31.

The first metal used by man was
A. iron B. copper
C. gold D. bronze
Answer and Explanation
Answer:B
Explanation: No answer description available for this question.
32.

The most electropositive elements among the following is
A. Na B. Ca
C. K D. Cs
Answer and Explanation
Answer:D
Explanation: No answer description available for this question.
33.

The method that cannot be used for removing permanent hardness of water is
A. adding sodium carbonate B. distillation
C. adding caustic soda D. boiling
Answer and Explanation
Answer:D
Explanation: No answer description available for this question.
34.

The following are the half lives of four active isotopes. Which one of the following is the most dangerous to handle?
A. 3 billion years B. 100 years
C. 0.01 minute D. 13 days
Answer and Explanation
Answer:C
Explanation: No answer description available for this question.
35.

The gas used for artificial ripening of green fruit is
A. ethylene B. ethane
C. carbon dioxide D. acetylene
Answer and Explanation
Answer:A
Explanation: No answer description available for this question.