To determine which compound would be most effective in lowering the melting point of ice on roads, we need to consider the colligative properties of the compounds. Colligative properties depend on the number of particles in a solution, not the nature of the particles. One of the key properties influenced by the number of dissolved particles is the melting point depression (how much the melting point is lowered).
Let's examine each compound based on its dissociation in water:
1. NaCl (Sodium Chloride):
- Dissociation: NaCl dissociates into two ions: [tex]\( \text{Na}^+ \)[/tex] and [tex]\( \text{Cl}^- \)[/tex].
- Total Ions Produced: 2 ions.
2. [tex]\( KNO_3 \)[/tex] (Potassium Nitrate):
- Dissociation: [tex]\( KNO_3 \)[/tex] dissociates into two ions: [tex]\( \text{K}^+ \)[/tex] and [tex]\( \text{NO}_3^- \)[/tex].
- Total Ions Produced: 2 ions.
3. [tex]\( C_6H_{12}O_6 \)[/tex] (Glucose):
- Dissociation: [tex]\( C_6H_{12}O_6 \)[/tex] does not dissociate in water. It remains as one molecule. It's a non-electrolyte.
- Total Ions Produced: 0 ions.
4. [tex]\( CaCl_2 \)[/tex] (Calcium Chloride):
- Dissociation: [tex]\( CaCl_2 \)[/tex] dissociates into three ions: [tex]\( \text{Ca}^{2+} \)[/tex] and 2 [tex]\( \text{Cl}^- \)[/tex].
- Total Ions Produced: 3 ions.
The effectiveness of each compound in lowering the melting point of ice is proportional to the number of ions it produces when it dissociates in water. The more ions produced, the greater the melting point depression.
- NaCl produces 2 ions.
- [tex]\( KNO_3 \)[/tex] produces 2 ions.
- [tex]\( C_6H_{12}O_6 \)[/tex] produces 0 ions.
- [tex]\( CaCl_2 \)[/tex] produces 3 ions.
Since [tex]\( CaCl_2 \)[/tex] produces the most ions (3 ions), it will be the most effective in lowering the melting point of ice.
Thus, the correct answer is:
d. [tex]\( CaCl_2 \)[/tex]
