Class 9 Study of the First Element: Hydrogen Mock Test (ICSE)

Topics in Study of the First Element: Hydrogen

• Position of hydrogen in the periodic table
• Preparation of hydrogen in the laboratory and industry
• Properties of hydrogen
• Oxidation and reduction
• Uses of hydrogen

Study of the First Element: Hydrogen practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following properties highlights a major difference between hydrogen and alkali metals, explaining why hydrogen occupies a unique position in the Modern Periodic Table?

   1. (a)It is a non-metal existing as a gas under normal conditions, whereas alkali metals are solids.
   2. (b)It has one valence electron in its outermost shell.
   3. (c)It shows a valency of one in its binary compounds.
   4. (d)It forms unipositive ions during chemical reactions.
   Show answer and step marks

   1. Correct option: (a) It is a non-metal existing as a gas under normal conditions, whereas alkali metals are solids.+1

   Answer: (a)
2. Q2Multiple choice·1 mark
   Which statement correctly distinguishes the laboratory preparation of hydrogen from its industrial preparation?

   1. (a)In the laboratory, hydrogen is obtained by electrolysis of brine, while industrially it is made by reacting zinc with dilute acid
   2. (b)In the laboratory, hydrogen is obtained by heating ammonium chloride, while industrially it is made by heating limestone
   3. (c)In the laboratory, hydrogen is obtained by reacting zinc with dilute acid, while industrially it is made by passing steam over red hot coke
   4. (d)In the laboratory, hydrogen is obtained by reacting copper with concentrated nitric acid, while industrially it is made by heating coal in air
   Show answer and step marks

   1. Correct option: (c) In the laboratory, hydrogen is obtained by reacting zinc with dilute acid, while industrially it is made by passing steam over red hot coke+1

   Answer: (c)
3. Q3Short answer·2 marks
   During a visit to a science museum, Ravi watches a demonstration with two identical thin rubber balloons. One is filled with air and the other with hydrogen gas from a cylinder. When both are released together in the hall, the hydrogen-filled balloon floats up towards the ceiling while the air-filled balloon stays near the floor. The guide then warns visitors that a spark near the gas cylinder could be dangerous. (a) Explain why the hydrogen-filled balloon rises while the air-filled balloon does not. [1] (b) Write the balanced chemical equation for the reaction of hydrogen with oxygen that makes the gas dangerous near a spark, with the condition needed for the reaction. [1]
   Show answer and step marks

   1. (a) Hydrogen is much lighter (less dense) than air, so the balloon filled with it is pushed upward by the surrounding air.+1
   2. (b) $2H_2 + O_2 \rightarrow 2H_2O$ (on ignition or heating)+1

   Answer: (a) Hydrogen is less dense than air, so the balloon is pushed up. (b) $2H_2 + O_2 \rightarrow 2H_2O$ (on ignition/heating)
4. Q4Short answer·2 marks
   State any two important industrial uses of hydrogen. Name the specific property of hydrogen on which each use is based.
   Show answer and step marks

   1. First industrial use, any one of: hydrogenation of vegetable oils to make vanaspati ghee; manufacture of ammonia by Haber's process; oxy-hydrogen torch for welding and cutting metals; fuel, e.g. liquid hydrogen as rocket fuel; extraction of metals such as tungsten from their oxides; manufacture of hydrogen chloride or methanol; or any other valid industrial use.+0.5
   2. Property on which the first use is based: for hydrogenation, it adds to (combines with) unsaturated oils in the presence of a nickel catalyst (also credit its reducing property); for ammonia, it combines with nitrogen; for the oxy-hydrogen torch and fuel, it burns giving a large amount of heat (high heat of combustion); for metal extraction, it is a reducing agent; for hydrogen chloride or methanol, it combines with chlorine or carbon monoxide.+0.5
   3. Second industrial use, a different one from the same list.+0.5
   4. Property on which the second use is based, matching that use as listed above.+0.5

   Answer: Any two of: hydrogenation of oils to make vanaspati ghee (adds to unsaturated oils with a nickel catalyst); manufacture of ammonia by Haber's process (combines with nitrogen); oxy-hydrogen torch for welding (high heat of combustion); rocket fuel (burns giving much heat); extraction of metals from oxides (reducing agent).
5. Q5Long answer·4 marks
   Hydrogen is used in several industrial processes and in space technology. Answer each part. (a) Hydrogen is reacted with nitrogen at about 450 °C and 200 atmospheric pressure in the presence of a finely divided iron catalyst. Name the compound formed. [1] (b) Liquid vegetable oil is heated with hydrogen in the presence of finely divided nickel as catalyst to form a solid fat. Name this process. [1] (c) Liquid hydrogen is used as a fuel in rockets. Name the substance that must be carried along with it to support its combustion. [1] (d) Hydrogen is burnt in an excess of chlorine to form a gas that dissolves in water to give hydrochloric acid. Name the gas formed. [1]
   Show answer and step marks

   1. (a) Ammonia, the compound formed by the Haber process: $N_2 + 3H_2 \rightarrow 2NH_3$.+1
   2. (b) Hydrogenation, the addition of hydrogen to unsaturated oils to form saturated fats (Vanaspati ghee).+1
   3. (c) Liquid oxygen, which acts as the oxidiser for the hydrogen fuel.+1
   4. (d) Hydrogen chloride, $HCl$.+1

   Answer: (a) Ammonia ($NH_3$); (b) Hydrogenation; (c) Liquid oxygen; (d) Hydrogen chloride ($HCl$)
6. Q6Long answer·4 marks
   Hydrogen occupies a unique position in the Modern Periodic Table due to its dual resemblance with alkali metals and halogens. (a) State any two points of similarity between hydrogen and alkali metals. [2] (b) State any two points of resemblance between hydrogen and halogens, and explain why it is placed separately in the periodic table. [2]
   Show answer and step marks

   1. (a) First similarity with alkali metals, any one of: both have one electron in the outermost shell (H: 1, Na: 2, 8, 1); both lose that electron to form a positive ion with charge $+1$ ($\text{H}^+$, $\text{Na}^+$); both have valency $1$; both form similar compounds such as oxides, halides and sulphides ($\text{H}_2\text{O}$, $\text{Na}_2\text{O}$; $\text{HCl}$, $\text{NaCl}$; $\text{H}_2\text{S}$, $\text{Na}_2\text{S}$); both act as reducing agents; or any other valid similarity.+1
   2. (a) Second similarity with alkali metals, a different one from the same list.+1
   3. (b) First resemblance with halogens, any one of: both exist as diatomic molecules ($\text{H}_2$, $\text{Cl}_2$); both need one more electron to attain the nearest noble gas configuration (He for H, Ar for Cl); both gain one electron to form a negative ion with charge $-1$ ($\text{H}^-$ in $\text{NaH}$, $\text{Cl}^-$ in $\text{NaCl}$); both have valency $1$; both are non-metals that form covalent compounds with other non-metals ($\text{CH}_4$, $\text{CCl}_4$); or any other valid similarity.+0.5
   4. (b) Second resemblance with halogens, a different one from the same list.+0.5
   5. (b) Reason for separate placement: hydrogen resembles both alkali metals and halogens but also differs from both (it is a non-metal unlike alkali metals, and it is far less reactive and electronegative than halogens), so it cannot be placed fully in either group.+1

   Answer: (a) Any two of: one valence electron; forms $\text{H}^+$ like $\text{Na}^+$; valency $1$; similar oxides, halides and sulphides; reducing agent. (b) Any two of: diatomic molecules ($\text{H}_2$, $\text{Cl}_2$); one electron short of a noble gas configuration; forms $\text{H}^-$ like $\text{Cl}^-$; valency $1$; forms covalent compounds. It is placed separately because it resembles both groups yet differs from both (non-metal, far less electronegative than halogens).

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