Question

A greenish-yellow gas burns in a rotten-egg smelling gas giving an acidic gas and a yellow coloured non-metal. Write the balanced chemical equation for the reaction.

Answer 1

Hint: Non-metals are the elements that are in the p-block of the periodic table. p-block elements have p orbital as their valence orbital. The rotten egg smelling gas has the non-metal atom which is yellow in colour.

Complete step by step solution:
We are given a reaction in which some of the characteristics of the reactants and the products are given to us. Let’s write it in the form of reaction in order to understand it better.
\[{\text{Greenish yellow gas + Gas with Rotten egg smell}} \to {\text{Acidic gas + Yellow Non - metal}}\]
-The easiest characteristic to guess is the yellow non-metal. Most probably it should be sulphur. Sulphur is solid and as it is a p-block element, it can be characterized as a non-metal.
-So, this sulphur should be there in either greenish-yellow gas or in the gas with rotten egg smell. We would have come across a gas containing sulphur atom and has a rotten egg smell. This gas is hydrogen sulphide (${H_2}S$).
-So, if we accept that the gas with rotten egg smell is hydrogen sulphide, then the two hydrogen atoms should be there in the acidic gas.
-Now, think about a greenish-yellow coloured gas which can give an acidic gas when reacted with hydrogen sulphide. The greenish-yellow coloured gas should be chlorine gas. So, all the chosen gases match the characteristics given in the compound. So, we can write the balanced reaction as
\[C{l_{2(g)}} + {H_2}{S_{(g)}} \to 2HC{l_{(g)}} + {S_{(s)}}\]

Note: Note that as HCl has an ionic bond, it can lose a proton and behave as an acid. Actually, hydrochloric acid is in gaseous form when formed. The HCl we use in our lab is its solution in water.