IGCSE Chemistry: Specimen Questions with Answers 154 - 156 of 240

The positions of four elements are shown on the outline of the Periodic Table.

Which element forms a colored oxide?

Explanation

Correct option is D because D represent element Chromium and the main oxide of chromium is .

And the color of this oxide is dark green while other option some of them do not form oxide and some form oxide but forms colorless oxide.

Answer

TRUE

Explanation

• Baking soda is used in fire extinguisher. Baking soda is chemically known as sodium bicarbonate.
• When heated to a high temperature, the chemical properties of this salt make it produce lots of carbon dioxide and remove oxygen. This then totally reduces the amount of oxygen in the surrounding atmosphere and puts the fire out.
• This reaction also produces a small quantity of water and sodium carbonate as by-products.

Which of the following is an example of alkali metal?

Answer

Explanation

Elements having one valence electron are kept in group in the periodic table. Examples of group elements include lithium, sodium, potassium etc. Group elements are also known as alkali metals. This is because on reaction with water, these elements form their corresponding water soluble hydroxides which are called as alkali.