Question

The chemical formula of Glauber's salt, used in the Kraft process, is

• A. Na$_2$CO$_3$.10H$_2$O
• B. Na$_2$S$_2$O$_4$.2H$_2$O
• C. Na$_2$HPO$_4$.2H$_2$O
• D. Na$_2$SO$_4$.10H$_2$O

Hint:

Glauber's salt, or sodium sulfate decahydrate, is used in industrial processes like the Kraft pulping method for breaking down lignin and separating cellulose.

Answer 1

The Correct Option is D

Glauber's salt is a well-known chemical compound used in the Kraft process, which is the primary method for making paper and pulp. The salt is specifically a hydrated form of sodium sulfate and has the chemical formula Na$_2$SO$_4$.10H$_2$O. It is commonly referred to as sodium sulfate decahydrate because of the ten water molecules in its crystalline form.

Step 1: Understanding the Role of Glauber's Salt in the Kraft Process.
The Kraft process is widely used in the paper industry to separate the cellulose fibers from lignin in wood. Glauber's salt (sodium sulfate decahydrate) is used in the pulping process as it helps break down the lignin, thus facilitating the separation of the cellulose fibers which are later used to make paper.

Step 2: Identifying the Formula of Glauber's Salt.
In terms of chemical structure, Glauber's salt is a sodium sulfate compound (Na$_2$SO$_4$) with ten water molecules attached, making it Na$_2$SO$_4$.10H$_2$O. The water molecules are part of the crystal lattice, which gives it the decahydrate designation. This hydration is crucial for its effectiveness in industrial applications.

Step 3: Conclusion.
Therefore, the correct formula for Glauber's salt used in the Kraft process is Na$_2$SO$_4$.10H$_2$O, which corresponds to option (D).

Final Answer: Na$_2$SO$_4$.10H$_2$O