Question

Explain the decrease in volume of 8.1% as iron undergoes a phase transition from a BCC structure to an FCC structure at 912 °C

Answer #1

Explain why BCC metals undergo a brittle to ductile
transition and fcc metals do not in terms of dislocations and the
metals' crystal structures ?
Please explain in a good words!!! Thanks

(i) The element, S (sulfur), undergoes a phase transition from a
rhombic form to a monoclinic form at 95.4°C. If ΔHtransition=0.38
kJ mol-1, calculate ΔStransition under the above conditions. Show
all working. (ii) Monoclinic sulfur is known to melt at 119°C.
Given ΔHfusion=1.23 kJ mol-1, calculate, showing all working,
ΔSfusion. (iii) Given the S occurs as S8 in solid or liquid forms,
convert the values of the enthalpy and entropy of fusion above to
those expected for S8.

Iron undergoes two solid-solid transitions as it is heated from
298 K to 1800 K. Given delta Ho = 0.900 kJ
mol-1 at 1184 K for the a - g transition delta
Ho = 0.837 kJ mol-1 at 1665 K for a g - d
transition, calculate delta Sosystem for each
change. Comment on the changes in randomness

Calculate the wavelength of the photon emitted when the hydrogen
atom undergoes a transition from n=8 to n=4.
(R=1.096776x10^7m-1)
Please explain hwo you got the answer

As it cools down from an elevated temperature, pure iron is
known to undergo an allotropic transformation at 912°C.
Why does this come with an observed volume change in the
material? Will this volume change be larger or smaller than that
seen in a 0.5wt% carbon steel?

An electron in He+ undergoes a transition from n = 4 to n = 2
state. Calculate the (a) energy in J, (b) frequency in Hz, (c)
wavelength in nm and (d) wave number in cm-1 of the photon
emitted.

True ? False?
• The temperature of a phase transition generally depends on
pressure.
• There are no conditions at which a two-component system will have
4 of its phases in equilibrium with each other.
• When nA molesofaliquidsubstancewithpartialmolarvolume ¯ VA
isaddedtoalargeamount of solvent the total volume of the mixture is
generally increased by ∆V = nA ¯ VA.
•
Thechemicalpotentialsofthecomponentsinamixturedefinehowtheinternalenergychanges
upon changing the composition of the system at constant volume and
entropy.
• The change in entropy of a...

Suppose 4.00 mol of an ideal gas undergoes a reversible
isothermal expansion from volume V1 to volume V2 = 8V1 at
temperature T = 300 K. Find (a) the work done by the gas and (b)
the entropy change of the gas. (c) If the expansion is reversible
and adiabatic instead of isothermal, what is the entropy change of
the gas?

1. The following data were obtained from a Charpy impact test
for a ductile cast iron containing 2.55 wt% Si. Plot the data and
find the ductile to brittle transition temperature. What does this
transition temperature signify? Would you use this material in a
product that undergoes constant impact forces below 0oC?
Why or why not? Explain. Use graph supplied on next page.
TEST TEMPERATURE (oC)
IMPACT ENERGY (ft-lb)
-50
4
-20
4
0
6.4
8
8.8
14
12
20...

1 mole of a gas undergoes a mechanically reversible isothermal
expansion from an initial volume 1 liter to a final volume 10 liter
at 25oC. In the process, 2.3 kJ of heat is absorbed in the system
from the surrounding. The gas follows the following formula:
V=RTP+b where V is the molar specific volume, and Tand Pare
temperature (abosolute) and gas pressure respectively. Given R=
8.314 J/(mol.K) and b= 0.0005 m3. Evaluate the following a) Work
(include sign) b) Change...

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