Question

The incorrect statement among the following is: (1) beryllium oxide is amphoteric in nature (2) solubility of sulphates of second group elements decreases down the group (3) reducing power of hydride of alkali metal decreases down the group (4) Berylium has diagonal relationship with alumunium

Short answer

Statement 3 is incorrect.

Step-by-step solution

- Understand the statements

Carefully read each of the four statements provided in the question. Determine what each statement claims about the properties and trends in the given chemical elements.

- Analyze statement 1

Statement 1: 'beryllium oxide is amphoteric in nature'. Amphoteric substances can react with both acids and bases. Beryllium oxide (BeO) is known to exhibit such properties. Therefore, statement 1 is correct.

- Analyze statement 2

Statement 2: 'solubility of sulphates of second group elements decreases down the group'. The solubility of sulphates of Group 2 elements (such as MgSO4, CaSO4, and BaSO4) generally decreases as you move down the group. Therefore, statement 2 is correct.

- Analyze statement 3

Statement 3: 'reducing power of hydride of alkali metal decreases down the group'. The reducing power of alkali metal hydrides (such as LiH, NaH, and KH) actually increases down the group because the larger alkali metals form stronger hydrides. Therefore, statement 3 is incorrect.

- Analyze statement 4

Statement 4: 'Beryllium has diagonal relationship with aluminum'. Beryllium (in Group 2) and aluminum (in Group 13) share some similar chemical properties due to this diagonal relationship. Therefore, statement 4 is correct.

- Conclusion

Based on the analysis, the incorrect statement among the provided options is determined. This incorrect statement must disagree with general chemical properties or trends.

Key concepts

Amphoteric Oxides

Amphoteric oxides are substances that can react both with acids and bases to form salts and water. A classic example is beryllium oxide (BeO).
Beryllium oxide exhibits dual behavior; it acts as a base when reacting with acids and as an acid when reacting with bases. This characteristic makes BeO amphoteric.
For instance, when BeO reacts with hydrochloric acid (HCl), it forms Beryllium Cloride (BeCl₂) and water. Conversely, when BeO reacts with sodium hydroxide (NaOH), it forms sodium beryllate (Na₂BeO₂) and water. This concept extends to other elements and compounds that can 'flexibly' react with both acids and bases.

Solubility Trends in Group 2 Elements

Understanding the solubility trends can often help to predict the behavior of compounds in chemistry. For Group 2 elements, like magnesium (Mg), calcium (Ca), and barium (Ba), the solubility of their sulfates decreases as you move down the group.
This trend is due to lattice energy and hydration energy.
1. Lattice Energy: The energy required to separate the ions in a crystal lattice.
2. Hydration Energy: The energy released when ions are surrounded by water molecules.
For lighter Group 2 elements, the hydration energy outweighs the lattice energy, making them more soluble. For heavier ones like BaSO₄, lattice energy is more significant, thus decreasing their solubility.
Understanding these trends helps predict solubility behavior, which is often crucial for practical and theoretical applications.

Reducing Power of Alkali Metal Hydrides

Reducing power refers to the ability of a substance to donate electrons in a chemical reaction. For alkali metal hydrides, the reducing power increases as you go down the group in the periodic table.
This is contrary to other trends you've seen where properties might decrease down a group. The reason for this trend lies in the size and reactivity of the atoms involved.
- As you move down the group, alkali metals like lithium (LiH), sodium (NaH), and potassium (KH) become larger.
- Larger atoms have electrons that are more loosely held, making them better reducing agents.
Therefore, KH has a higher reducing power compared to NaH, and NaH has a higher reducing power than LiH. This pattern is important to recognize, especially when dealing with redox reactions and electrochemical processes.

Diagonal Relationship in the Periodic Table

In the periodic table, diagonal relationships occur between certain pairs of elements in adjacent groups and periods, for example, between beryllium (Be) in Group 2 and aluminum (Al) in Group 13.
Despite their different group positions, these elements share some similar properties.
- Both Be and Al form oxides that are amphoteric.
- Both form covalent compounds rather than ionic.
This similarity arises because of the comparable charge density and ionic radii, despite residing in different groups.
Understanding these diagonal relationships helps in predicting properties and behaviors of elements that might otherwise seem different.