Observations on addition of a drop of 6 M NaOH to Zn(NO_3)_2 solution: Effect on
ID: 488954 • Letter: O
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Observations on addition of a drop of 6 M NaOH to Zn(NO_3)_2 solution: Effect on solubility of Zn(OH)_2: a. Of added HCI solution b. Of added NaOH solution c. Of added NH_3 solution Observations on addition of one drop of 6 M NaOH to Mg(NO_3)_2 solution: Effect on solubility of Mg(OH)_2: a. Of added HCI solution b. Of added NaOH solution c. Of added NH_3 solution Explain you observations in step 1. (Consider Reaction 8; boss is it affected by addition of OH^- ion?) In Step 2(a), boss does an increase in [H*] affect Reaction 3? (What does that do to Reaction 8?) Explain your observations in Step 2(a). In Step 2(b), how does an increase in [OH^-] affect Reaction 9? What does that do to Reaction 8? Explain your observations in Step 2(b). In Step 2(c). how does an increase in [NH_3] affect Reaction 10? What does that do to Reaction 8? Explain your observations in Step 2(c). In Step 3, you probably found that Mg(OH)_2 was similar in some ways in its behavior to that of Zn(OH)_2, but different in others. a. How was it similar? Explain that similarity. (In particular, why would any insoluble hydroxide tend to dissolve in acidic solution?) b. How was it different? Explain that difference. (In particular, does Mg^2+ appear to form complex ions with OH^- and NH_3? What would we observe if it did? If it did not?)Explanation / Answer
LeChatellier's principle : When an equilibrium state is disturbed, the reaction goes in that direction that minimizes the effect and returns back to equilibrium state.
1. Zn(NO3)2 forms precipitate with NaOH.
2. Zn(OH)2 <==> Zn2+ + 2OH-
a. when HCl is added, OH- reacts with added H+ and thus more Zn(OH)2 dissolved
b. When NaOH is added, more Zn(OH)2 formed
c. When NH3 is added, no effect was seen
3. Mg(OH)2 <==> Mg2+ + 2OH-
a. when HCl is added, OH- reacts with added H+ and thus more Mg(OH)2 dissolved
b. When NaOH is added, more Mg(OH)2 formed
c. When NH3 is added, no effect was seen
Both hydroxie solubility increased by adding HCl and reduced by adding NaOH.
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