Study of Compounds – Nitric Acid Quiz - ICSE Class 10 Chemistry
Free practice quiz: Study of Compounds – Nitric Acid (ICSE Class 10 Chemistry). 57 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Nitric acid reacts with copper metal to produce copper(II) nitrate, nitrogen monoxide, and water. What is the balanced chemical equation for this reaction?
- Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O
- 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O
- Cu + 2HNO₃ → Cu(NO₃)₂ + H₂
- Cu + HNO₃ → CuO + NO₂ + H₂O
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Answer: B. 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O
This question tests the ability to balance redox reactions involving nitric acid. Copper is oxidized, and nitrogen in nitrate is reduced. The common products with dilute nitric acid are copper(II) nitrate, nitrogen monoxide (NO), and water. Balancing the half-equations for oxidation and reduction and combining them yields the correct balanced equation.
The brown ring formed in the nitrate test is a complex of iron with nitric oxide. The formula of this complex is typically represented as:
- [Fe(NO)(H₂O)₅]²⁺
- [Fe(NO₂)(H₂O)₅]²⁺
- [Fe(NO)₂(H₂O)₄]⁺
- [Fe(NO)₃(H₂O)₃]³⁺
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Answer: A. [Fe(NO)(H₂O)₅]²⁺
In the brown ring test, nitrate ions are reduced to nitric oxide (NO) by ferrous sulphate. This NO then forms a coordination complex with excess Fe²⁺ ions present in the solution. The complex formed is nitrosyl ferrous ion or nitrosoiron(II) ion, with the formula [Fe(NO)(H₂O)₅]²⁺, which is brown in color and responsible for the characteristic ring.
The chemical formula of nitric acid is HNO₃. What is the oxidation state of nitrogen in this compound?
- +1
- +3
- +5
- +7
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Answer: C. +5
To determine the oxidation state of nitrogen in HNO₃, we assign standard oxidation states to hydrogen (+1) and oxygen (-2). Let the oxidation state of nitrogen be 'x'. The sum of oxidation states in a neutral molecule is zero: (+1) + x + 3(-2) = 0. Solving for x: 1 + x - 6 = 0, which gives x = +5. Thus, the oxidation state of nitrogen in nitric acid is +5.
Which gas is produced when a very active metal like Magnesium reacts with extremely dilute nitric acid?
- Nitrous oxide (N₂O)
- Nitric oxide (NO)
- Nitrogen gas (N₂)
- Ammonia (NH₃)
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Answer: D. Ammonia (NH₃)
When highly reactive metals like magnesium react with extremely dilute nitric acid, the reduction of nitric acid can proceed to the lowest possible oxidation state of nitrogen, which is -3 in ammonia (NH₃). The reaction is complex and often involves the formation of ammonium nitrate, which then reacts further or dissociates. A simplified representation might be: 8Mg + 10HNO₃(extremely dilute) → 8Mg(NO₃)₂ + NH₄NO₃ + 3H₂O, or even 8Mg + 10HNO₃ → 8Mg(NO₃)₂ + NH₃ + H₂O + N₂O (this is a simplified representation and often the product distribution is complex). However, the formation of ammonia or ammonium ions is indicative of the extreme reduction of nitric acid. Considering the options, and the extreme conditions, ammonia is the most likely answer representing the lowest reduction product. Let me verify this. Yes, with extremely dilute nitric acid and active metals, ammonium salts or ammonia can be formed. This is a higher complexity question testing nuanced reaction products.
The reaction of nitrogen dioxide with water forms nitric acid and nitric oxide. If 3 moles of NO₂ react, how many moles of HNO₃ are formed according to the equation 3NO₂ + H₂O → 2HNO₃ + NO?
- 1 mole
- 2 moles
- 3 moles
- 1.5 moles
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Answer: B. 2 moles
The balanced chemical equation is 3NO₂(g) + H₂O(l) → 2HNO₃(aq) + NO(g). The stoichiometry of the reaction shows that 3 moles of nitrogen dioxide (NO₂) produce 2 moles of nitric acid (HNO₃). Therefore, if 3 moles of NO₂ react, 2 moles of HNO₃ are formed.