Consider the following reaction : 2HgO → 2Hg + O₂ The respective state of HgO, Hg and O₂ in the above reaction is
- A.Liquid, solid, gas
- B.Solid, solid, gas
- C.Liquid, solid, liquid
- D.Solid, liquid, gas
Correct answer
Explanation
The correct answer is D, Solid, liquid, gas. Mercury(II) oxide is a red-orange solid, mercury is a liquid metal at room temperature, and oxygen is a gas.
This is a thermal decomposition reaction: when mercuric oxide is heated, it breaks down into mercury and oxygen, written with states as 2HgO(s) → 2Hg(l) + O₂(g). Mercury is the only metal that is liquid at ordinary temperatures, with a melting point of about −39 °C. The reaction has a place in the history of chemistry: Joseph Priestley obtained oxygen in 1774 by heating mercuric oxide with sunlight focused through a lens, and Antoine Lavoisier used the same reaction to explain combustion.
A is wrong: mercuric oxide is a solid, not a liquid, and mercury is not a solid.
B is wrong: mercury is a liquid at room temperature, not a solid.
C is wrong: oxygen is a gas, and mercuric oxide is not a liquid.
Exam tip: mercury is the only liquid metal and bromine the only liquid non-metal at room temperature.
Practice Questions
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- A.GH
- B.TSH
- C.Insulin
- D.Cortisol
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- A.sinoatrial node
- B.QRS wave
- C.T wave
- D.hepatic portal system
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Read the full explanation →The equivalent weight of Ba(OH)2 is (given, atomic weight of Ba is 137.3)
- A.85.7
- B.137.3
- C.154.3
- D.171.3
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- A.1 and 2
- B.1 and 3
- C.2 and 4
- D.1 and 4
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- A.Protein only
- B.Lipid
- C.Carbohydrate only
- D.Protein and Carbohydrate
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