(a) How many kilograms are there in 1.00 mole of iron? kg/mol (b) Starting with
ID: 2135979 • Letter: #
Question
(a) How many kilograms are there in 1.00 mole of iron?kg/mol
(b) Starting with the density of iron and the result of part (a), compute the molar density of iron (the number of moles of iron per cubic meter).
mol/m3
(c) Calculate the number density of iron atoms using Avogadro's number.
atoms/m3
(d) Obtain the number density of conduction electrons given that there are two conduction electrons per iron atom.
electrons/m3
(e) Calculate the drift speed of conduction electrons in this wire.
m/s Plethysmographs are devices used for measuring changes in the volume of internal organs or limbs. In one form of this device, a rubber capillary tube with an inside diameter of 1.10 mm is filled with mercury at 20 degree C. The resistance of the mercury is measured with the aid of electrodes sealed into the ends of the tube. If 100 cm of the tube is wound in a helix around a patient's upper arm, the blood flow during a heartbeat causes the arm to expand, stretching the length of the tube by 0.044 0 cm. From this observation and assuming cylindrical symmetry, you can find the change in volume of the arm, which gives an indication of blood flow. Take the resistivity of mercury to be 9.58 Times 10-7 ? · m. (Hint: The fraction by which the cross-sectional area of the mercury column decreases is the fraction by which the length increases because the volume of mercury is constant. ) Calculate the resistance of the mercury. Calculate the fractional change in resistance during the heartbeat.
Explanation / Answer
a)
M=55.85 g/mol =0.05585 Kg/mol
b)
Molar density =p/M =7860/0.05585 =1.41*10^3 mol/m^3
c)
N=(6.02*10^23)*(1.41*10^5) =8.49*10^28 atoms/m^3
d)
n=2*8.49*10^28 =1.7*10^29 electrons/m^3
e)
V=I/nAq =33/(1.7*10^29*9.5*10^-6*1.6*10^-19)
V=1.28*10^-4 m/s
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