NCERT Solutions for Class 10 Science Chapter 1-Chemical Reactions and Equations
Best NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations .When materials, referred to as reactants, change into new substances, referred to as products, a chemical reaction takes place. Chemical bonds are broken and reformed during this transition.
Exercise 1
1. Why should a magnesium ribbon be cleaned before burning in air?
Answer: The metal magnesium is reactive. A white layer of magnesium oxide (MgO) will grow on its surface as a result of its reaction with oxygen. Since magnesium oxide is a stable substance, the metal won’t react further. In order to remove the layer of magnesium oxide off the surface of a magnesium ribbon, it is cleaned before being burned in the air.
2. Write the balanced equation for the following chemical reactions.
i) Hydrogen + Chlorine →→ Hydrogen chloride
Answer: The same amount of moles are found on the reactant and product sides of a balanced equation. For the above reaction, the balanced equation is H2(g)+Cl2(g)→2HCl(g).
ii) Barium chloride + Aluminium sulphate →→ Barium sulphate + Aluminium chloride
Answer: The same amount of moles are found on the reactant and product sides of a balanced equation. For the specified reaction, the balanced equation is:3BaSO4(s)+2AlCl3(s) = 3BaCl2(s)+Al2(SO4)3(s).
iii) Sodium + Water →→ Sodium hydroxide + Hydrogen
Answer: The same amount of moles are found on the reactant and product sides of a balanced equation. For the above reaction, the balanced equations are 2Na(s)+2H2O(l)→2NaOH(aq)+H2(g).
3. 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.
Answer: There are an equal number of moles of reactants and products in a balanced chemical equation. The balanced chemical equation is as follows: BaSO4(s)+2NaCl(aq) → BaCl2(aq)+Na2SO4(aq)
ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer: There are an equal number of moles of reactants and products in a balanced chemical equation. The chemical equation in balance is as follows: NaOH(aq)+HCl(aq)→NaCl(aq)+H2O(l)
Exercise 2
1. A solution of a substance ‘X ‘ is used for whitewashing.
i) Name the substance ‘X’ and write its formula.
Answer: Substance “X” is quicklime, or calcium oxide, which is used in whitewashing. CaO is its chemical formula.
ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Answer: The following combination reaction occurs when calcium oxide and water combine to form calcium hydroxide, often known as slaked lime:
s CaO + l H2O → aq Ca(OH)2
2. 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:
Atoms of hydrogen and oxygen make up water. It consists of one oxygen atom and two hydrogen atoms together. Hydrogen travels to the cathode and oxygen to the anode during electrolysis. Thus, the ratio of oxygen to hydrogen is 2:1. Furthermore, hydrogen has twice as much as oxygen.
2H2O→2H2+O2
Exercise 3
1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Answer: Reactive metals displace less reactive metals when an iron nail is immersed in a copper sulphate solution. Consequently, the blue copper sulphate solution fades and turns into a green substance called ferrous sulphate.
2. Give an example of a double displacement reaction other than the one given in Activity 1.10.
Answer: In a double displacement reaction, two ions from the reactants swap places to create new molecules in the products. When potassium iodide and lead nitrate combine to generate lead iodide (a yellow precipitate) and potassium nitrate, this is known as a double displacement reaction.
3. Identify the substances that are oxidised and the substances that are reduced in the following reactions
i) 4Na(s)+O2(g)→2Na2O(s)4Na(s)+O2(g)→2Na2O(s)
Answer:
Any species that gets electrons and lowers its oxidation state is said to be reduced, while any species that loses electrons and raises its oxidation state is said to be oxidised. Oxygen is decreased and sodium (Na) is oxidised.
ii) CuO(s)+H2(g)→Cu(s)+H2O(l)CuO(s)+H2(g)→Cu(s)+H2O(l)
Answer:
Any species that gets electrons and lowers its oxidation state is said to be reduced, while any species that loses electrons and raises its oxidation state is said to be oxidised. As oxygen is lost, copper oxide (CuO) is reduced to copper (Cu), while hydrogen (H2) is oxidised to water (H2O).
CuO+H2−→ΔCu+H2OCuO+H2→ΔCu+H2O
NCERT exercises
1. Which of the statements about the reaction below are incorrect?
2PbO(s)+C(s)→2Pb(s)+CO2(g)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.
Options
i) (a) and (b)
ii) (a) and (c)
iii) (a),(b) and (c)
iv) all
Answer:
Incorrect option is (i) (a) and (b)
Explanation:
(a) The removal of oxygen
(b) The elemental carbon absorbs the oxygen that was taken out of lead.
2. Fe2O3+2Al→Al2O3+2FeFe2O3+2Al→Al2O3+2Fe
The above reaction is an example of a _______________
Options:
a) Combination reaction.
b) Double displacement reaction.
c) Decomposition reaction.
d) Displacement reaction.
Answer:
(d) The given reaction is an example of a single displacement reaction.
Explanation:
Aluminium oxide is created when oxygen from ferrous oxide is transferred to aluminium metal. Because aluminium is more reactive than iron, iron is removed from its oxide in this reaction. A more reactive element replaces a less reactive one in this process, which is called a displacement reaction.
3. 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.
Answer:
(a) Hydrogen gas and iron chloride are produced. The reaction is as follows:
4. What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
The same amount of moles of each element in the reactants and products make up a balanced chemical equation.
The law of conservation of mass states that mass cannot be generated or destroyed, so chemical equations must be balanced. As a result, in a chemical reaction, the mass of all reactants and products should be identical. Because of this, the total mass of the reactants and products in a balanced chemical equation are equal.
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)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(l)+2SO2(g)2H2S(g)+3O2(g)→2H2O(l)+2SO2(g)
c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Answer: 3BaCl2(aq)+Al2(SO4)3(aq)→2AlCl3(aq)+3BaSO4(s)3BaCl2(aq)+Al2(SO4)3(aq)→2AlCl3(aq)+3BaSO4(s)
d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas
Answer: 2K(s)+2H2O(l)→2KOH(aq)+H2(g)2K(s)+2H2O(l)→2KOH(aq)+H2(g)
6. Balance the following chemical equations
a)HNO3+Ca(OH)2→Ca(NO3)2+H2OHNO3+Ca(OH)2→Ca(NO3)2+H2O
Answer:
2HNO3+Ca(OH)2→Ca(NO3)2+2H2O2HNO3+Ca(OH)2→Ca(NO3)2+2H2O
b)NaOH+H2SO4→Na2SO4+H2ONaOH+H2SO4→Na2SO4+H2O
Answer:
2NaOH+H2SO4→Na2SO4+2H2O2NaOH+H2SO4→Na2SO4+2H2O
c)NaCl+AgNO3→AgCl+NaNO3NaCl+AgNO3→AgCl+NaNO3
Answer:
d)BaCl2+H2SO4→BaSO4+HClBaCl2+H2SO4→BaSO4+HCl
Answer:
BaCl2+H2SO4→BaSO4+2HClBaCl2+H2SO4→BaSO4+2HCl
7. Write the balanced chemical equations for the following reactions.
a) Calcium hydroxide + Carbon dioxide →→ Calcium carbonate + Water
Answer: $Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}+{{H}_{2}}O$
b) Zinc + Silver nitrate →→Zinc nitrate +Silver
Answer: Zn+2AgNO3→Zn(NO3)2+2AgZn+2AgNO3→Zn(NO3)2+2Ag
c) Aluminium + Copper chloride →→Aluminium chloride + Copper
Answer: 2Al+3CuCl2→2AlCl3+3Cu2Al+3CuCl2→2AlCl3+3Cu
d) Barium chloride + Potassium sulphate→→Barium sulphate + Potassium chloride
Answer: BaCl2+K2SO4→BaSO4+2KClBaCl2+K2SO4→BaSO4+2KCl
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(aq)2KBr(aq)+BaI2(aq)→2KI(aq)+BaBr2(aq) ; Double displacement reaction
b) Zinc carbonate (s) →→Zinc oxide (s) + Carbon dioxide (g)
Answer:
ZnCO3(s)→ZnO(s)+CO2(g)ZnCO3(s)→ZnO(s)+CO2(g) ; Decomposition reaction
c) Hydrogen (g)+ Chlorine (g)→→Hydrogen chloride (g)
Answer:
H2(g)+Cl2(g)→2HCl(g)H2(g)+Cl2(g)→2HCl(g) ; Combination reaction
d) Magnesium (s) + Hydrochloric acid (aq) →→Magnesium chloride (aq) + Hydrogen (g)
Answer:
Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) ; Single displacement reaction
9. What does one mean by exothermic and endothermic reactions? Give examples.
Answer:
Exothermic Reaction: Exothermic reactions are those in which new products are formed while heat is also evolved. Energy is released to finish these reactions because the reactant energy is greater than the product energy.
Reactant energy exceeds product energy.
Example: Complete combustion of methane gas produces carbon dioxide and water along with heat and light.
Another example of exothermic reactions is respiration and decomposition of vegetable matter.
Endothermic Reaction: Endothermic reactions are those in which the reactants absorb energy in order to continue the reaction. Energy is required and absorbed in this kind of reaction because the reactant energy is lower than the product energy.
Reactant energy and product energy
Example: Process of Photosynthesis, where plants absorb sunlight in the presence of carbon dioxide and water and make their food in the form of glucose and release oxygen.
10. Why is respiration considered an exothermic reaction? Explain.
Answer:
Reactions that release heat are known as exothermic reactions. Because the energy of the reactants is higher than the energy of the products, energy is created throughout these reactions. The process through which our body’s glucose and the oxygen in our cells mix to provide us energy is called respiration. As a result of the breakdown of glucose during the digestive process, which gives us energy together with oxygen, respiration is an exothermic activity.
The reaction that happens is as follows:
11. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer: A single reactant splits into two or more simpler products in a decomposition process.
Example: Decomposition of calcium carbonate to give calcium oxide and carbon dioxide as,
A combination reaction consists of two reactants that combine or mix together to form a single product.
Example: Combination of Calcium oxide and carbon dioxide to form one single product calcium carbonate
Hence, decomposition reactions are the opposite of combination reactions.
12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer: Reactions known as decomposition occur when a reactant splits into two or more products.
a) Decomposition by heat:
Ferrous sulphate decomposes to give ferrous oxide, sulphur dioxide and sulphur trioxide as,
b) Decomposition by light:
Silver chloride decomposes in light to form silver and chlorine as,
c) Decomposition by electricity:
Water decomposes in presence of electricity to form hydrogen and oxygen gases as,
13. What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer: When a more reactive element pushes out a less reactive element from its compound, it’s called a displacement reaction. In the activity sequence, the items at the top might take the place of the elements at the bottom.
Example: Zinc is more reactive than copper and replaces copper from copper sulphate as:
Double displacement reaction is the type of reaction where two compounds react in the way that there is exchange of positive and negative ions and new compounds are formed as products.
Example: On mixing sodium sulphate solution with barium chloride solution, a white precipitate of barium sulphate is formed as:
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:
The equation of recovery of silver from silver nitrate solution in silver refining is as follows:
Here displacement of silver by copper happens as copper is more reactive than silver.
15. What do you mean by a precipitation reaction? Explain by giving examples.
Answer: A precipitation reaction is the kind of reaction in which the reactants exchange ions to generate an insoluble substance known as a precipitate.
Example 1: On mixing sodium carbonate solution with calcium chloride solution, a white precipitate of calcium carbonate is formed.
Example 2: On mixing sodium sulphate solution with barium chloride solution, a white precipitate of barium sulphate is formed.
16. Explain the following in terms of gain or loss of oxygen with two examples each.
a) Oxidation
Answer:
Oxidation is a sort of reaction that occurs when a substance is exposed to oxygen or an electronegative species, or when hydrogen or a positive species is removed from a substance.
For Example:
CO2+H2→CO+H2OCO2+H2→CO+H2O (Addition of oxygen toH2H2)
2Cu+O2→2CuO2Cu+O2→2CuO (Addition of oxygen to Cu)
b) Reduction
Answer:
Reduction is a sort of reaction in which an electronegative species is removed or hydrogen, or an electropositive species, is added to a molecule.
For Example:
CO2+H2→CO+H2OCO2+H2→CO+H2O (Oxygen is removed fromCO2CO2)
CuO+H2−→ΔCu+H2OCuO+H2→ΔCu+H2O (Oxygen is removed from CuO)
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: Copper (Cu) represents the letter “X,” and copper (II) oxide (CuO) is the black component. When copper and oxygen combine, they produce copper (II) oxide, a black chemical that looks like this:
18. Why do we apply paint on iron articles?
Answer: As a reactive metal, iron may react with both air and moisture. Long-term exposure to air or moisture can cause iron objects to corrode and rust. Therefore, paint is used on iron objects to stop them from rusting and to create a barrier against moisture and air exposure.
19. Oil and fat containing food items are flushed with nitrogen. Why?
Answer:
Products containing oils and fats are perishable and can go bad if they come into contact with oxygen. This is a result of the reactivity of oil and fats, which make them rapidly oxidised when exposed to oxygen. These things are cleansed with nitrogen gas to stop oxidation. Since nitrogen is an inert gas, it does not readily react with fats or oils. Food products containing oils and fats are therefore stored in nitrogen gas-filled packets, which extends their shelf life and prolongs their shelf life.
20. Explain the following terms with one example each.
a) Corrosion
Answer: The process by which a material, usually metal, deteriorates and develops an oxide layer on its surface is known as corrosion. Metals are transformed into their sulphides or hydrated oxides. For example, iron, copper, and silver
b) Rancidity
Answer:
Food products like fats and oils undergo a process called rancidity, which involves oxidation. This is known as rancidity and causes the food item to change in flavour and aroma. For instance, food that has been fried and exposed to air for an extended period of time can alter in flavour and aroma and get rancid.
You can prevent rancidity by:
-Including BHA (butylated tri hydroxy anisole) in the mix of antioxidants
-Store the food items in the refrigerator.
-Food should be stored in sealed containers.
-food packets by adding nitrogen to stop oxidation.
Best NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations
For the Next Poem Solution Click Below
CHAPTER 1 – Chemical Reactions and Equations
CHAPTER 2 – Acid, Bases and Salts
CHAPTER 3 – Metals and Non-metals
CHAPTER 4 – Carbon And Its Compounds
CHAPTER 6 – Control And Coordination
CHAPTER 7 – How do Organisms Reproduce
CHAPTER 8 – Heredity and Evolution
CHAPTER 9 – Light Reflection and Refraction
CHAPTER 10 – The Human Eye and the Colourful World
CHAPTER 12 – Magnetic Effects of Electric Current
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