Question

The coagulation values in millimoles per litre of the electrolytes used for the coagulation of $A{s_2}{S_3}$ are given below:
I. $(NaCl) = 52$ II. $(BaC{l_2}) = 0.69$ III. $(MgS{O_4}) = 0.22$
The correct order of their coagulating power is:
A) $III > II > I$
B) $III > I > II$
C) $I > II > III$
D) $II > I > III$

Answer 1

Hint: The coagulation value can be elaborated as the number of millimoles of an electrolyte which are required to bring the coagulation of about one litre of solution. The coagulation power is its capacity to form coagulation. So one can apply these concepts for the given value and decide the correct order.

Complete step by step answer:
1) First of all let us discuss the concept of coagulation where it is a process in which colloidal particle are aggregated together to make them into large-sized particles which get settled as a precipitate at the bottom of the solution.
2) Now let us discuss the concept of coagulation value where it can be defined as the minimum concentration of an electrolyte required to cause the coagulation. Hence, from this, we can say that for ${\text{NaCl}}$ molecule ${\text{52}}$ coagulating value is needed to form coagulation and this applies the same for the other molecules.
3) The value of coagulation power is always inversely proportional to the coagulation value which means the greater the coagulation value of a compound the smaller will be its coagulation power and vice versa.
4) As the molecule ${\text{NaCl}}$ has a coagulation value ${\text{52}}$ which is the highest in all the values given in the question, it will have the lowest coagulation power amongst all of them and the molecule $MgS{O_4}$ will have the highest coagulation power.
5) Therefore, the correct order of coagulation power will be $MgS{O_4} > BaC{l_2} > NaCl$ which shows the option A as a correct choice.

So, the correct answer is Option A .

Note:
One should always remember that the coagulation of particles in a colloidal solution by an electrolyte presence will not take place until the electrolyte which has been added has a certain minimum concentration required in the solution. According to the Hardy-Schulze rule if the valency of the active ion is greater than its coagulating power will be greater i.e. directly proportional.