In 1931, who recognised that an aromatic compound must have an odd number of pairs of electrons, which can mathematically be written as 4n+2 (n = 0,1,2,3 etc.)?

Which of the following substances cannot act as both acid as well as a base?

Read the following questions carefully and answer them. 

The gas used for artificial fruit ripening of green fruit is —

Which of the following is a Lewis base?

In 1845, which German chemist published a method for the synthesis of acetic acid, a natural product containing two carbon atoms?

Which is the most economical method of removing solid matter from water?

Which of the following process is used to do maximum work done on the ideal gas if the gas is compressed to half of its initial volume?

Read the following questions carefully and answer them. 

The polymer used in making plastic crockery is