This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Pulp Bleaching”.
1. Bleaching is the treatment of wood (and other lignocellulosic) pulps with chemical agents to decrease their brightness.
a) True
b) False
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Explanation: Bleaching is the treatment of wood (and other lignocellulosic) pulps with chemical agents to increase their brightness.
2. Bleaching of chemical pulps is achieved by lignin addition.
a) True
b) False
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Explanation: Bleaching of chemical pulps is achieved by lignin removal.
3. _________ removal in chemical pulps leads to higher fiber-fiber bonding strength in paper, but the strong chemical pulps decrement in the length of cellulose molecules, resulting in weaker fibers.
a) Softwood
b) Hardwood
c) Lignin
d) Pulp
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Explanation: Lignin removal in chemical pulps leads to higher fiber-fiber bonding strength in paper, but the strong chemical pulps decrement in the length of cellulose molecules, resulting in weaker fibers.
4. Bleaching mechanical pulps is called _________ to distinguish it from bleaching of chemical pulps.
a) Brightening
b) Bloating
c) Blackening
d) Branding
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Explanation: Bleaching mechanical pulps is called brightening to distinguish them from the bleaching of chemical pulps.
5. Brightness is a term used to describe the _________ of pulp or paper, on a scale from 0 to 100.
a) Whiteness distribution
b) Whitness obstructivness
c) Coquettes
d) Bleach
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Explanation: Brightness is a term used to describe the whiteness distribution of pulp or paper, on a scale from 0 to 100.
6. _________ is the yellowness of pulps on exposure to air, light, heat, and fungi due to modification of residual lignin forming chromophores.
a) Colour reversion
b) Colour addition
c) Oxidation
d) Exposure
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Explanation: Colour reversion is the yellowness of pulps on exposure to air, light, heat, and fungi due to modification of residual lignin forming chromophores.
7. _________ pulps are susceptible to colour reversion.
a) Chemical
b) Mechanical
c) Dithionite
d) Hydrousulfite
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Explanation: Mechanical pulps are particularly susceptible to colour reversion, though chemical pulps may experience this when exposed to high temperatures.
8. _________ pulps are not susceptible to colour reversion.
a) Chemical
b) Mechanical
c) Dithionite
d) Hydrousulfite
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Explanation: Mechanical pulps are particularly susceptible to colour re-version, though chemical pulps may experience this when they are exposed to high temperatures.
9. Bleaching stages are carried out consistencies for pulp bleaching are from _________%.
a) 8-10
b) 3-20
c) 3-10
d) 4-15
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Explanation: Bleaching stages are carried out under consistencies from 3-20%. Higher consistencies of 10-20% are used with chemicals such as oxygen, peroxide, and HOCl, which react with lignin slowly.
10. Higher bleaching stages are carried out in consisitencies of range____________
a) 8-10
b) 10-20
c) 15-20
d) 3-10
View Answer
Explanation: Bleaching stages are carried out consistencies from 3-20%. Higher consistencies of 10-20% are used with chemicals such as oxygen, peroxide, and hypochloride, which react with lignin slowly.
Sanfoundry Global Education & Learning Series – Pulp and Paper.
To practice all areas of Pulp and Paper, here is complete set of 1000+ Multiple Choice Questions and Answers.
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