CAPF AC 2022 Q37: Science & Technology – Chemistry
White gold is an alloy of
- (a) gold, nickel and palladium
- (b) gold, cobalt and palladium
- (c) gold, titanium and platinum
- (d) gold, magnesium and palladium
Answer: (a) gold, nickel and palladium
Explanation
White gold
How to think: pure gold is yellow and soft.
To make it white and hard, it is mixed with white metals.
The usual ones are nickel and palladium (sometimes silver or zinc as well).
| Alloy | Made of |
|---|---|
| White gold | Gold + nickel + palladium |
| Rose gold | Gold + copper |
| 22 carat gold | 22 parts gold + 2 parts copper or silver |
| Electrum | Gold + silver, found naturally |
Extra fact: white gold jewellery is often coated with rhodium for a bright finish.
Pure gold is 24 carat.
Answer: (a) gold, nickel and palladium.
Why each option is right or wrong
- (a) CORRECT. White gold is gold alloyed with white metals such as nickel and palladium.
- (b) Incorrect. Cobalt is not the standard metal used in white gold.
- (c) Incorrect. Titanium and platinum are not the usual mix for white gold.
- (d) Incorrect. Magnesium is a light reactive metal, not used in gold jewellery.
Key point
White gold: gold + nickel and/or palladium (often rhodium plated). Rose gold: gold + copper. Pure gold: 24 carat; 22 carat is 91.6% gold. Aqua regia dissolves gold.
Remember
White gold = gold + nickel + palladium.
Common mistakes
- Thinking white gold is another name for platinum.
- Guessing cobalt or titanium because they are modern-sounding metals.
- Believing white gold is a pure metal and not an alloy.
Exam tip
Educated guess: three options contain palladium, so it is surely part of the answer. Of the partners offered, nickel is the common silvery-white metal used in coins and alloys.
Sources
- NCERT Class X Science — Metals and Non-metals (alloys; purity of gold in carats)
- World Gold Council — About gold jewellery: white gold and carats