Question

A greenish yellow gas of halogen family turns moist blue litmus paper red.
A. True
B. False

Answer 1

Hint: Group VII A elements are called halogens. When group VIIA elements react with metals they form salts. That is why group VII A elements are called halogens. Halogen means salt, former derived from Greek word halo means salt, gen means former.

Complete step by step answer:
- All halogen elements are diatomic in nature and exist in dimer form.
- There are five elements in group VII A.
- They are Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At).
- At room temperature Iodine and Astatine are solid in state, Bromine is liquid in state, Fluorine and Chlorine exist as gases.
- Chlorine is a green yellow color gas and bromine is a reddish brown in color.
- Moist blue litmus paper means, blue litmus paper contains some amount of water.
- When chlorine reacts with moist blue litmus paper we can observe the following reaction.
\[\underset{Chlorine}{\mathop{C{{l}_{2}}}}\,+\underset{Water}{\mathop{{{H}_{2}}O}}\,\xrightarrow{{}}\underset{Hydrochloric\text{ }acid}{\mathop{HCl}}\,+\underset{Hypochlorous\text{ }acid}{\mathop{HOCl}}\,\]
- Whenever chlorine reacts with water forms hydrochloric acid and hypochlorous acid as the products.
- The products formed in the above reaction are acidic in nature. So, acids react with blue litmus paper and convert to red.
- Therefore, the greenish yellow color gas is Chlorine.

- So, the given statement is True, the correct option is A.


Note: Acids reacts with blue litmus paper and turns litmus paper to red. When bases react with the red litmus papers it turns them blue. Chlorine gas won’t turn normal blue litmus paper to red. Chlorine will turn moist blue litmus paper to red.