Question

Copper chloride and sodium hydroxide react and one of the products is precipitation.

Answer 1

Hint: We must need to know that transition elements are d block elements and they are colored in nature. Copper chloride is a coordination complex. Copper is a $3d$ block element having atomic number $29$ . On the other hand, sodium hydroxide is a strong base.

Complete answer:
We must remember that transition metals form colored compounds with other elements. Many of these are soluble in water, forming colored solutions. If sodium hydroxide solution is then added, a transition metal hydroxide is formed. Transition metal hydroxides are insoluble so they form solid precipitates. These precipitates often appear as small particles suspended in a solution. Here are the equations for copper sulfate solution reacting with sodium hydroxide solution:
Copper(II) chloride + sodium hydroxide → copper(II) hydroxide + sodium chloride
\[CuC{l_2}\left( {aq} \right) + 2NaOH\left( {aq} \right) \to Cu{\left( {OH} \right)_2}\left( s \right) + 2NaCl\left( {aq} \right)\]
(blue solution + colorless solution → blue precipitate + colorless solution)
Copper chloride is soluble in water and dissociates to $C{u^{2 + }}$ and $C{l^ - }$ ions. As well as, $NaOH$ readily dissociates to Na+ and OH- ions in water. Aqueous copper chloride is a blue color solution and aqueous sodium hydroxide is a colorless solution. When they react with each other, blue color precipitate, copper hydroxide and colorless sodium chloride solution is given as products.

Note:
We must know that the reaction between copper chloride and sodium hydroxide can be known as double displacement reaction since ions for both reactants are changing with each other. We must look at a completely balanced equation as in the above chemical reaction two moles of sodium hydroxide and two moles of sodium chloride balanced this equation.