Answer to Question #213042 in General Chemistry for Alaa Aboukhadra

Question

For a reaction system at chemical equilibrium that contains a slightly insoluble salt

the coefficients are always one

sp stand for special precipitate

K_SP always contain the concentration of water as a component

K_SP always contain the concentration of a solid as a component

the reaction is always shifted to the towards the direction for formation of the solid if the concentration of cationic species increases

the reaction is always shifted to the towards the direction for formation of the solid if more solid is added to the system

the coefficients are not always one

sp stand for solubility product

Answer 1

Given : System of chemical equilibrium that contains a slightly insoluble salt:-

1) The coefficients are always one: This is incorrect as the coefficient of ions will depend on the chemical formula of the compound.

For example, in the case of PbI₂, the coefficient of I^- will be 2 and that of Pb²⁺will be 1 as per the reaction.

=> PbI₂ (s) -------> Pb²⁺ (aq) + 2 I^- (aq)

2) sp stands for special precipitate: This is also incorrect as sp stands for solubility product.

3) K_SP always contains the concentration of water as a component: This is also incorrect as the concentration of liquid water is not considered in the equilibrium constant expression.

4) K_SP always contains the concentration of a solid as a component: This is also incorrect as the concentration of solid water is not considered in the equilibrium constant expression.

5) the reaction is always shifted towards the direction for the formation of the solid if the concentration of cationic species increases: 

Since on increasing the concentration of the cationic species, the concentration in the product side will increase.

And according to LeChatelier's principle, the reaction equilibrium shifts in the direction where the change made can be compensated.

Hence to compensate for the increment in the concentration of cationic species and hence on the product side, the reaction equilibrium will shift towards the reactant side forming solid.

Hence this is the correct statement.

6) the reaction is always shifted towards the direction for the formation of the solid if more solid is added to the system:

Since solid component concentration does not affect the equilibrium constant.

Hence the equilibrium will not get shifted towards any side on adding more solid.

Hence this is also an incorrect statement.

7) the coefficients are not always one: This is correct as discussed in point 1.

8) sp stands for solubility product: This is correct as sp stands for solubility product.