Problem 1 - A Complete Resource Book in Chemistry for JEE Main

Question

Which is more soluble in water? (a) \(\mathrm{AgI}\) (b) \(\mathrm{AgF}\) (c) \(\mathrm{AgBr}\) (d) \(\mathrm{AgCl}\)

Step-by-Step Solution

Answer

Silver fluoride ( 6AgF) is the most soluble in water.

Step 1: Understand Solubility of Silver Halides

Silver halides are compounds that consist of silver ions and halide ions. The solubility of these compounds in water generally decreases as the halide ion gets larger.

Step 2: Identify Trend in Halide Compounds

In silver halides, fluorides and chlorides are typically more soluble in water, whereas bromides and iodides have much lower solubility. This means that as you move down the halide group in the periodic table, the solubility of silver halide compounds decreases.

Step 3: Order the Compounds by Solubility

Based on the general trend, arrange the given silver halides in order of solubility: AgF, AgCl, AgBr, AgI. This order correlates with the size of the halide ions; smaller halides like fluoride result in more soluble compounds.

Step 4: Determine the Most Soluble Compound

From the arranged order, it is clear that silver fluoride ( 6AgF) is the most soluble in water. Magnesium fluoride possesses the smallest halide ion, and this significantly increases its ability to dissolve in water.

Key Concepts

Solubility Trends

The solubility of silver halides in water is a fascinating topic in chemistry, driven by clear patterns along the periodic table. As we examine the solubility trends, we realize that solubility decreases as we move down the halide group. This trend is due to changes in the halide ion size. At the top of the group, silver fluoride (AgF) shows the greatest solubility. As you move down to silver chloride (AgCl), followed by silver bromide (AgBr), and finally silver iodide (AgI), solubility decreases. These trends occur because smaller halides are more capable of maintaining interactions with water molecules, facilitating better dissolution. Understanding these trends helps us predict which substances might be more soluble and gives insight into the chemistry of solutions.

Silver Halides

Silver halides are compounds formed between silver ions (Ag⁺) and halide ions. Each compound exhibits unique properties determined largely by the identity of the halide ion. Common silver halides include:

• Silver fluoride (AgF)
• Silver chloride (AgCl)
• Silver bromide (AgBr)
• Silver iodide (AgI)

These compounds are utilized in different applications due to their distinct characteristics. For example, silver chloride is well-known for its application in photographic processes, while silver iodide is used for cloud seeding in weather modification. The solubility of these compounds is influenced not only by the nature of the halide ion but also by the lattice energy of the crystals formed and the hydration energy released when the compound dissolves.

Halide Ion Size

The size of the halide ion plays a crucial role in determining the solubility of silver halides. As you move from fluoride to iodide in the periodic table, the size of the halide ion increases.

• Fluoride (F⁻) is the smallest.
• Chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻) are progressively larger.

Larger ions like bromide and iodide form silver halides that are less soluble because their bigger size leads to stronger lattice energy. This means they form stronger ionic bonds that are harder for water molecules to break apart. In contrast, smaller ions like fluoride create weaker lattice structures. The reduced energy required to separate these ions allows them to dissolve more easily in water. Understanding this size-solubility relationship is crucial for predicting the behavior of silver halides in various environments.