Which one of the following statements regarding gold is not correct?

Which one of the following statements regarding gold is not correct?

24 karat gold is very soft.
22 karat gold is generally used to make ornaments.
22 karat gold contains 22 parts of pure gold and 2 parts of iron to make it hard.
18 karat gold comprises of 75% gold mixed with 25% of copper or silver to make it hard.
This question was previously asked in
UPSC Geoscientist – 2022
The correct answer is that statement C is not correct.
Karat is a measure of gold purity. Pure gold (24 karat) is soft. Gold for jewelry is typically alloyed with other metals like copper, silver, or zinc to increase its hardness and durability.
Statement A is correct: 24 karat gold is pure and very soft. Statement B is correct: 22 karat gold (approx 91.67% pure) is commonly used for making ornaments. Statement D is correct: 18 karat gold is 18/24 = 75% gold, mixed with 25% other metals like copper or silver. Statement C is incorrect because while 22 karat gold contains 22 parts gold and 2 parts alloy, the alloy metals are typically copper, silver, or zinc, not predominantly iron. Iron is not a common alloying metal for standard gold jewelry due to issues like rusting and brittleness.