Dry hydrogen chloride gas does not effect a dry strip of blue litmus paper but it turns red in the presence of a drop of water ?

Dry hydrogen chloride gas does not effect a dry strip of blue litmus p

1.	Dry hydrogen chloride gas does not effect a dry strip of blue litmus paper but it turns red in the presence of a drop of water ?
Answer» Any acid is said to be an acid if there is a proton acceptor to accept the proton donated by the acid. Since water ACCEPTS a proton to FORM a hydronium ion, the acid is ionized. A DRY strip of litmus and dry HCl in gaseous form do not contain water so HCl does not ionize, but in PRESENCE of a DROP of water, HCl is ionized and releases a proton which turns blue litmus red.