Chapter 2:- Periodic Classification of Element
Chapter 3:- Chemical Reaction and Equation
Chapter 4:- Effect of Electric Current
Chapter 5 :- Heat
Chapter 6 Refraction of Light
Chapter 7:- Lenses
Chapter 8 :- Metallurgy
Chapter 9 Carbon Compound
Chapter 10 :- Space Mission
Textbook Exercise Solution
1. Choose the correct option from the bracket and explain the statement giving reason.(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, decomposition)
a. To prevent rusting, a layer of …….. metal is applied on iron sheets.
Answer:- Zinc
Explanation:- Layer of zing prevent rusting because it is non corrosive
b. The conversion of ferrous sulphate to ferric sulphate is …….. reaction.
Answer:-
The conversion of ferrous sulphate to ferric suphate is an oxidation Reaction
Oxidation reaction means addition of oxygen. or removal of electron While converting from ferrous to ferric sulphate one electron is removed from ferrous and it becomes ferric suplhate.
c. When electric current is passed through acidulated water …….. of water takes place.
Answer:- When electric current is passed
through acidulated water electrolysis of
water takes place.
Explanation:- When an electric current is passed through acidulated water, it will produce electrolysis. During this process, water is decomposed into hydrogen and oxygen. The positive ions with some move to the cathode while the negative ions will also move to the anode. Hydrogen gas will form at the cathode
d. Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 form a white precipitate is an example of ……. reaction.
Answer:_ Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 form a white precipitate is an example of Double Displacement reaction.
BaCl 2 (Barium chloride)+ ZnSO 4 (Zinc sulphate) → ZnCl 2 (Zinc chloride) + BaSO 4 (Barium sulphate.)
Here Zinc and Barium both displaces each other. that is why it is called double displacemet reaction.
2. Write answers to the following.
a. What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Answer:-
The process in which oxidation and reduction reaction takes place simultaneously is called redox reaction.
Oxidation :- Gain of oxygen is called oxidation
Reduction :- Loss of oxygen is called reduction.
BaCl 2 (Barium chloride)+ ZnSO 4 (Zinc sulphate) → ZnCl 2 (Zinc chloride) + BaSO 4 (Barium sulphate.)
Here znso4 is loosing oxygen hence it is reducing and Barium is gaining oxygen hence it is oxydising.
b. How can the rate of the chemical reaction, namely, decomposition of hydrogen peroxide be increased?
Answer:-
The rate of decomposition of hydrogen peroxide can be increased by having the reaction occurs in the presence of iodide ion. The reaction is proceeded by a two-step mechanism:
Step 2: IO-(aq) + H2O2(aq) → H2O (l) + O2(g) + I-(aq)
c. Explain the term reactant and product giving examples.
Reactant: The substance which take part in a chemical reaction are called reactants.
Product: the substance which forms as a result of chemical reaction is called products.
Consider following reaction
BaCl 2 (Barium chloride)+ ZnSO 4 (Zinc sulphate) → ZnCl 2 (Zinc chloride) + BaSO 4 (Barium sulphate.)
Here Barium chloride and zinc suphate are reactant and zinc chloride and barium suphate is product
d. Explain the types of reaction with reference to oxygen and hydrogen. Illustrate with examples.
Answer:-
1.Combination Reaction
When two atoms react to form a compound, it is know as combination reaction.
For example: \[2 H_2 + O_2 \to 2 H_2 O\]
When a compound breaks into simple molecular substances from which it is made up of, it is know as decomposition reaction.
For example: \[2 H_2 O \to 2 H_2 + O_2\]
Oxidation:
(i) The addition of oxygen to a substance is called oxidation.
(ii) The removal of hydrogen to a substance is called oxidation.
Reduction:
(i) The addition of hydrogen to a substance is called reduction.
(ii) The removal of oxygen to a substance is called reduction.
For example: CuO + H2 ------> Cu + H2 O]
e. Explain the similarity and difference in two events, namely adding NaOH to water and adding CaO to water.
Answer:-
Similarity :
Both NaOH and CaO, when dissolved separately in water, solid NaOH dissolves releasing heat, resulting in rise in temperature.
This reaction is exothermic reaction. When solid CaO dissolves in water, Ca(OH)2 is formed, large amount of heat is evolved.
This reaction is also exothermic reaction. Both reactions are combination reactions and single product is obtained.
NaOH(s) + H2O → NaOH(aq) + Heat CaO(s) + H2O → Ca(OH)2(aq) + Heat
Difference:
1. Aqueous solution of NaOH is considered as a strong alkali.
2. Aqueous solution of Ca(OH)2 is considered as a weak alkali.
3. Explain the following terms with examples.
a. Endothermic reaction
Answer:-
An endothermic reaction is a chemical reaction that requires or absorbs energy from its surroundings. In other words, the reaction takes in heat from its surroundings to proceed. The energy is typically supplied in the form of heat, but it can also be supplied by other means such as electricity or light.
An example of an endothermic reaction is the reaction between baking soda (sodium bicarbonate) and vinegar (acetic acid). When baking soda and vinegar are mixed, they undergo a chemical reaction that produces carbon dioxide gas, water, and sodium acetate. This reaction is endothermic because it absorbs heat from the surroundings, causing the temperature to decrease. The reaction can be represented by the following equation:
NaHCO3 (s) + CH3COOH (aq) → CO2 (g) + H2O (l) + NaCH3COO (aq)
In this reaction, the carbon dioxide gas bubbles that are formed cause the mixture to froth and expand. The reaction is commonly used in baking to leaven bread and other baked goods, as the carbon dioxide gas helps the dough rise.
b. Combination reaction
Answer:-
Combination reaction:
Those reactions in which two or more substances combine to form single substance is called combination reaction
For example : Magnesium and oxygen combine, when heated, to form magnesium oxide.
c. Balanced equation
Answer:-
A balanced equation is a chemical equation in which the number of atoms of each element on the reactant side is equal to the number of atoms of the same element on the product side. This is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.
For example, the balanced equation for the reaction between hydrogen gas and oxygen gas to form water is:
2H2 + O2 -> 2H2O
In this equation, there are four hydrogen atoms and two oxygen atoms on the reactant side, and the same number of hydrogen and oxygen atoms on the product side. This means that the equation is balanced, and the law of conservation of mass is satisfied.
d. Displacement reaction
Answer:-
A displacement reaction is a chemical reaction in which an element displaces another element from a compound, producing a new compound and a new element. The displaced element is usually a less reactive element, while the displacing element is more reactive.
A suitable example of a displacement reaction is the reaction between zinc metal and hydrochloric acid to produce zinc chloride and hydrogen gas. The balanced chemical equation for this reaction is:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
In this reaction, the zinc metal displaces the hydrogen from the hydrochloric acid to form zinc chloride and hydrogen gas. Zinc is more reactive than hydrogen and can displace it from the compound.
4. Give scientific reasons.
a When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky.
Answer:-
When the gas formed on heating limestone, which is mainly composed of calcium carbonate (CaCO3), is passed through freshly prepared lime water, the lime water turns milky. This is because the gas formed on heating limestone is carbon dioxide (CO2), which reacts with the calcium hydroxide (Ca(OH)2) in the lime water to form calcium carbonate, which is insoluble and appears as a milky precipitate:
Ca(OH)2 + CO2 → CaCO3 + H2O
This reaction is used as a test for the presence of carbon dioxide gas.
b. It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly.
Answer:-
This observation can be explained based on the surface area of the Shahabad tile pieces and powder. When a substance is in contact with a solution, the reaction can only take place at the surface of the substance. The greater the surface area, the faster the reaction will occur.
In the case of Shahabad tile pieces, they have a smaller surface area compared to the Shahabad tile powder. Therefore, the reaction between the HCl and the Shahabad tile pieces will be slower as only a small surface area is exposed to the acid at a time. On the other hand, the Shahabad tile powder has a larger surface area and hence more of it is in contact with the HCl at a time, leading to a faster reaction.
Hence, the Shahabad tile powder disappears rapidly compared to the Shahabad tile pieces when reacted with HCl.
c.While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring.
Answer:-
While preparing dilute sulfuric acid from concentrated sulfuric acid in the laboratory, the concentrated acid is added slowly to water with constant stirring to avoid a violent exothermic reaction. When water is added to concentrated sulfuric acid, the heat generated due to the reaction may cause the mixture to splash out, causing severe burns and damage to the surroundings. By adding the concentrated acid to water slowly, the heat generated is dissipated more effectively and the risk of splashing is minimized. This is a safety precaution and should always be followed while handling concentrated sulfuric acid.
d. It is recommended to use air tight container for storing oil for long time.
Answer:-
It is recommended to use an airtight container for storing oil for a long time because oil is easily oxidized in the presence of air. Oxidation causes oil to become rancid and develop an unpleasant odor and taste. This is due to the reaction of oil with oxygen in the air, which leads to the formation of free radicals and various oxidative products. The use of an airtight container prevents the entry of air and helps to preserve the quality and freshness of the oil for a longer time.
5. Observe the following picture a write down the chemical reaction with explanation.
6. Identify from the following reactions the reactants that undergo oxidation and reduction.
a. Fe + S FeS
Answer:-
Iron (Fe) undergoes oxidation and Sulphur (S) undergoes reduction.
b. 2Ag2O 4 Ag + O2
Answer:-
In a reaction, silver oxide is changing to silver. That is, oxygen is being removed from silver oxide. Removal of oxygen from substance is called reduction, so silver oxide undergoes reduction.
c. 2Mg + O2 —–>2MgO
Answer:-
In a reaction, magnesium is changing to magnesium oxide. That means, oxygen is being added to magnesium. Addition of oxygen to a substance is called oxidation, so magnesium undergoes oxidation.
d. NiO + H2 Ni + H2O
Answer:-
In a reaction, Nickle oxide is changing to nickle. That is, oxygen is being removed from nickle oxide. Removal of oxygen from substance is called reduction, so nickle oxide undergoes reduction.In a reaction, hydrogen is changing to H2O. That is, oxygen is being added to hydrogen. Addition of oxygen to a substance is called oxidation, so hydrogen undergoes oxidation.
7. Balance the following equation stepwise
a. H2S2O7(l) + H2O(l)—–> H2SO4(l)
Answer:-
| Elements | No. of atoms in the reactant |
| H | 4 |
| S | 2 |
| O | 8 |
Step 2: Count the number of each atom on the product side:
| Elements | No. of atoms in the product |
| H | 2 |
| S | 1 |
| O | 4 |
Step 3: Number of atoms of elements on both side is not the same.
If we multiply the product side by 2, then the number of atoms in the product and reactant side gets balanced.
| Elements | No. of atoms in the reactant | No. of atoms in the product |
| H | 4 | 2 × 2 = 4 |
| S | 2 | 1 × 2 = 4 |
| O | 8 | 4 × 2 = 8 |
b. SO2(g) + H2S(aq) S(s) + H2O (l)
Answer:-
SO2(g) + H2S(aq) → S(s) + H2O(l)
Step1: Count the number of each atom in reactant side:
H = 2
S = 2
O = 2
Step 2: Count the number of each atom in product side:
H = 2
S = 1
O = 1
Step 3: Then balance the number of each atom in an equation by multiplying reactant and product side with numeral value:
If we multiply H2S by 2 in the reactant side and S by 3 and H2O by 2 on the product side, the number of atoms in the product and reactant side gets the balance.
SO2(g) + 2H2S(aq) → 3S(s) + 2H2O(l)
c. Ag(s) + HCl(aq) ——>AgCl + H2
Answer:-
Ag(s) + HCl(aq) → AgCl ↓+ H2 ↑
Step1. Count the number of each atom in reactant side:
H= 1
Ag=1
Cl=1
Step2. Count the number of each atom in product side:
H= 2
Ag=1
Cl=1
Step3.Then balance the number of each atom in an equation by multiplying reactant and product side with numeral value:
If we multiply Ag by 2 and HCl by 2 in the reactant side and AgCl by 2 in the product side, then number of atoms in product and reactant side gets balance.
2Ag(s) + 2HCl(aq) → 2AgCl ↓+ H2 ↑
d. NaOH (aq) + H2SO4(aq) Na2SO4(aq) + H2O(l)
Answer:-
NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + H2O(l)
Step1. Count the number of each atom in reactant side:
Na= 1
H=3
O=5
S=1
Step2. Count the number of each atom in product side:
Na= 2
H=2
O=5
S=1
Step3.Then balance the number of each atom in an equation by multiplying reactant and product side with numeral value:
If we multiply NaOH by 2 in the reactant side and H2O by 2 in the product side, then number of atoms in product and reactant side gets balance.
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) +2H2O(l)
8. Identify the endothermic and exothermic reaction.
a. HCl + NaOH ——->NaCl + H2O + heat
c. CaO + H2O ——->Ca(OH)2 + heat
Answer:-
Here heat is liberated thats why it is exothermic reaction
b. 2KClO3(s) ——>2KCl(s) + 3O2
d. CaCO3(s)—–> CaO(s) + CO2
Answer:_ In this decomposition reaction heat is supplied for the reaction therefore it is endo thermic reaction.
9. Match the column in the following table.
| Reactants | Products | Type of chemical reaction |
|---|---|---|
| BaCl2(aq) + ZnSO4(aq) | H2CO3(aq) | Displacement |
| 2AgCl(s) | FeSO4(aq) + Cu(s) | Combination |
| CuSO4(aq) + Fe(s) | BaSO4↓ + ZnCl2(aq) | Decomposition |
| H2O(l) + CO2(g) | 2Ag(s) + Cl2(g) | Double displacement |
Answer:_
| Reactants | Products | Type of chemical reaction |
|---|---|---|
| BaCl2(aq) + ZnSO4(aq) | BaSO4↓ + ZnCl2(aq) | Double displacement |
| 2AgCl(s) | 2Ag(s) + Cl2(g) | Decomposition |
| CuSO4(aq) + Fe(s) | FeSO4(aq) + Cu(s) | Displacement |
| H2O(l) + CO2(g) | H2CO3(aq) | Combination |