In paper manufacturing, degumming of the raw material is done using
- A.sulphuric acid
- B.bleaching powder
- C.caustic soda
- D.nitric acid
Correct answer
Explanation
The correct answer is C, caustic soda. In paper making the raw plant material is cooked with caustic soda, which dissolves the gums, resins and lignin that bind the cellulose fibres together.
Paper is made from cellulose fibres taken from wood, bamboo, grasses or rags. The chips are cooked under pressure with an alkaline solution of sodium hydroxide (caustic soda), often with sodium sulphide in the kraft process. This step, called pulping or degumming, breaks down the non-cellulose matter and frees the fibres as pulp. The pulp is then washed, bleached and pressed into sheets.
Option A is wrong because sulphuric acid would damage the cellulose and is not used to remove gums here. Option B is wrong because bleaching powder is used later to whiten the pulp, not to degum the raw material. Option D is wrong because nitric acid is a strong oxidising acid not used in pulping.
Exam tip: paper pulping or degumming uses caustic soda (NaOH); bleaching of the pulp is a separate later step.
Practice Questions
View allWhich one of the following is the 'energy currency' for cellular processes?
- A.Glucose
- B.ATP
- C.ADP
- D.Pyruvic acid
Show answer
Adenosine triphosphate stores energy in its phosphate bonds and releases it wherever the cell needs it, so it is called the energy currency of the cell.
Read the full explanation →Which one of the following is the correct reactivity order of metals reacting with dilute HCl?
- A.Mg > Al > Zn > Fe
- B.Mg < Al < Zn < Fe
- C.Mg > Zn > Fe > Al
- D.Fe > Mg > Al > Zn
Show answer
This is the order in which these metals stand in the reactivity series, and it matches how vigorously they release hydrogen from dilute hydrochloric acid.
Read the full explanation →Deficiency of iron causes
- A.Anaemia
- B.Scurvy
- C.Rickets
- D.Cholera
Show answer
Iron is needed to make haemoglobin, so too little iron means too little haemoglobin and a reduced ability of the blood to carry oxygen.
Read the full explanation →Consider the following statements regarding waves : 1. If the particles of a medium move along the direction of motion of the wave, the wave is called a longitudinal wave. 2. If the particles of a medium move perpendicular to the direction of motion of the wave, the wave is called a transverse wave. 3. Transverse waves may involve change in the shape of the medium, whereas longitudinal waves involve change in the density of the medium. Which of the statements given above is/are correct ?
- A.1 and 2 only
- B.1 only
- C.2 and 3 only
- D.1, 2 and 3
Show answer
All three statements correctly describe how particles move in the two kinds of mechanical waves. In a longitudinal wave, such as sound in air, the particles vibrate back and forth along the direction in which the wave travels.
Read the full explanation →When a piece of pure silicon is doped with aluminium, then
- A.the conductivity of the doped silicon piece will remain the same
- B.the doped silicon piece will become n-type
- C.the doped silicon piece will become p-type
- D.the resistivity of the doped silicon piece will increase
Show answer
Aluminium has three valence electrons, one fewer than silicon, so each aluminium atom leaves a hole that acts as a positive charge carrier.
Read the full explanation →