron with air and moisture.
Question 19 : Oil and fat containing food items are flushed with nitrogen. Why?
Answer- Oil and fat containing food items react with atmospheric oxygen to form poisonous fatty acids, due to which they cause a bad smell. This process is known as rancidity. To prevent food from rancidity, we fill food packets with nitrogen gas which is almost inert gas.
Question 20 : Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
Answer– (a) Corrosion – Surfaces of some metals deteriorate as a result of a chemical reaction with air, moisture, chemicals, etc. This process is known as corrosion of metals. For example, iron, in the presence of moisture, reacts with oxygen to form rust (Fe2O3 xH2O). We can prevent object from corrosion by painting, greasing or galvanization etc.
(b) Rancidity – Oil and fat containing food items react with atmospheric oxygen to form poisonous fatty acids, due to which they cause a bad smell. This process is known as rancidity. To prevent food from rancidity, we fill food packets with nitrogen gas which is almost inert gas.