Step 1: Colligative Property Fundamentals
- Colligative properties are determined by the quantity of particles in a solution, not their chemical identity.
- The van't Hoff factor (\(i\)) quantifies the dissociation of a molecule into ions.
Step 2: Ion Calculation for Dissociation
BaCl$_2$ yields 3 ions: one Ba$^{2+}$ and two Cl$^-$.
AgNO$_3$ yields 2 ions: one Ag$^+$ and one NO$_3^-$.
Urea is a non-dissociating solute, thus \( i = 1 \).
(NH$_4$)$_3$PO$_4$ yields 4 ions: three NH$_4^+$ and one PO$_4^{3-}$.
Step 3: Determining the Greatest Colligative Effect
A higher ion count leads to more pronounced colligative properties.
(NH$_4$)$_3$PO$_4$, producing 4 ions, exhibits the most significant colligative effect.
Therefore, the correct designation is (D).
A particle is moving in a straight line. The variation of position $ x $ as a function of time $ t $ is given as:
$ x = t^3 - 6t^2 + 20t + 15 $.
The velocity of the body when its acceleration becomes zero is: