Exam 2 Flashcards

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0
Q

Which of the following has a surface excess more than the bulk? What happens to the surface tension for the solution?

A) NaCl; surface tension decreases
B) KOH; Surface tension increases
C) CH3(CH2)11OSO3Na ; increases
D) CH3(CH2)11(OCH2CH2)nOH ; decreases

A

D) surfactant, decreases

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1
Q

What is the name of the condition when competitive growth will precipitate out larger particles drawing material from smaller particles due to minimization of surface energy?

A

Ostwald Ripening

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2
Q

What is the temperature where a non-ionic surfactant’s solubility decreases and turbidity is observed?

A

Cloud Point Temperature

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3
Q

Which of the following will cause surface tension to decrease?

a) Lowering the temperature
b) Addition of surfactant
c) Addition of salt like NaCl
d) Increasing the temperature
e) A and B only
f) A and C only
g) C and D only
h) B and D only
i) B, C, and D only

A

h

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4
Q

If a quantum confined nanoparticle’s radius increases, what type of photon is necessary to promote an optical excitation equal to its bandgap energy compared to the original nanoparticle? (Energy and Wavelength)

A

Lower energy, longer wavelength photon

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5
Q

Which of the following properties for a single composition nanoparticle will increase compared to a bulk particle (one at macro size)?

a) Surface Energy
b) Melting Point temperature
c) Bandgap
d) All of the above
e) A and C only

A

e

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6
Q

What happens to surface tension at a concentration greater than the CMC for a pure, single component surfactant?

A

Stays the same

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7
Q

What term refers to the act of two particles coming together and not increasing the overall SA appreciably?

A

Aggregation

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8
Q

Which techniques are used to determine the size of typical Quantum Dot materials

A

TEM, Absorption Spectroscopy, Line broadening using X-ray diffraction

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9
Q

Actual particles can deviate from the Stokes model for sedimentation if they are:

A

Asymmetrical, solvated

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10
Q

Uses for surfactants

A

Stabilization of thin films
Formation of emulsions
Lubrication

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