Question

Identify ‘X’ in the reaction: $ 2HCl + CuO \to X + {H_2}O $ .

Answer 1

Hint : the reaction that is taking place here is a double displacement reaction. The compound formed is a blue-green solution. $ CuO $ is a metal oxide so try to find out how a metal oxide will react with an acid to form the compound.

Complete Step By Step Answer:
The reaction here is a double displacement reaction where two compoundsṣ react with each other by exchange of cation and anion ions to form a new compound. This usually takes place with those compounds who can be dissolved in water easily. A general equation showing double displacement reaction is: $ AB + CD \to AD + CB $
Here when $ 2HCl $ is reacting with the metal oxide $ CuO $ the product that is formed is $ CuC{l_2} $ (Copper chloride). This is a blue-green colored compound. $ CuO $ is metal oxide which is basic in nature and $ HCl $ is acidic so when they both react what we get is a salt $ CuC{l_2} $ and water.
 $ CuC{l_2} $ is an ionic compound which gets dissolved in water easily and dissociates to give $ C{u^{2 + }} $ and $ 2C{l^ - } $ ions. So it is completely soluble in water and when it dissolves in water the water turns bluish in color. This $ CuC{l_2} $ is corrosive to aluminum. It is used in various industries for the manufacturing of other chemicals, in printing industries etc. it is very toxic for aquatic organisms, and may result in long-term diseases. On industrial scale $ CuC{l_2} $ is prepared by the chlorination of copper.
Therefore ‘X’ is $ CuC{l_2} $ and the complete reaction is $ 2HCl + CuO \to CuC{l_2} + {H_2}O $

Note :
When any metal oxide reacts with an acid, being base metal oxide will neutralize the acid and the product formed is salt and water. In our case the salt is $ CuC{l_2} $ . After the reaction has occurred the solution turns into bluish-green. The anhydrous form of $ CuC{l_2} $ is yellowish brown but slowly absorbs moisture to form a blue-green dihydrate.