Food Packaging Technology Multiple Choice Questions & Answers (MCQs) on “Chemical Pulping & Semichemical Pulp”.
1. Chemical pulping mostly uses which of the following chemical?
a) Sodium Nitrate
b) Potassium Hydroxide
c) Calcium Carbonate
d) Sodium Hydroxide
Answer: d
Clarification: All chemical pulping methods are based, either directly or indirectly, on the use of sodium hydroxide. The chemical is selectively chosen, because, the nature of the pulping chemicals influences the properties of the residual lignin and the residual carbohydrates.
2. The primary goal of chemical pulping is to selectively remove as much lignin as possible.
a) True
b) False
Answer: a
Clarification: The given statement is true. The primary goal of chemical pulping is to selectively remove as much lignin as possible, especially from the middle lamella, without degrading the carbohydrate components and negatively effecting pulp properties.
3. The kappa number of bleachable softwood pulps is _______
a) 10-20
b) 20-30
c) 30-40
d) 40-50
Answer: c
Clarification: The kappa number of bleachable softwood pulps is 30–40. The pulp and paper industry uses the “kappa number” to express the lignin content of a pulp, a high kappa number indicating high lignin content.
4. The kappa number of bleachable hardwood pulps is ________
a) 20–30
b) 30–40
c) 10–20
d) 18–20
Answer: d
Clarification: The kappa number of bleachable hardwood pulps is 18–20. This indicates that hardwood pulp has lower lignin content than softwood pulp. Lignin does not have fiber forming properties, hence, hardwood pulp does not make as strong paper as softwood pulp.
5. Chemical pulping method uses acid for the process.
a) True
b) False
Answer: b
Clarification: The given statement is false. Chemical pulping method uses alkali for the process. It includes- soda process, kraft process and sulfite process, all of which used sodium hydroxide (alkali) either directly or indirectly.
6. Kraft process is also known as ______
a) Soda process
b) Sulphate process
c) Sulphite process
d) Semichemical process
Answer: b
Clarification: Kraft process is also known as sulphate process. It is commonly called kraft, because it is the German and Swedish word for strength. The new sulfate process produced a much stronger pulp than that from the soda process.
7. Which of the following is also known as the white liquor?
a) Sodium hydroxide and Sodium hydride
b) Sodium sulphite and Sodium sulphate
c) Sodium sulphate and Sodium hydroxide
d) Sodium hydride only
Answer: a
Clarification: A solution of sodium hydroxide and sodium hydride is also known as the white liquor. It is widely used in the chemical pulping industry for cooking the wood chips, hence, also called cooking liquor.
8. Which of the following was the first alkaline process to be developed?
a) Soda process
b) Sulphate process
c) Sulphite process
d) Kraft process
Answer: a
Clarification: Soda process was the first alkaline process to be developed. It was invented by Englishmen Hugh Burgess and Charles Watt in 1851 and was patented in 1854. The first successful soda mill commenced operation in 1866.
9. The soda process consisted of boiling wood _____ in sodium hydroxide liquor.
a) 1%–2%
b) 3%–5%
c) 2%–3%
d) 4%–6%
Answer: d
Clarification: The soda process consisted of boiling wood in 4%–6% sodium hydroxide liquor at a high temperature (170°C). This process is now obsolete. Less than 2% of the pulp produced today uses this process which is very similar to the sulfate process, except that only sodium hydroxide is used. Essentially all former soda mills have converted to the sulfate process.
10. Kraft Process was developed in the year _____
a) 1750
b) 1850
c) 1879
d) 1995
Answer: c
Clarification: In 1879, German chemist Carl F. Dahl developed the Kraft (sulfate) method of pulping wood. The process was essentially a modification of the soda process, but instead of sodium hydroxide, sodium sulfate was the major chemical used as the cooking liquor.
11. ‘Dissolving pulp” is obtained by which of the following methods?
a) Semichemical process
b) Sulphite process
c) Kraft process
d) Soda process
Answer: b
Clarification: ‘Dissolving pulp” is obtained by sulphite process. It is a special grade of bleached sulfite pulp and is used for a variety of cellulose derivatives including RCF and cellulose acetate.
12. Which of the following methods is mostly used for making glassine?
a) Soda process
b) Kraft process
c) Semichemical process
d) Sulphite process
Answer: d
Clarification: Sulphite process is mostly used for making glassine. It is also used as a source of cellulose for non-paper applications. It is because sulfite pulps have higher brightness, higher yields at a given kappa, lower odor and lower investment costs as compared to kraft pulps.
13. Several pulping processes are based on the use of sulfur dioxide as the essential component of the pulping liquor.
a) True
b) False
Answer: a
Clarification: The given statement is true. Several pulping processes are based on the use of sulfur dioxide as the essential component of the pulping liquor. Sulfur dioxide dissolves in water to form sulfurous acid, and a part of the acid is neutralized by a base during preparation of the pulping liquor. The various sulfite processes differ in the kind of base used and in the amount of base added. These differences govern the resulting acidity or pH of the liquor. These processes depend on the ability of sulfite solutions to render lignin partially soluble.
14. Semichemical method of pulping involves mechanical pulping followed by chemical pulping.
a) True
b) False
Answer: b
Clarification: The given statement is false. Semichemical pulping combines chemical and mechanical methods in which wood chips are partially softened or digested with conventional chemicals, such as sodium hydroxide, sodium carbonate or sodium sulfate, after which the remainder of the pulping action is supplied mechanically, most often in disk refiners.
15. The _______ uses sodium sulfite and a small amount of sodium hydroxide or sodium carbonate to give slightly alkaline liquor.
a) Basic-sulfite semichemical (NSSC) process
b) Acidic-sulfite semichemical (NSSC) process
c) Neutral-sulfite semichemical (NSSC) process
d) Alkaline-sulfite semichemical (NSSC) process
Answer: c
Clarification: The neutral-sulfite semichemical (NSSC) process (applied mainly to hardwood chips) uses sodium sulfite and a small amount of sodium hydroxide or sodium carbonate to give slightly alkaline liquor. The NSSC pulp is obtained in higher yield but with higher lignin content than in the other sulfite processes. It is used mainly for the manufacture of corrugating medium.