Half-life of a radioactive substance is 5 years. After 10 years, how much of the original amount remains? MCQ with Answer and Explanation

Explanation:
Ozone decomposes to O₂, leaving no residual taste or toxic by-products like trihalomethanes. However, it must be generated on-site and is more expensive.

Explanation:
Arsenic (As) is a metalloid, showing properties of both metals and non-metals. It is in group 15, period 4. Sodium and calcium are metals. Oxygen is a non-metal. Metalloids: B, Si, Ge, As, Sb, Te. They are semiconductors and form amphoteric oxides.

Explanation:
Water (H₂O) is a compound – a pure substance composed of two or more elements chemically combined in a fixed ratio. Oxygen is an element. Air is a mixture of gases. Steel is an alloy (mixture). Compounds can be broken down by chemical methods.