Class-8th Hydrogen Essential ICSE Chemistry Ch-7 Solutions. We Provide Step by Step Answer of Objective, True False , Short / Long Answer Type of Exercise-7 Hydrogen of Bharti Bhawan Publishers . Visit official Website CISCE for detail information about ICSE Board Class-8.
Class-8th Hydrogen Essential ICSE Chemistry Ch-7 Bharti Bhawan Publishers Solutions
| Board | ICSE |
| Publications | Bharti Bhawan |
| Subject | Chemistry |
| Class | 8th |
| Chapter-7 | Hydrogen |
| Book Name | Essential |
| Topics | Solution of Objective, True False , Fill in the blanks , Short / Long Answer Type Questions |
| Academic Session | 2021-2022 |
Short-Answer Type Questions
(Solutions of Bharti Bhawan Publishers Essential ICSE Chemistry-Hydrogen )
Page 76
Question 1:
Name the lightest element and the lightest gas known.
Answer : Hydrogen is the lightest gas and element and is the most abundant in the universe. It is estimated that 90% of the visible universe is composed of hydrogen. Hydrogen have only one electron. Hydrogen is the main element in the plasma state of stars in the main sequence.
Question 2:
In a reaction, one element displaces another from its compound to forma new compound. What is such a reaction called?
Answer : Such reaction will known as displacement reaction. Explanation: As the reaction suggest, it displace an element and form a new compound.
Question 3:
By which method is hydrogen gas collected? Explain your answer.
Answer : Hydrogen is collected by downward displacement of water as it is less denser than water. Hence it comes out at the surface of water . It is insoluble in water so it does not dissolve in water. In case of displacement with air, it is not possible even if hydrogen is lighter than air (14.5 times lighter than air).
Question 4:
What gases collect at the different electrodes in the electrolysis of acidulated water?
Answer : During electrolysis of acidulated water, hydrogen is collected at cathode and oxygen is collected at the anode.
Question 5:
How many times lighter or heavier than air is hydrogen?
Answer : Hydrogen is lighter than each gas that is present in the air. So when the gases in the air are measured against hydrogen, the latter becomes lighter. Therefore, Hydrogen is 14 times lighter than Air.
Question 6:
When kindled, will hydrogen burn in oxygen? Name the compound formed, if any, and give the balanced equation for the reaction.
Answer : 2H2 + O2 ——–> 2H20
Question 7:
State the conditions under which hydrogen is made to react with nitrogen in the Haber process.
Answer : In the Haber process, nitrogen and hydrogen react together under these conditions: a high temperature – ranging from 350°C to 450°C. a high pressure – ranging from 150 to 200 atmospheres (150 – 200 times normal pressure)
Question 8:
Why is hydrogen considered a clean fuel?
Answer : Hydrogen is a clean fuel that, when consumed in a fuel cell, produces only water, electricity, and heat. … Due to their high efficiency and zero-or near zero-emissions operation, hydrogen and fuel cells have the potential to reduce greenhouse gas emission in many applications.
Question 9:
Give reasons why helium is preferred to hydrogen for filling weather balloons.
Answer : Hydrogen is a inflammable gas and sets fire very easily. Highly combustible gas and may cause severe hazard. So filling the balloons with hydrogen gas is highly unsafe. Therefore, we prefer helium gas instead of hydrogen gas to fill the balloons.
Long-Answer Type Questions
(Solutions of Bharti Bhawan Publishers Essential ICSE Chemistry-Hydrogen )
Page 77
Question 1:
Describe how hydrogen is prepared in the laboratory. Explain why nitric acid is not used in the process.
Answer : 2HNO3 →2NO2 + H2O + [O] and it oxidises the hydrogen formed to water. That is why, Nitric Acid cannot be used for preparation of hydrogen gas. However, metals like Magnesium and Manganese still produce Hydrogen Gas. Only 1% dilute and cold nitric acid reacts with magnesium and manganese to liberate Hydrogen gas.
Question 2:
Give three examples to show that hydrogen is a reducing agent
Answer : Hydrogen donates its electrons to reduce other substances. 1) Hydrogen reduces acetylene (OS=-1) to ethane (OS=-3). 2) Hydrogen reduces bromine (OS=0) to hydrobromic acid (OS=-1). 3) Hydrogen reduces oxygen (OS=0) to water (OS=-2).
Question 3:
Write a note on the oxyhydrogen flame.
Answer : OXYHYROGEN FLAME , the flame attending the combustion of hydrogen and oxygen , and characterized by a very high high temperature . Hydrogen gas readily burns in oxygen or air with the formation of water . The quantity of heat evolved according to Julius Thomsen , is 34 , 116 calories for each gram of hydrogen burned.
Objective Type Questions
(Solutions of Bharti Bhawan Publishers Essential ICSE Chemistry-Hydrogen )
Page 77
Choose the correct option.
1. Which of the following pairs of elements will react to give a gas that dissolves in water to form an acid
(a) Hydrogen and Oxygen
(b) Hydrogen and chlorine
(c) Hydrogen and nitrogen
(d) None of these
Answer :(b) Hydrogen and chlorine
2. With which of the following elements will hydrogen react to give a gas that smells like rotten eggs?
(a) Oxygen
(b) Chlorine
(c) Sulphur
(d) Nitrogen
Answer :(c) Sulphur
3. Which among the following metals reacts with water most vigorously?
(a) Sodium
(b) Magnesium
(d) Iron
(c) Zinc
Answer 🙁 a) Sodium
4. Which of the following metals will not displace hydrogen from water?
(a) Sodium
(b) Potassium
(c) Calcium
(d) Copper
Answer : (d) Copper
Fill in the Blanks.
1. A reactive metal like potassium, sodium or calcium displaces….hydrogen .. room water. (hydrogen / oxygen)
2. Complete the following equations and balance them.
(a) Zn + HCI –> ZnCl2 + H2
(b) Fe + H2SO4 (dilute) –>FeSO4(aq) + H2 (g)
(c) CuO + ..H2. —> Cu + H2O
(d) Fe + H2O –> Fe3O2 + ….H2
(e) H2O + Zn → H2 + ZnO
3. Iron oxide is ….. reduced.….. by hydrogen to iron. (oxidised/ reduced)
4. Magnesium reacts with steam to form ….magnesium oxide…. and …..hydrogen.…. (magnesium oxide/magnesium hydroxide/oxygen/hydrogen)
5. The removal of hydrogen from a substance is called …..oxidation…….. (oxidation/reduction)
Write T for true and F for false for the following statements.
1. Hydrogen is usually found in the free state F
2 The addition of oxygen to a substance is called reduction. F
3. The removal of oxygen from a substance is called reduction. T
4. Hydrogen can be used as a fuel. T
5. Helium is preferred to hydrogen for filling balloons. T
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