Exercise
1. Fill in the blanks:
(a) Hydrogen is __________ than air.
(b) Hydrogen is __________ soluble in water.
(c) Hydrogen bums with a __________ flame and __________ sound is heard.
(d) A __________ hydrogen in the reactivity series gives hydrogen with water.
(e) Hydrogen reacts with metal oxides to form __________ and __________.
(f) Oxidation is the removal of __________ and addition of oxygen.
(g) In redox reaction oxidation and reduction occur __________.
Answer:
(a) Hydrogen is lighter than air.
(b) Hydrogen is sparingly soluble in water.
(c) Hydrogen bums with a oxyhydrogen pale blue flame and pop sound is heard.
(d) A metal sodium hydrogen in the reactivity series gives hydrogen with water.
(e) Hydrogen reacts with metal oxides to form metal and water.
(f) Oxidation is the removal of hydrogen and addition of oxygen.
(g) In redox reaction oxidation and reduction occur simultaneously.
2. Indicate which of the following statements are true and which are false:
(a) Hydrogen molecule is monovalent.
(b) The removal of hydrogen from a substance is called reduction.
(c) Nitric acid cannot be used to prepare hydrogen by its action on active metals?
(d) The reaction between hydrogen and nitrogen to form ammonia is reversible.
(e) Zinc can liberate hydrogen from water, acid and alkali solution.
(f) Hydrogen is combustible as well as a supporter of combustion.
(g) Hydrogen gas is easily liquefiable.
Answer:
(a) Hydrogen molecule is monovalent. (a) False
(b) The removal of hydrogen from a substance is called reduction. (b) True
(c) Nitric acid cannot be used to prepare hydrogen by its action on active metals. (c) False
(d) The reaction between hydrogen and nitrogen to form ammonia is reversible. (d) True
(e) Zinc can liberate hydrogen from water, acid and alkali solution. (e) True
(f) Hydrogen is combustible as well as a supporter of combustion. (f) False
(g) Hydrogen gas is easily liquefiable. (g) False
3. Complete and balance the following equations:
(a) H2 + ______ → 2HCl
(b) H2 + S → _________
(c) Zn + _________ → ZnCl2 + H2
(d) CuO + ________ → Cu + _________.
(e) Fe +H2O → ________ + _________.
(f) K + H2O → _______ + ________.
Answer:
(a) H2 + Cl2 → 2HCl
(b) H2 + S →H2S
(c) Zn + 2HCl → ZnCl2 + H2
(d) CuO + H2 → Cu + _________.
(e) Fe + 4H2O → Fe3O4 + 4H2.
(f) 2K + 2H2O → 2KOH + H2.
4. Give reasons for the following:
(a) Hydrogen be used as a fuel?
(b) Though hydrogen is lighter than air it cannot be collected by downward displacement of air.
(c) A pop sound produced when hydrogen is burnt?
(d) Helium replaced hydrogen in weather observation balloons?
(e) Nitric acid not used for the preparation of hydrogen gas?
Answer:
(a) Important fuels include liquid hydrogen, water gas, and coal gas.
(b) Because hydrogen weighs less than air. By forcing the air downward, the gas can be collected. However, doing so is unsafe since hydrogen and air mixture can explode.
(c) Impure hydrogen gas burbles in the air. This occurs as a result of the contaminants that are present in it.
(d) A hydrogen leak in a balloon can cause an explosive mixture of hydrogen and air to occur. Helium has taken the place of hydrogen.
(e) Nitric acid cannot produce hydrogen by reacting with metals since it also produces nitrous oxide and nitric oxide, which oxidise hydrogen to produce water.
5. Name the following:
(a) Two metals which give hydrogen with cold water.
(b) A metal which liberates hydrogen only when steam is passed over red hot metal.
(c) The process in which oxygen is added or hydrogen is removed.
(d) A metallic oxide which can be reduced into metal by hydrogen.
Answer:
(a) Sodium (Na) and Potassium (K) give hydrogen with cold water.
(b) Iron
(c) Oxidation
(d) Copper oxide (CuO)
6. (a) Name the chemicals required to prepare hydrogen gas in the laboratory.
(b) Give a balanced chemical equation for the reaction.
(c) Draw a neat and well-labelled diagram for the laboratory preparation of hydrogen.
(d) How is hydrogen gas collected?
Answer:
(a) Hydrochloric acid with granulated zinc.
(b) ZnCl2 + H2 → Zn + 2HCl (g)
(c)
Exercise
1. Fill in the blanks:
(a) Hydrogen is __________ than air.
(b) Hydrogen is __________ soluble in water.
(c) Hydrogen bums with a ¬¬¬¬¬¬__________ flame and __________ sound is heard.
(d) A __________ hydrogen in the reactivity series gives hydrogen with water.
(e) Hydrogen reacts with metal oxides to form __________ and __________.
(f) Oxidation is the removal of __________ and addition of oxygen.
(g) In redox reaction oxidation and reduction occur __________.
Answer:
(a) Hydrogen is lighter than air.
(b) Hydrogen is sparingly soluble in water.
(c) Hydrogen bums with a oxyhydrogen pale blue flame and pop sound is heard.
(d) A metal sodium hydrogen in the reactivity series gives hydrogen with water.
(e) Hydrogen reacts with metal oxides to form metal and water.
(f) Oxidation is the removal of hydrogen and addition of oxygen.
(g) In redox reaction oxidation and reduction occur simultaneously.
2. Indicate which of the following statements are true and which are false:
(a) Hydrogen molecule is monovalent.
(b) The removal of hydrogen from a substance is called reduction.
(c) Nitric acid cannot be used to prepare hydrogen by its action on active metals?
(d) The reaction between hydrogen and nitrogen to form ammonia is reversible.
(e) Zinc can liberate hydrogen from water, acid and alkali solution.
(f) Hydrogen is combustible as well as a supporter of combustion.
(g) Hydrogen gas is easily liquefiable.
Answer:
(a) Hydrogen molecule is monovalent. (a) False
(b) The removal of hydrogen from a substance is called reduction. (b) True
(c) Nitric acid cannot be used to prepare hydrogen by its action on active metals. (c) False
(d) The reaction between hydrogen and nitrogen to form ammonia is reversible. (d) True
(e) Zinc can liberate hydrogen from water, acid and alkali solution. (e) True
(f) Hydrogen is combustible as well as a supporter of combustion. (f) False
(g) Hydrogen gas is easily liquefiable. (g) False
3. Complete and balance the following equations:
(a) H2 + ______ → 2HCl
(b) H2 + S → _________
(c) Zn + _________ → ZnCl2 + H2
(d) CuO + ________ → Cu + _________.
(e) Fe +H2O → ________ + _________.
(f) K + H2O → _______ + ________.
Answer:
(a) H2 + Cl2 → 2HCl
(b) H2 + S →H2S
(c) Zn + 2HCl → ZnCl2 + H2
(d) CuO + H2 → Cu + _________.
(e) Fe + 4H2O → Fe3O4 + 4H2.
(f) 2K + 2H2O → 2KOH + H2.
4. Give reasons for the following:
(a) Hydrogen be used as a fuel?
(b) Though hydrogen is lighter than air it cannot be collected by downward displacement of air.
(c) A pop sound produced when hydrogen is burnt?
(d) Helium replaced hydrogen in weather observation balloons?
(e) Nitric acid not used for the preparation of hydrogen gas?
Answer:
(a) Important fuels include liquid hydrogen, water gas, and coal gas.
(b) Because hydrogen weighs less than air. By forcing the air downward, the gas can be collected. However, doing so is unsafe since hydrogen and air mixture can explode.
(c) Impure hydrogen gas burbles in the air. This occurs as a result of the contaminants that are present in it.
(d) A hydrogen leak in a balloon can cause an explosive mixture of hydrogen and air to occur. Helium has taken the place of hydrogen.
(e) Nitric acid cannot produce hydrogen by reacting with metals since it also produces nitrous oxide and nitric oxide, which oxidise hydrogen to produce water.
5. Name the following:
(a) Two metals which give hydrogen with cold water.
(b) A metal which liberates hydrogen only when steam is passed over red hot metal.
(c) The process in which oxygen is added or hydrogen is removed.
(d) A metallic oxide which can be reduced into metal by hydrogen.
Answer:
(a) Sodium (Na) and Potassium (K) give hydrogen with cold water.
(b) Iron
(c) Oxidation
(d) Copper oxide (CuO)
6. (a) Name the chemicals required to prepare hydrogen gas in the laboratory.
(b) Give a balanced chemical equation for the reaction.
(c) Draw a neat and well-labelled diagram for the laboratory preparation of hydrogen.
(d) How is hydrogen gas collected?
Answer:
(a) Hydrochloric acid with granulated zinc.
(b) ZnCl2 + H2 → Zn + 2HCl (g)
(c)
(d) Hydrogen gas is gathered by forcing water downward.
7. How would you show that hydrogen:
(a) Is a non-supporter of combustion?
(b) Is lighter than air?
Answer:
(a) Place the opening of a jar filled with hydrogen gas downward. Put a lit candle inside the container. The gas bursts with a pop , but the flame is put out. This demonstrates that hydrogen doesn’t support combustion.
(b) As shown in the picture, take a delivery tube and dip one end into a soap solution kept in a trough and the other into a jar with a flat bottom. Hydrogen-containing soap bubbles ascend into the air. Hydrogen is lighter than air, as evidenced by the rising soap bubbles.
The fact that hydrogen is lighter than air is demonstrated by hydrogen-filled soap bubbles floating upward in the soap solution and into the atmosphere.
8. Hydrogen is a good reducing agent: What do you understand by the above statement? Explain with the help of copper oxide as an example.
Answer:
When hydrogen gas is run over heated metallic oxides of copper, lead, iron, etc., it eliminates oxygen from them and reduces them to the corresponding metal, acting as a good reducing agent.
Take each of the following examples where metallic oxide and hydrogen react. Metal oxides act as oxidising and reducing agents, respectively.
9. (a) Name a process by which hydrogen gas is manufactured.
(b) Give equations for the reactions’) How is hydrogen separated from carbon dioxide and carbon monoxide?
Answer:
(a) The Bosch technique is used to prepare hydrogen for commercial use.
(b) In a furnace known as a converter, hot coke is carried through with steam at a temperature of 1000°C. As a result, water gas, a mixture of carbon monoxide and hydrogen gases, is created. The nature of this reaction is endothermic.
(ii) Water gas is combined with surplus steam and fed via chromium trioxide and ferric oxide (Fe2O3) catalysts (Cr2O3). He has an exothermic reaction.
(c) The end results are carbon dioxide, hydrogen, and some unreacted carbon monoxide. By forcing the combination through water under pressure, where carbon dioxide dissolves and leaves hydrogen behind, hydrogen is separated from carbon dioxide. By putting carbon dioxide through a caustic potash (KOH) solution, carbon dioxide can also be separated.
2KOH + CO2 → K2CO3 + H2O
(ii) To separate carbon monoxide the gaseous mixture is passed through ammoniacal cuprous chloride in which carbon monoxide dissolves leaving behind hydrogen. Thus hydrogen gas is obtained.
CuCl + CO 2H2O → CuCl.CO.2H2O
Addition product
Answer:
11. State four uses of hydrogen:
Answer:
Below are the four uses of hydrogen:-
1. Oxy-hydrogen flames, created when hydrogen and oxygen combine, are used for cutting and welding.
2. Fuel is made of hydrogen gas
3. Vegetable oil is hydrogenated using hydrogen.
4. Ammonia gas, which is used to make fertilisers, is made mostly from hydrogen gas.
12. Define:
(a) Catalytic hydrogenation
(b) Oxidation
(c) Reduction
(d) Redox reaction
Answer:
(a) Catalytic hydrogenation: This technique turns vegetable oils into solid vanaspati ghee by passing hydrogen gas through them while a catalyst like Ni, Pt, or Pd is present.
(b) Oxidation: An oxidation reaction is one in which a substance combines with oxygen or undergoes hydrogen removal. For instance, H2S + Cl → 2HCl + S
(c) Reduction: Reduction reactions are those in which oxygen is taken out of a substance or hydrogen is combined with it. Redox processes, in which one component is reduced while the other is oxidised, occur when both reduction and oxidation occur at the same time. For instance,
d) Redox Reaction: Redox reactions are those in which one substance is reduced while the other is oxidized, or when both reduction and oxidation occur at the same time.
13. Multiple Choice Questions:-
(a) Equal volumes of hydrogen and chlorine are exposed to diffused sunlight to prepare
a) Hydrogen chloride
b) Water
c) Sodium hydroxide
d) Hydrochloric acid
Answer: A
(b) The metal which reacts with cold water to produce hydrogen is:
a) magnesium
b) aluminum
c) calcium
d) iron
Answer: C
(c) In metal activity series the more reactive metals are at:
a) top
b) bottom
c) middle
d) none
Answer: A
(d) Hydrogen is responsible for producing
a) heat and light
b) hydrogenated oil
c) Fertilizers
d) all of the above
Answer: D
(e) Hydrogen is
a) combustible
b) non-combustible
c) supporter of combustion
d) neither supporter nor combustible
Answer: A
(f) Water gas is a mixture of
a) Carbon monoxide and oxygen
b) Carbon monoxide and hydrogen
c) Hydrogen and oxygen
d) Hydrogen and nitrogen
Answer: B
