52.
Which of the following molecules has a bond order of 2.5?

53.
An element of atomic no. 29 belongs to

54.
Which metal is the heaviest in periodic table among the following ?

55.
Ruby and sapphire are oxides of

56.
The chemical name of quartz is

57.
What is the most common salt in sea water ?

58.
Fertiliser having high nitrogen content is :

59.
Which one of the following is found in kidney stones?

60.
Which one of the following is not present in cement ?