B. Precipitates and their Solubility in Strong Acids Carbonate Precipitation of
ID: 503759 • Letter: B
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B. Precipitates and their Solubility in Strong Acids Carbonate Precipitation of Carbonates. We know that sodium carbonate is a strong electrolyte, so it ionizes completely. (R12) Na2CO3(aq) 2Na (aq) co32 (aq) Cu (aq) will form a carbonate precipitate, Cuco3 (s) with the [Co32] under appropriate conditions. Now try this with each of the seven metal cations: K+, Ba2+, 2+ 2+ Co2+, 2+ Fe3+ Mn Ni 1. Write out the correspoding solubility equilibrium equations that would give rise to a carbonate precipitate. Be to use the appropriate arrows v depending on the careful compound's solubility. Using the Ksp values provided in Table 2, predict whether it would form using 0.5 MNa2CO3 and 0.10 metal nitrate solution 2. Test your preditions in the lab. Do your results match your predictions? Clearly describe your observations. he purpose of this exercise, it is OK to use the iron(I) carbonate solubility equilibrium for your prediction calculation, but technically, that's not the precipitate but you formed. Looking at Table 2, you can see that an iron(II) carbonate precipitate is possible, compare its Ksp to that of iron (IID hydroxide. The hydroxide precipitate is highly favored Remember that the carbonate ion can act as a weak base in an aqueous solution (R13) Co (aa) H20 (l) HCO3 (aq) OH (aq) Once there is a source of hydroxide ions, the iron will first for the hydroxide precipitate on Notice, too, that the Ksp or n(IID hydroxide is much smaller than that of any other cation iron the list 135Explanation / Answer
1. Alkali metal ions like Na+ and K+ form completely soluble carbonates and hence the concept of Ksp doesn’t work here. The reaction of carbonate (CO32-) with K+ is as below:
K2CO3 (aq) <=====> 2 K+ (aq) + CO32- (aq)
Compose a table with the rest of the cations and find out the concentrations.
Equilibrium Equation
Ksp
Expression for reaction quotient Q
Value of reaction quotient Q
Whether a precipitate will form or not
BaCO3 (s) <=====> Ba2+ (aq) + CO32- (aq)
2.6*10-9
Q = [Ba2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
ZnCO3 (s) <=====> Zn2+ (aq) + CO32- (aq)
1.5*10-10
Q = [Zn2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
MnCO3 (s) <====> Mn2+ (aq) + CO32- (aq)
2.2*10-11
Q = [Mn2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
CoCO3 (s) <=====> Co2+ (aq) + CO32- (aq)
1.6*10-13
Q = [Co2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
NiCO3 (s) <=====> Ni2+ (aq) + CO32- (aq)
1.4*10-7
Q = [Ni2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
Fe2CO3 (s) <=====> 2 Fe3+ (aq) + 3 CO32- (aq)
3.1*10-11
Q = [Fe3+]2[CO32-]3
Q = (0.10)3(0.5)2 = 2.5*10-4
Yes, Q is much higher than Ksp
Equilibrium Equation
Ksp
Expression for reaction quotient Q
Value of reaction quotient Q
Whether a precipitate will form or not
BaCO3 (s) <=====> Ba2+ (aq) + CO32- (aq)
2.6*10-9
Q = [Ba2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
ZnCO3 (s) <=====> Zn2+ (aq) + CO32- (aq)
1.5*10-10
Q = [Zn2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
MnCO3 (s) <====> Mn2+ (aq) + CO32- (aq)
2.2*10-11
Q = [Mn2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
CoCO3 (s) <=====> Co2+ (aq) + CO32- (aq)
1.6*10-13
Q = [Co2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
NiCO3 (s) <=====> Ni2+ (aq) + CO32- (aq)
1.4*10-7
Q = [Ni2+][CO32-]
Q = (0.10)(0.5) = 0.05
Yes, Q is much higher than Ksp
Fe2CO3 (s) <=====> 2 Fe3+ (aq) + 3 CO32- (aq)
3.1*10-11
Q = [Fe3+]2[CO32-]3
Q = (0.10)3(0.5)2 = 2.5*10-4
Yes, Q is much higher than Ksp
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