Explanation:
The van't Hoff factor (i) is the ratio between the actual number of particles in a solution and the number of formula units that are dissolved or dissociated in the solution. It is defined as the ratio of the moles of solute particles in solution to the moles of solute dissolved.

The van't Hoff factor for K[Fe(CN)6] is 2, as it dissociates into two ions (K+ and [Fe(CN)6]3-) in water. We need to find a salt that also has the same van't Hoff factor.

Let's check the given options one by one:

a) Al(SO4)3: When Al(SO4)3 dissolves in water, it dissociates into Al3+ and 3SO42- ions. Therefore, the van't Hoff factor for Al(SO4)3 is 4 (1 + 3). This option is incorrect.

b) NaCl: NaCl dissolves in water to give Na+ and Cl- ions. Therefore, the van't Hoff factor for NaCl is 2 (1 + 1). This option is incorrect.

c) Al(NO3)3: When Al(NO3)3 dissolves in water, it dissociates into Al3+ and 3NO3- ions. Therefore, the van't Hoff factor for Al(NO3)3 is 4 (1 + 3). This option is incorrect.

d) Na2SO4: Na2SO4 dissolves in water to give 2Na+ and SO42- ions. Therefore, the van't Hoff factor for Na2SO4 is 3 (2 + 1). This option is incorrect.

Therefore, the correct option is (a) Al(SO4)3.

Note: K[Fe(CN)6] and Al(SO4)3 are both ionic compounds, but Al(SO4)3 dissociates into four ions (Al3+ and 3SO42-) in water, which gives a van't Hoff factor of 4, while K[Fe(CN)6] dissociates into two ions (K+ and [Fe(CN)6]3-) in water, which gives a van't Hoff factor of 2. The reason for this difference is that Al(SO4)3 is a salt that can undergo hydrolysis (reaction with water) to form acidic solutions, which increases the number of ions in solution.