Given the reaction at equilibrium:
BaSO4(s) ↔ Ba2+(aq) + SO42–(aq)
BaSO4<--> Ba2+. + SO42-
The concentration of SO42– ions can be decreased by the addition of
A) BaSO4(s)
B) BaCl2(s)
C) Na2SO4(s)
D) NaNO3(s)
B
Adding BaCl2 will increase the (Ba^2+) and that will shift the solubility of
BaSO4(s) ==> Ba^2+ + [SO4]^2- to the left so more BaSO4 will ppt. That will decrease the [SO4]^2-
Well, this is a sulfate situation! If we want to decrease the concentration of SO42– ions, we need to shift the equilibrium to the left. And one way to do that is by adding BaSO4, because, well, it's already on the left side of the reaction.
So the answer is A) BaSO4(s). Just throw some more BaSO4 into the mix and watch those SO42– ions disappear! It's like magic, but with chemistry.
To decrease the concentration of SO42– ions, you would need to shift the equilibrium to the left, which means favoring the formation of BaSO4(s). In this case, option A) BaSO4(s) would be the correct answer.
To determine which compound will decrease the concentration of SO42– ions, you need to understand Le Chatelier's principle. According to Le Chatelier's principle, when a system at equilibrium is subjected to a stress (such as a change in concentration, pressure, or temperature), the system will respond by shifting in a way that minimizes the effect of the stress.
In this case, we want to decrease the concentration of SO42– ions. Adding any of the given compounds will increase the concentration of a product (Ba2+ or SO42–) or a reactant (BaSO4) in the equilibrium reaction. According to Le Chatelier's principle, the system will respond by shifting in the direction that reduces this increase.
Let's analyze each option:
A) BaSO4(s): Adding more BaSO4 will increase the concentration of the reactant, which will cause the system to shift towards the product side to reduce the excess reactant. This will actually increase the concentration of SO42– ions instead of decreasing it.
B) BaCl2(s): Adding BaCl2 will introduce a new ion (Ba2+), increasing the concentration of the product. The system will respond by shifting towards the reactant side to reduce this increase. This will decrease the concentration of both Ba2+ and SO42– ions, so it doesn't decrease the concentration of SO42– specifically.
C) Na2SO4(s): Adding Na2SO4 will introduce a new ion (Na+ and SO42–), increasing the concentration of the reactant. The system will shift towards the product side to reduce this increase, resulting in an increase in the concentration of both Ba2+ and SO42– ions. Therefore, it doesn't decrease the concentration of SO42– ions.
D) NaNO3(s): Adding NaNO3 will introduce new ions (Na+ and NO3–), which are not involved in the equilibrium reaction. Therefore, adding NaNO3 will not have any direct effect on the concentrations of Ba2+ or SO42– ions.
Based on Le Chatelier's principle, the compound that will decrease the concentration of SO42– ions is option D) NaNO3(s). Although it doesn't directly affect the equilibrium, it also doesn't contribute to an increase in the concentration of any ion involved in the equilibrium reaction.