Homework 8 I. Determine the number of degrees of freedom for the following syste
ID: 702622 • Letter: H
Question
Homework 8 I. Determine the number of degrees of freedom for the following systems a) b) c) The ratio of the mass of chlorobenzene to that of water collected in a steam distillation is 1.93 when the mixture was boiled at 343.85 K and 56.434 kPa. If the vapor pressure of water at this temperature is 43.102 kPa, calculate the molar mass of chlorobenzene. (25 points) Under atmospheric pressure 1 kg of pure naphthalene is to be prepared by steam distillation at 372.4 K. What mass of steam is required to perform this purification? The vapor pressure of pure water at 372.4 K is 98.805 kPa. (25 points) A solution of sodium chloride in water at the equilibrium pressure A solution of potassium chloride and sodium chloride at 298 K at latm pressure Ice in a solution of water and alcohol. (25 points) 2. 3. 4. The aluminum-selenium system was determined from thermal analysis. Al Ses melts 50 °C and forms a cutectic both with aluminum and with congruently at approximately 9 selenium at a very low concentration of the alloying element and at a temperature close to the melting point if the base element. Draw a diagram from this information and give the composition of the phases. Aluminum melts at 659.7 °C and selenium melts at approximately 217 °C. (25 points)Explanation / Answer
Ans 1
Degree of freedom F = C - P + 2
C = number of components
P = number of phases present
Part a
Solution of NaCl in water gives two ions (Na+ & Cl-)
P = 1
C = 2
F = 2 - 1 + 2 = 3
Now given that equilibrium pressure is a specified condition
F = 3 - 1 = 2
Part b
3 ions present
K+ , Na+ & Cl-
C = 3
P = 1
F = 3 - 1 +2 = 4
Conditions of constant temperature and constant pressure
F = 4 - 1 = 3
Part C
Ice and water is one component
C = 2
P = 2 ( solid and liquid phase)
F = 2 - 2 +2
= 2
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