Extra class

What is the purity of 18 carat gold?

• 50%

• 75%

• 80%

• 90%

What percentage of pure gold is in a 14-carat gold?

• 50%

• 60%

• 80%

• 70%

What is the color of pure diamonds?

• Yellow

• Blue

• Green

• Colorless

How to obtain sodium chloride from seawater?

• Boiling

• Freezing

• Evaporating

• Condensing

Silver is usually marked with the number of parts per thousand that are silver. The silver ring has the mark 925 on it. What is the percentage of purity of Silver in the ring?

• 90%

• 92.5%

• 95%

• 925%

Diamonds are made of the element ....

• Gold

• Silver

• Carbon

• Boron

Yellow diamond is a diamond which has some ............ element on it.

• Boron

• Nitrogen

• Nickel

• Silver

Silver is usually marked with the number of parts per thousand that are silver. So, what is the purity of silver marked 825?

• 100%
• 80%
• 12.5%

• 82.5%

The mass of the impure product is 15 grams, and the mass of the pure product is 12 grams. Calculate the percentage purity.

• 80%
• 90%
• 100%
• 120%

What other minerals that can change white diamond to blue diamond?

• Nitrogen

• Helium

• Hydrogen

• Boron

Answer explanation

0.05% of trace element that helps to form natural diamond colour.