Problem 30 - Chemistry in 30 days

Question

Boric acid is prepared from borax by the action of \(\begin{array}{ll}\text { (a) Hydrochloric acid } & \text { (b) Sodium hydroxide }\end{array}\) (c) Carbon dioxide (d) Sodium carbonate Which does not exist?

Step-by-Step Solution

Answer

Sodium carbonate does not directly form boric acid from borax.

Step 1: Understanding the Reaction

To solve this exercise, we need to understand the chemical reaction for the formation of boric acid from borax. Borax, chemically known as sodium borate, reacts with a strong acid to form boric acid. The strong acid commonly used for this reaction is hydrochloric acid (HCl).

Step 2: Evaluating Each Option

Let's evaluate each option given in the question: - (a) Hydrochloric acid: This option is correct because borax reacts with hydrochloric acid to yield boric acid - (b) Sodium hydroxide: This is incorrect because sodium hydroxide is a base and will not yield boric acid from borax - (c) Carbon dioxide: This can react with borax under specific conditions to form boric acid through a complex process - (d) Sodium carbonate: This compound does not participate in the direct formation of boric acid from borax and hence 'does not exist' as a direct contributor in the process.

Step 3: Conclusion

The correct answer to the question is identifying which option does not result in boric acid formation. Sodium carbonate does not directly contribute to the formation of boric acid from borax.

Key Concepts

Borax Reaction

The reaction between borax and hydrochloric acid is fundamental in the preparation of boric acid. Borax is a naturally occurring mineral, also known as sodium borate. Its chemical formula is Na₂[B₄O₅(OH)₄]·8H₂O. When borax is treated with hydrochloric acid, a common strong acid, the reaction results in the formation of boric acid.

• Borax reacts by releasing borate ions (B₄O₇²⁻) into the solution.
• These borate ions then interact with hydrogen ions (H⁺) provided by hydrochloric acid.
• This reaction produces boric acid ( H₃BO₃) along with sodium chloride ( NaCl), as a byproduct.

The general chemical equation for this process is:\[\text{Na}_2\text{B}_4\text{O}_7 + 2\text{HCl} + 5\text{H}_2\text{O} \rightarrow 4\text{H}_3\text{BO}_3 + 2\text{NaCl}\]This reaction is crucial in industrial and laboratory settings for producing boric acid from borax.

Hydrochloric Acid

Hydrochloric acid (HCl) is a strong, corrosive acid that is widely used in chemical reactions. It is a solution of hydrogen chloride gas in water. When used in the preparation of boric acid from borax, its acidic properties play a vital role.

• It provides hydrogen ions ( H⁺), which are critical for converting borate ions from borax into boric acid.
• Hydrochloric acid's highly reactive nature makes it suitable for this process because it readily reacts with borax.
• Besides being effective, hydrochloric acid is also readily available and affordable, making it an ideal choice for this reaction.

The efficiency of hydrochloric acid in this chemical reaction ensures a consistent and reliable production of boric acid, which is used in various applications ranging from antiseptics to insecticides.

Sodium Carbonate

Sodium carbonate (Na₂CO₃), also known as soda ash or washing soda, is an alkaline compound. In the context of boric acid preparation from borax, it does not play a direct role.

• Sodium carbonate is not an acid, so it cannot provide the hydrogen ions necessary for converting borate to boric acid.
• In fact, sodium carbonate being a base could interfere with the reaction by neutralizing acids, which is counterproductive to the formation of boric acid.
• Therefore, in the process of forming boric acid from borax, sodium carbonate is not a suitable reagent.

Thus, it does not exist as a component in the reaction pathway when preparing boric acid from borax, highlighting that it should not be considered in the boric acid preparation process.