Question

Boric acid is prepared from the borax by the action of (1) hydrochloric acid (2) sodium hydroxide (3) carbon dioxide (4) sodium carbonate

Short answer

Hydrochloric acid (1)

Step-by-step solution

Identify Reaction Requirements

Determine what borax and boric acid are chemically. Borax is chemically represented as \( \text{Na}_2\text{B}_4\text{O}_7 \bullet 10\text{H}_2\text{O} \) and boric acid as \( \text{H}_3\text{BO}_3 \).

Understand Possible Reactions

List the possible reactions with each given reagent. For hydrochloric acid: \( \text{Na}_2\text{B}_4\text{O}_7 \bullet 10\text{H}_2\text{O} + 2\text{HCl} \rightarrow 4\text{H}_3\text{BO}_3 + 2\text{NaCl} + 5\text{H}_2\text{O} \). Check if the other reagents can also produce boric acid.

Verify the Correct Reaction

Review the reactions to determine which one leads to the creation of boric acid. The reaction with hydrochloric acid produces boric acid directly.

Select the Correct Answer

Based on the reactions, confirm that the correct reagent to produce boric acid from borax is hydrochloric acid.

Key concepts

borax

Borax is an essential mineral that you need to understand while preparing boric acid. Chemically, borax is represented as \(\text{Na}_2\text{B}_4\text{O}_7 \bullet 10\text{H}_2\text{O}\). This means it is composed of sodium, boron, oxygen, and water. Borax is often used in cleaning products, glass manufacturing, and even in the production of cosmetics. When you dissolve borax in water, it breaks down into borate ions (\(\text{B}_4\text{O}_7^{2-}\)), sodium ions (\(\text{Na}^+\)), and water molecules. This setup is critical to the chemical reaction where boric acid will be produced.

hydrochloric acid

Hydrochloric acid (HCl) is a strong acid and plays a significant role in preparing boric acid from borax. When borax reacts with hydrochloric acid according to the equation: \(\text{Na}_2\text{B}_4\text{O}_7 \bullet 10\text{H}_2\text{O} + 2\text{HCl} \rightarrow 4\text{H}_3\text{BO}_3 + 2\text{NaCl} + 5\text{H}_2\text{O}\), it produces boric acid (\text{H}_3\text{BO}_3), sodium chloride (\text{NaCl}), and water (\text{H}_2\text{O}). This reaction is straightforward and efficient because hydrochloric acid provides the necessary hydrogen ions (H\(^+\)), which bond with borate to form boric acid. This is why hydrochloric acid is chosen over other substances like sodium hydroxide or carbon dioxide.

chemical reactions

Understanding chemical reactions is pivotal for this exercise. A chemical reaction involves the transformation of reactants into products. In preparing boric acid, the reaction between borax and hydrochloric acid is an excellent example. The reactants—borax and hydrochloric acid—undergo a chemical change to produce boric acid, sodium chloride, and water. The equation: \(\text{Na}_2\text{B}_4\text{O}_7 \bullet 10\text{H}_2\text{O} + 2\text{HCl} \rightarrow 4\text{H}_3\text{BO}_3 + 2\text{NaCl} + 5\text{H}_2\text{O}\) demonstrates this transformation clearly. Recognizing the formation, breakdown, and rearrangement of bonds helps in predicting product formation in chemical reactions.

engineering entrance exams

Grasping the concept of boric acid preparation from borax is important for engineering entrance exams. These exams test your understanding of fundamental chemical reactions and processes. Knowing the correct reagent, in this case, hydrochloric acid, showcases your ability to apply theoretical knowledge practically. Engineering exams often include similar problems requiring you to identify proper reagents, predict products of reactions, and balance chemical equations. These concepts are the building blocks of more complex topics in chemistry and engineering. Practicing such exercises diligently can improve your problem-solving skills and confidence during exams.