Copper chloride (CuCl2) and sodium hydroxide (NaOH) react with each other and gives blue colour copper hydroxide (Ni(OH)2) precipitate and sodium chloride (NaCl) as the precipitate. Copper chloride is a blue colour solution and sodium chloride is a colourless aqueous solution. However, the precipitate, copper hydroxide is not soluble in excess NaOH.
CuCl2(aq) + NaOH(aq) = Cu(OH)2(s) + NaCl(aq)
Copper chloride is soluble in water and dissociates to Cu2+ and Cl- ions. As well as, NaCl readily dissociates to Na+ and OH- ions in water.
Aqueous copper chloride is a blue colour solution and aqueous sodium hydroxide is a colourless solution. When they react with each other, blue colour precipitate, copper hydroxide and colourless sodium chloride solution is given as products.
Adding NaOH crystals to CuCl2 solution
You can see the exact results as mixing aqueous NaOH and aqueous CuCl2 when NaOH crystals are added to aqueous CuCl2.
CuCl2(aq) + NaOH(s) = Cu(OH)2(s) + NaCl(aq)
Balanced equation of copper chloride and sodium hydroxide reaction
CuCl2(aq) + 2NaOH(aq) = Cu(OH)2(s) + 2NaCl(aq)
1 mol of CuCl2 reacts with 2 mol of NaOH and produce 1 mol of Cu(OH)2 and 2 mol of NaCl. Except Cu(OH)2, all other compounds exist as aqueous state in the equation. Cu(OH)2 exists in solid state. Remember that, to write physical states of compounds when you write the balanced equation.
Observations during the CuCl2 + NaOH reaction
When you are slowly adding one chemical to other chemical drop by drop, at one time, you will see a blue colour precipitate is formed in the solution. If you suddenly add one chemical to another, blue precipitate is also formed immediately.
In the presence of excess NaOH, what will happen to the blue colour Cu(OH)2 precipitate?
Copper hydroxide is not soluble in excess sodium hydroxide because copper hydroxide is not a amphoteric hydroxide. Therefore, copper hydroxide precipitate will remain as the blue precipitate when NaOH is added more and more.
Questions asked by students
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There are no other blue colour ydroxide precipitates of 3d metal cations.
What will happen to pH value of NaOH solution when solid CuCl2 is added?
NaOH is a strong base and usually has a high pH value. In CuCl2 solution, there are only Cu2+ and Cl- ions in water, they do not cause for hydrolysis reaction. Therefore, aqueous CuCl2 solution will show a pH value close to seven.
When CuCl2 is added, OH- ions combines with Cu2+ ions and get precipitated. Therefore, OH- concentration of the aqueous solution is reduced. Therefore, pH value is reduced in the solution.
Which cations can be identified by aqueous NaOH from Cu2+ ?
Fe2+, Fe3+, Mn2+, Co2+, Zn2+, Al3+ alkali metals, alkali earth metals and more cations can be identified from Cu2+ from NaOH considering colour changes, giving precipitating and dissolving hydroxide precipitates in excess NaOH.