Aqueous zinc chloride (ZnCl2) reacts with aqueous sodium hydroxide (NaOH) to produce zinc hydroxide ( Zn(OH)2 ) and sodium chloride (NaCl). Zinc hydroxide is a white colour precipitate and it is also an amphoteric hydroxide. Therefore, zinc hydroxide is dissolved when excess NaOH is added to the precipitate.
Đang xem: Zncl2 + 2 naoh → zn(oh)2 + 2 nacl
When both solutions are mixed, a white colour precipitate, zinc hydroxide ( Zn(OH)2 ) is formed. In aqueous phase, there are sodium ions, chloride ions, little bit of Zn2+ ions and OH- ions.
From the balanced equation, we can say, 1 mol of zinc chloride reacts with 2 mol of sodium hydroxide and produce 1 mol of zinc hydroxide and 2 mol of sodium chloride.
This equation can be balanced easily from following steps.
ZnCl2 + NaOH = Zn(OH)2 + NaCl
There are two chlorine atoms in the left side. Therefore, to make two chlorine atoms in the right side, make two NaCl as below. ZnCl2 + NaOH = Zn(OH)2 + 2NaCl Now, there are two sodium atoms in the right side. To make two sodium in the left side, make two NaOH. ZnCl2 + 2NaOH = Zn(OH)2 + 2NaCl
Remember that zinc is an amphoteric element and zinc hydroxide is an amphoteric hydroxide.
When aqueous NaOH is added to ZnCl2 solution drop by drop, at one time, Zn(OH)2 precipitate is formed. If you add more aqueous NaOH to the solution which contains the precipitate, precipitate is dissolved and give a colourless solution due to formation of sodium zincate (Na2ZnO2). Sodium zincate is a colourless aqueous solution.
Sometime above equation is written as below.
If you slowly add HCl acid to the
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Due to presence of excess NaOH, reaction will end up with soluble sodium zincate.
Questions asked by students
Ask your question and find the answer free.
How do I decide whether a precipitate is formed or not when NaCl and ZnCl2 solutions are mixed with each other?
Option 1: If you know the concentratins of each solution, you can do a calculation to check Ksp value related to the Zn(OH)2.
In the final solution, if
You can do the experiment by starting from ZnO. Find dilute HCl bottle. Remember that it is good to use solid ZnO to prevent any impurities. Measure the weight ZnO and put it in a beaker. Then slowly add dilute HCl solution until all ZnO is dissolved. When all ZnO is dissolveed, ZnCl2 solution is given as the following reaction.
ZnO + 2HCl → ZnCl2 + H2O
Now, you can continue the rest of the experiment with by adding NaOH to ZnCl2 solution.
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