41.
The first metal used by man was

42.
The hydronium ion is

44.
The method that cannot be used for removing permanent hardness of water is

45.
The following are the half lives of four active isotopes. Which one of the following is the most dangerous to handle?

46.
The gas used for artificial ripening of green fruit is

47.
Zone refining is used for the purification of

48.
The main chemical constituent of the oil of cardamom which is responsible for flavour of this oil is

49.
The molecule which has the highest percentage of ionic character among the following is

50.
The high reactivity of fluorine is due to