# Pulp & Paper Questions and Answers – Surface Tension and Sizing

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This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Surface Tension and Sizing”.

1. Identify the equation used to calculate pore sizes.

l2 = rty cosθ/2ŋ

a) Lucas
b) Wettability
c) Kelvin
d) Pascal

Explanation: Lucas used this equation to calculate pore sizes in paper based on the speed of the rise of organic liquids in paper strips. Lucas used organic liquids since they would not change the pore sizes by swelling or hydration.

2. Identify the equation to give actual capillary action.

Pα – Pβ= 2y / R

a) Lucas
b) Wettability
c) Kelvin
d) Pascal

Explanation: This equation is modified to give the actual capillary rise for H2O by solving for the force of H2O and the wettability of the glass by the H2O. If the H2O completely wets the glass. Here, r is the capillary tube radius, p is the density of a phase, g is the acc. due to gravity, and h is the height of the H2O.

3. Identify the equation to give actual capillary action.

y = 1/2(ρα – ρβ)ghr / cosθ

a) Lucas
b) Wettability
c) Kelvin
d) Pascal

Explanation: This equation is modified to give the actual capillary rise for H2O by solving for the force of H2O and the wettability of the glass by the H2O. If the H2O completely wets the glass. Here, r is the capillary tube radius, p is the density of a phase, g is the acc. due to gravity, and h is the height of the H2O.

4. 3 contact angles of a droplet on a flat surface a) True
b) False

Explanation: Either at 90 degrees or an acute angle or an obtuse angle. Contact angel is the angle, normally measured through the liquid, where a liquid–vapor interface contacts a solid surface.

5. Find the hidden term

if adhesive > cohesive then 0 degree <= θ <_________

a) 10 degrees
b) 180 degrees
c) 100 degrees
d) 90 degrees

Explanation: The contact angle is a measure of the adhesive force of the liquid with the surface relative to the cohesive forces in the liquid. It is generally measured through the liquid, where a liquid–vapour interface contacts a solid surface.

6. Find the hidden term

if adhesive > cohesive then 90 degree <= θ <_________

a) 10 degrees
b) 180 degrees
c) 100 degrees
d) 90 degrees

Explanation: The contact angle is a measure of the adhesive force of the liquid with the surface relative to the cohesive forces in the liquid. The angle, conventionally measured through the liquid, where a liquid–vapour interface contacts a solid surface.

7. _________ is easily wetted by H2O and, H2O on _________ gives a low contact angle that approaches zero; this causes the water to be drawn into the capillaries. [/expand] a) Starch
b) Lignin
c) Cellulose
d) Pulp

Explanation: Cellulose is easily wetted by H2O and, H2O on cellulose gives a low contact angle that approaches zero; this causes the H2O to be drawn into the capillaries.

8. Internal sizing agents are generally _________ materials. The polar portion attaches to the fiber or fines directly through a covalent bond or indirectly through a caustic element such as alum.
a) Amphoteric
b) Amphitaric
c) Non polar
d) Polar

Explanation: Internal sizing agents are generally amphipathic having polar and nonpolar moieties on the same molecule materials. The polar portion more importantly, it is chemically reactive attaches to the fiber or fines directly through a covalent bond.

9. Identify the equation used to calculate pore radius from which water will condense.

r = (2yV) / RT ln (po/p)

a) Lucas
b) Wettability
c) Kelvin
d) Pascal

Explanation: A water droplet with a (+ve) radius has a slightly higher vapor pressure than a flat surface of H2O. When with a (-ve) radius has a lower vapor pressure, which allows condensation to occur.

10. Inverse _________has been utilized to characterize surface energy; in pulp and paper this has been accomplished with treated and untreated pulps.
a) Gas chromatography
b) Silver test
c) Stone test
d) Sulfurication 