part A A. Effect of lowering the pH on the solubility of an insoluble salt. 1. O

Question

part A

A. Effect of lowering the pH on the solubility of an insoluble salt.

1. Obtain 5.0 mL each of 1.0 M calcium chloride and 0.25 M sodium oxalate solutions

2. Pour both solutions into a 50 mL beaker (mixing well). What reaction has occurred?

3. Add approximately 10 mL of 6 M nitric acid and stir. What reaction has occurred? What do you observe? Dispose of the solution in the appropriate waste receptacle and thoroughly clean the beaker.

this is all we did for partA

1. Write the equilibrium reaction for the mixture in the beaker in Part A, step 2.

Write the net ionic equation for the reaction (which involves one of the species in the reaction that you’ve just written) that occurs when nitric acid is added to the beaker in Part A.

Examine the two reactions shown above for part A and explain, using Le Châtelier’s principle, why the changes occurred in the beaker after adding nitric acid.

Explanation / Answer

The reaction that occurs when

CaCl2(aq) + Na2C2O4(aq) --> 2NaCL(aq) + CaC2O4(s)

net ionic:

Ca2+(aQ) + C2O4-2(aq) --> CaC2O4(s)

there is precipitation of Calcium Oxalate

Q2

when adding acid:

CaC2O4 + H+ <--> Ca+ + HC2O4-

acid forms

the solid must dissapear since Ca now is in ionic tate

LE chatelier logic:

when we add CaCl2 and Na2C2O4, there is plenty of reactants in order to saturate the solution and form solid, which is shifted toward solid production

when we add:

H+ from storng acid

the shift will go toward H2C2O4 production, so the Ca+2 and C2O4-2 shift favours the ionic tate of Calcium

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