Question

A piece of zinc metal dropped in are dilutesolution of hydrochloric acid.
(a) which gas is liberated when a metal reacts with acid
(b) how Will you test the presence of this gas
(c) is it lighter or heavier than air
(d) how will you collect the above gas

Answer 1

(a) hydrogen gas is liberated
(b) by taking a burning candle near the mouth of test tube 
(c) it is lighter than air
(d) we will collect the gas by taking a test tube over it