Selina Concise Class 8 Chemistry Solution Chapter No. 7- ‘Hydrogen’ For ICSE Board Students.
Exercise -I:
1)
a) Hydrogen is ………………. than air .
Answer : lighter
Explanation: Hydrogen is first element in periodic table it has one proton in Nucleus and one electron in orbit . It most lighter than air.
b) Hydrogen is ………………… soluble in water .
Answer : sparingly
Explanation: Hydrogen is non polar and water is Polar that’s why hydrogen is sparingly soluble in water.)
c) Hydrogen burns with a ……………..flame and ………….sound is heard.
Answer: Blue and pop.
Explanation: Hydrogen burns in a air presence oxygen with blue flame form and pop sound is heard.)
d) A metal ………………hydrogen in the reactivity series gives hydrogen with ……………
Answer : above , Water
Explanation: When a metal above the hydrogen reactivity series react with water to gives Hydrogen )
e) Hydrogen react with metal oxide to form ……….. and………..
Answer : metal and water
When hydrogen chemically react with metal oxide to form a metal and water.
f) Oxidation is removal of …………or addition of…………….
Answer : Hydrogen and Oxygen
Explanation: Oxidation is a process in which hydrogen is removed and oxygen is added in a substance.
g) In redox reaction , oxidation and reduction occur ……………
Answer : simultaneously
Explanation: Redox reaction is a type of chemical reaction in which oxidation and reduction occur simultaneously that is one compound is reduced and other get oxidised.
2)
a)
Answer : False
b)
Answer :True
c)
Answer : False
d)
Answer : True
e)
Answer : True
f)
Answer : False
g)
Answer : False
3) a)
Answer : H₂ + Cl₂ → 2HCl
b)
Answer : H₂ + S → H₂S
c)
Answer :Zn + 2HCl → ZnCl₂ + H₂
d)
Answer :CuO + H₂ → Cu + H₂O
e)
Answer : 3Fe + 4H₂O → Fe₃O₄ + 4H₂
f)
Answer : 2K + 2H₂O → 2KOH + H₂
4)
a)
Answer : Hydrogen can be used as a fuel because hydrogen has high energy as fuel , it is clean fuel when hydrogen burns it is almost produce no pollution .
b)
Answer : Though hydrogen is lighter than air it can not be collected by downward displacement air, because hydrogen easily mix with air due to lightness , and oxidised with air presence oxygen so it is not collected by downward displacement of air .
c)
Answer : A pop sound is produced when hydrogen gas is burnt because it contains lots gasses mixture , hydrogen, oxygen ,water vapour,etc due to this impurities presence in hydrogen , when it burn small explosion occur and produce pop sound.
d)
Answer: Helium is replaced hydrogen in whether observation balloons because hydrogen is High reactive with air presence oxygen , if hydrogen balloons burst it can exploded if come in contact with oxygen that’s of helium is replaced by hydrogen balloons.
e)
Answer : Nitric acid is not used for the preparation of hydrogen gas because Nitric Acid strong oxidising agent and when it react with hydrogen it will oxidised and convert into a water
5) a)
Answer: Potassium (K) and Sodium (Na) metals give hydrogen with cold water.
b)
Answer : Iron is a metal which liberate hydrogen only when steam is passed over red hot metal .
c)
Answer : Oxidation is the process in which oxygen is added or hydrogen is removed.
d)
Answer :Copper oxide (CuO) is a metallic oxide which can be reduced into metal by hydrogen.
6) a)
Answer : Granulated Zinc (Zn) and dilute sulphuric (dil. H2SO4) or Magnesium (Mg) and dilute Sulphuric acid (dil. H2SO4).
b)
c)
Answer : Hydrogen gas is collected by downward displacement of water method because due to this method water present in a glass trough over it inverted gas jar is present , water is displace and hydrogen gas bubbles liberated this gas bubbles collect in gas jar which is inverted on glass trough.
7) a)
Answer: Take a filled hydrogen gas jar and put it inverted or downward on lighted candle , and pack this place such as hydrogen not leaked by this jar , we will see that candle supress or extinguished but the gas is burn and produce pop sound, by this experiment show that hydrogen gas is non supporter of combustion .
b)
Answer : Take a bottle fill with zinc metal granules , and dilute hydrochloric acid , and flat glass dish fill with soap solution , put a delivery tube one end in bottle and other one in soap solution dish , chemical reaction takes place between Zinc granules and dilute hydrochloric acid to form Hydrogen gas , this hydrogen gas go into a soap solution through delivery tube , in a soap solution , bubbles of soap solution containing hydrogen gas goes upward direction , So rising this bubbles in upward direction show that the hydrogen gas is lighter than air.
8)
Answer : Hydrogen is a good reducing agent , like when hydrogen gas is react with copper , iron ,lead metallic oxide it will reduce or remove oxygenfrom this metallic oxide , and separate the metal .
For Example :. When copper oxide react with hydrogen gas , copper oxide reduce oxygen form copper and hydrogen oxidised and convert into water.
9)
a) .
Answer : Hydrogen gas is manufactured by Bosch process .
b) .
Answer : i.) When steam of water and carbon (red hot coke) chemically react with each other under 1000°C to form a mixture of carbon monoxide and hydrogen also known as water gas mixture . During this reaction energy is absorbed so this is endothermic reaction.
ii) . When a gas water mixture again react with another steam of water in presence of catalyst Ferric oxide or chromium trioxide to form carbon dioxide, hydrogen gas and heat is released that’s of it is exothermic reaction.
c)
Answer : Hydrogen gas is separate from carbon dioxide and carbon monoxide from following reactions.
i) When a product carbon dioxide and hydrogen pass through under pressure of water by this process carbon dioxide is dissolved and hydrogen is separate , this carbon dioxide can separate when it react chemically with potassium hydroxide (KOH)
2KOH + CO₂ → K ₂CO₃ + H₂O
Potassium Carbon. Potassium. Water
Hydroxide. Dioxide. Carbonate
ii) Carbon monoxide is separate through gases pass ammoniacal cuprous chloride during this reaction carbon monoxide is dissolved and leave hydrogen
CuCl + CO + 2H₂O → CuCl.CO.2H₂O
10)
Sr.No | Column A | Column B |
1 | A metal which react with cold water to form Hydrogen | 1. Sodium |
2 | A gas which inflammable and a non supporter of combustion | 2. Hydrogen |
3 | A process in which Vanaspati ghee is prepared from Vegetable oils. | 3. Hydrogenation |
4 | The removal of hydrogen or addition of oxygen | 4. Oxidation |
5 | The addition of hydrogen or removal of oxygen. | 5. Reduction |
11)
Answer : Following are uses of hydrogen .
1) Hydrogen used as fuel.
2) Hydrogen used hydrogenation of vegetables oil.
3) Hydrogen used for preparation fertilizer , chemicals , urea , hydrochloric acid etc.
4) Hydrogen used for the extraction of less reactive metal as compared to hydrogen.
5) Hydrogen used for preparation of meteorological instruments which go into air.
12)
a)
Answer: Catalytic hydrogenation
Catalytic hydrogenation is the process in which hydrogen gas is treated with Vanaspati oil in the presence of catalyst such as Ni, Pt, Pd etc to change it into ghee .
b)
Answer: Oxidation
Oxidation is the process by with oxygen is added in the molecules or hydrogen is removed from the substance or molecules.
c)
Answer : Reduction
Reduction is the process in which hydrogen is added in the molecules or oxygen is removed from the substance or molecules.
d)
Answer : Redox reaction.
Redox reaction is a chemical reaction in which both oxidation and reduction occur simultaneously like one substance is oxidised and other one is reduced.
13)
a)
Answer : Hydrogen chloride
(When equal volume of hydrogen gas and chlorine gas react direct to sunlight it will diffused and produced hydrogen chloride or hydrochloric acid)
b)
Answer : Calcium
(When active metal like calcium react with cold water it will liberate and produced metallic oxide and hydrogen gas)
c)
Answer : top
(In reactivity series more reactive metal are placed in the top )
d)
Answer : all of the above
(Hydrogen is used for the preparation of fertilizer , hydrogenated oil, heat and light , chemicals , urea , Ammonium etc.)
e)
Answer : neither supporter nor combustible
(Hydrogen gas is non supporter of combustible it is extinguished the fire but gas
f)
Answer : carbon monoxide and hydrogen
(Water gas is mixture of carbon monoxide and hydrogen , it will form in the Bosch process for manufacturing of hydrogen gas).