Aqua regia, which dissolves gold, is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio:
- A.1:1
- B.1:3
- C.3:1
- D.2:3
Correct answer
Explanation
The correct answer is C, 3:1. Aqua regia is three parts concentrated hydrochloric acid to one part concentrated nitric acid, and the name means royal water, given because the mixture attacks the noble metals gold and platinum, which neither acid can dissolve on its own. Option B, 1:3, is the same pair of acids in the reverse order and is the commonest wrong answer, so note that the larger share is hydrochloric acid. Options A and D do not correspond to any standard laboratory reagent of this kind. The chemistry is worth one line: nitric acid oxidises the gold and the chloride from hydrochloric acid holds the resulting ions in solution, so each acid does what the other cannot. Aqua regia is used to test the purity of gold and to recover precious metals.
Read the full article: Metals and Non-Metals: Properties, Ores and Alloys
Practice Questions
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- A.Tin
- B.Magnesium
- C.Zinc
- D.Copper
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Read the full explanation →Which of the following is NOT an alloy?
- A.Solder
- B.Silver
- C.Bronze
- D.Brass
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Read the full explanation →Which of the following is the most ductile metal?
- A.Gold
- B.Copper
- C.Silver
- D.Iron
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Read the full explanation →Brass is an alloy of:
- A.copper and tin
- B.copper and nickel
- C.copper and iron
- D.copper and zinc
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Read the full explanation →Which metal is in the liquid state at room temperature?
- A.Sodium
- B.Mercury
- C.Lead
- D.Tungsten
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Mercury is the only metal that is liquid at ordinary room temperature, which is why it was long used in thermometers and barometers; it is also the metal that forms amalgams, alloys in which mercury is one component.
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