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matse exam 2 | Questions Solved 100% Correct| Verified Answers
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matse exam 2 | Questions Solved 100% Correct| Verified Answers
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matse exam 2 | Questions Solved 100% Correct|Verified Answers
Which is true regarding dislocations in crystals?
A) they are categorized as being two-dimensional defects
B) they occur only in metals
C) they can be described quantitatively by their Burger's vector
D) cannot be readily detected because they are too small. - ✔✔C) they can be described
quantitatively by their Burger's vector
Twin boundaries, grain boundaries, and stacking faults all represent which kind of defect?
A) Types of dislocations
B) Two dimensional defects
C) Linear defects
D) Point defects - ✔✔B) Two dimensional defects
Which of the following statements describes Fick's first law?
A) the diffusivity is proportional to the concentration gradient
B) the net mass flux is proportional to the diffusivity
C) the flux is described by the error function
D) the diffusivity is thermally activated - ✔✔A) the diffusivity is proportional to the
concentration gradient
Diffusion in a solid
A) is facilitated by point defects such as vacancies
B) is a function of temperature
C) requires a concentration gradient,
D) all of the above - ✔✔D) all of the above
,A condition of non-steady state diffusion (i.e. the net flux is varying with time) can be described
by
A) Fick's Second law
B) the Avrami equation
C) an Arrhenius relationship
D) none of the above - ✔✔A) Fick's Second law
Diffusivity has units of
A) mass/time2
B) length2/time
C) mass/length2•time
D) mass-length/time - ✔✔B) length2/time
Which of the following statements about diffusion is TRUE?
A) As the bond strength is increased, the diffusion coefficient increases
B) The smaller the diffusing species the smaller the diffusivity
C) As atomic packing factor increases, diffusivity increases
D) As bond energy increases, the activation energy for diffusion increases - ✔✔D) As bond
energy increases, the activation energy for diffusion increases
Ethane (CH3CH3) and Fluoromethane (CH3F) have the same number of electrons and are
essentially the same size. However, ethane has a boiling point of 184.5C and fluoromethane has
a boiling point of 194.7C. Which answer best explains this 10 degree difference in boiling point
in terms of the van der Waals forces present.
A) It has nothing to do with van der Waals
B) Both molecules have both dispersion and orientation forces present, but fluoromethane is a
slightly larger molecule
, C) Both molecules have dispersion forces, but fluoromethane also has orientation forces
present
D) Both molecules are non-polar, but fluoromethane is a slightly larger molecule - ✔✔C)
Both molecules have dispersion forces, but fluoromethane also has orientation forces present
Covalent interactions are generally long range (i.e., greater than 10 nm).
True
False - ✔✔False
Hydrogen bonding is predominately found between polar molecules.
True
False - ✔✔True
Describe all types of bonding that you would expect to exist in each of the following
compounds: a silicon carbide crystal
A) Predominantly covalent and some ionic
B) Predominantly ionic and some covalent
C) Equally ionic and covalent
D) Ionic only - ✔✔A) Predominantly covalent and some ionic
Describe all types of bonding that you would expect to exist in each of the following
compounds: potassium fluoride (KF)
A) predominantly covalent and some ionic
B) ionic only
C) covalent only
D) predominantly ionic and some covalent - ✔✔D) predominantly ionic and some covalent
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