Class 10 Study of Compounds: Nitric Acid Mock Test (ICSE)

Topics in Study of Compounds: Nitric Acid

• Laboratory preparation of nitric acid
• Ostwald's process
• Properties of nitric acid
• Nitric acid as an oxidising agent

Study of Compounds: Nitric Acid practice questions with answers

1. Q1Multiple choice·1 mark
   Concentrated nitric acid reacts with sulphur to produce sulphuric acid and:

   1. (a)Nitrous acid and oxygen
   2. (b)Nitric oxide and water
   3. (c)Nitrogen pentoxide and hydrogen
   4. (d)Nitrogen dioxide and water
   Show answer and step marks

   1. Correct option: (d)+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   When concentrated nitric acid is exposed to sunlight, it turns yellow due to the dissolution of:

   1. (a)Nitric oxide gas
   2. (b)Nitrogen pentoxide
   3. (c)Oxygen gas
   4. (d)Nitrogen dioxide gas
   Show answer and step marks

   1. Correct option: (d)+1

   Answer: (d)
3. Q3Multiple choice·1 mark
   In the laboratory preparation of nitric acid, concentrated sulphuric acid is preferred over concentrated hydrochloric acid because:

   1. (a)Sulphuric acid is a monobasic acid.
   2. (b)Hydrochloric acid reacts to form chlorine gas instead of nitric acid.
   3. (c)Sulphuric acid is cheaper than hydrochloric acid.
   4. (d)Concentrated hydrochloric acid is volatile and its vapors would contaminate the nitric acid.
   Show answer and step marks

   1. Correct option: (d)+1

   Answer: (d)
4. Q4Short answer·2 marks
   (i) Name the reactants used in the laboratory preparation of nitric acid. (ii) Why is an all-glass apparatus used instead of standard glass apparatus with cork stoppers?
   Show answer and step marks

   1. (i) First reactant: potassium nitrate ($\text{KNO}_3$) (or sodium nitrate, $\text{NaNO}_3$).+0.5
   2. (i) Second reactant: concentrated sulphuric acid ($\text{H}_2\text{SO}_4$).+0.5
   3. (ii) Nitric acid vapour is highly corrosive and attacks cork and rubber stoppers, so an all-glass apparatus is used.+1

   Answer: (i) Potassium nitrate (or sodium nitrate) and concentrated sulphuric acid. (ii) Nitric acid vapour corrodes cork and rubber, so all-glass apparatus is used.
5. Q5Long answer·4 marks
   Answer the following questions based on the industrial manufacture of nitric acid by Ostwald's process: (a) Write the balanced chemical equation for the catalytic oxidation of ammonia. Mention the specific catalyst and the optimum temperature required for this reaction. (b) What happens when the nitric oxide produced in the first step is cooled and reacted with air? Write the balanced chemical equation and state the physical observation regarding the change in colour.
   Show answer and step marks

   1. (a) Balanced equation: $4\text{NH}_3 + 5\text{O}_2 \xrightarrow[800^\circ\text{C}]{\text{Pt}} 4\text{NO} + 6\text{H}_2\text{O} + \text{Heat}$+1
   2. (a) Catalyst: platinum (platinum gauze, $\text{Pt}$).+0.5
   3. (a) Optimum temperature: about $800^\circ\text{C}$.+0.5
   4. (b) Balanced equation for the oxidation of nitric oxide: $2\text{NO} + \text{O}_2 \rightarrow 2\text{NO}_2$+1
   5. (b) Observation: colourless nitric oxide ($\text{NO}$) changes to reddish-brown nitrogen dioxide ($\text{NO}_2$).+1

   Answer: (a) $4\text{NH}_3 + 5\text{O}_2 \xrightarrow{\text{Pt}} 4\text{NO} + 6\text{H}_2\text{O}$; catalyst: platinum; temperature: about $800^\circ\text{C}$. (b) NO combines with oxygen of the air to form nitrogen dioxide: $2\text{NO} + \text{O}_2 \rightarrow 2\text{NO}_2$; the colourless gas turns reddish brown.
6. Q6Long answer·4 marks
   Answer the following questions regarding Ostwald's process for the manufacture of nitric acid: (a) Write the balanced chemical equation for the catalytic oxidation of ammonia, specifying the catalyst and temperature required. [2] (b) State the balanced chemical equation for the oxidation of nitric oxide to nitrogen dioxide. [1] (c) Write the balanced chemical equation for the final step where nitrogen dioxide is converted to nitric acid. [1]
   Show answer and step marks

   1. (a) $4NH_{3(g)} + 5O_{2(g)} \xrightarrow[800^\circ\text{C}]{Pt} 4NO_{(g)} + 6H_2O_{(g)}$+1
   2. (a) Catalyst: platinum ($\text{Pt}$ gauze).+0.5
   3. (a) Temperature: about $800^\circ\text{C}$ ($700^\circ\text{C}$ to $800^\circ\text{C}$ also accepted).+0.5
   4. (b) $2NO_{(g)} + O_{2(g)} \rightarrow 2NO_{2(g)}$+1
   5. (c) $4NO_{2(g)} + 2H_2O_{(l)} + O_{2(g)} \rightarrow 4HNO_{3(aq)}$+1

   Answer: (a) $4NH_3 + 5O_2 \xrightarrow{Pt,\ 800^\circ\text{C}} 4NO + 6H_2O$; catalyst platinum, about $800^\circ\text{C}$. (b) $2NO + O_2 \rightarrow 2NO_2$. (c) $4NO_2 + 2H_2O + O_2 \rightarrow 4HNO_3$.

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