Question

In the pulp and paper industry, the Kraft process uses which chemical for pulping?

• A. Calcium bisulfite
• B. Sodium hydroxide and sodium sulfide
• C. Sulfuric acid
• D. Ammonium hydroxide

Hint:

Memory Tip: Kraft process = White liquor = NaOH + Na$_2$S.

Answer 1

The Correct Option is B

Concept:
The Kraft process is the most common chemical pulping method used to separate cellulose fibers from wood by dissolving lignin.

Step 1:
Wood contains cellulose fibers bound together by lignin. Pulping removes lignin and frees the fibers.

Step 2:
The cooking liquor in the Kraft process mainly contains sodium hydroxide (NaOH) and sodium sulfide (Na$_2$S).

Step 3:
These chemicals break down lignin while preserving useful cellulose fibers.

Step 4:
Calcium bisulfite belongs to sulfite process, while sulfuric acid and ammonium hydroxide are not standard Kraft pulping chemicals.

Step 5:
Hence, the Kraft process uses sodium hydroxide and sodium sulfide.