Question

Which of the following statements is correct? (a) Sodium carbonate decomposes on heating (b) Sodium bicarbonate is more soluble in water than potassium bicarbonate. (c) Sodium when heated with excess of \(\mathrm{O}_{2}\) gives peroxide. (d) Lithium halides are highly ionic in nature.

Short answer

(c) Sodium when heated with excess of \text{O}_{2} gives peroxide.

Step-by-step solution

Analyze Option (a)

To assess if sodium carbonate decomposes on heating, recall its stability and the products formed upon heating. Sodium carbonate ((Na_2CO_3)) decomposes to form sodium oxide ((Na_2O)) and carbon dioxide ((CO_2)) upon strong heating.

Analyze Option (b)

To determine the solubility, refer to general solubility trends of group 1 carbonates and bicarbonates in water. Sodium bicarbonate ((NaHCO_3)) is less soluble in water than potassium bicarbonate ((KHCO_3)), considering that the solubility decreases from Li to Cs in the group 1 metals.

Analyze Option (c)

Examine the reaction of sodium with oxygen. When sodium is heated with excess oxygen, sodium peroxide ((Na_2O_2)) is formed. This reaction is characteristic of group 1 elements.

Analyze Option (d)

Consider the nature of lithium halides. Among alkali metal halides, lithium halides tend to have significant covalent character due to lithium's small ionic size and relatively high charge density, making them less ionic than the halides of other alkali metals.

Key concepts

Sodium Carbonate Decomposition

Understanding the breakdown of sodium carbonate ((Na_2CO_3)) is fundamental in inorganic chemistry. Upon strong heating, this compound undergoes thermal decomposition to form sodium oxide ((Na_2O)) and carbon dioxide ((CO_2)). This reaction is an example of a decomposition reaction, a type of chemical reaction where a single compound breaks down into two or more simpler substances under certain conditions, such as high temperature. The decomposition of sodium carbonate is particularly important in various industrial processes, including glass making and as a preliminary step in the Solvay process for producing sodium carbonate itself.

Through this decomposition, one can observe how heat energy affects the stability of chemical compounds, causing them to break their chemical bonds and form new substances.

Solubility Trends in Group 1 Elements

The solubility of compounds formed by group 1 elements in water exhibits certain trends owing to the atomic and ionic properties of these elements. Typically, as we move down the group from lithium to cesium, the ionic size increases, resulting in a decrease in lattice energy and an increase in the solubility of the group 1 carbonates and bicarbonates. Thus, sodium bicarbonate ((NaHCO_3)) is less soluble in water compared to potassium bicarbonate ((KHCO_3)), aligning with the general solubility trend.

This principle is critical in predicting the behavior of these compounds in aqueous solutions and plays a significant role in industrial applications such as water softening, where the solubility of certain ions is of utmost importance.

Sodium Peroxide Formation

The formation of sodium peroxide ((Na_2O_2)) occurs when sodium is heated with an excess of oxygen. This reaction highlights the reactive nature of group 1 elements with oxygen. Sodium's vigorous reaction with oxygen to form peroxide can be linked to its relatively low ionization energy, which allows it to readily give up its valence electron and react with oxygen.

In a laboratory setting, sodium peroxide acts as an oxidizing agent and is utilized in bleaching and deodorizing processes, as well as in chemical synthesis. Knowledge of such reactions is not only academically significant but also essential in the context of safe handling and use of reactive group 1 metals.

Ionic and Covalent Character of Lithium Halides

Lithium halides, when compared to other alkali metal halides, possess a noticeable covalent character. This is primarily due to lithium's small ionic radius and high charge density, which leads to the polarization of anion from the halide and partial sharing of electron density between the lithium and halide ions.

As such, lithium halides do not exhibit the highly ionic traits typical of other group 1 halides but rather possess characteristics closer to that of covalent compounds. Understanding the nature of these bonds is crucial in predicting the properties of these substances, including their melting points, solubility, and their behavior in different chemical reactions.