For a laboratory investigation some students put a strip of shiny metal into a beaker of blue solution and then stored the beake
r on a shelf
overnight. The next morning, the students recorded observations about the metal and the solution in the box below.
Students' Observations
Exhibit
. The solution is lighter in color,
The volume of solution is the same.
• The metal strip is shiny above the surface of the solution
• The metal strip is not shiny below the surface of the solution.
• The metal strip below the surface of the solution has a dark
coat of flaky material
• When the metal strip is touched, the flaky material falls off.
Based on their observations, can the students correctly conclude that a chemical reaction occurred?
A. No, because the metal strip was still visible
B. Yes, because a new material of a different color formed on part of the metal strip
c. No, because the solution stayed blue
ble solution stayed the same
12 AM
overnight. The next morning, the students recorded observations about the metal and the solution in the box below.
Students' Observations
Exhibit
. The solution is lighter in color,
The volume of solution is the same.
• The metal strip is shiny above the surface of the solution
• The metal strip is not shiny below the surface of the solution.
• The metal strip below the surface of the solution has a dark
coat of flaky material
• When the metal strip is touched, the flaky material falls off.
Based on their observations, can the students correctly conclude that a chemical reaction occurred?
A. No, because the metal strip was still visible
B. Yes, because a new material of a different color formed on part of the metal strip
c. No, because the solution stayed blue
ble solution stayed the same
12 AM
1 answer:
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This problem is describing a gas mixture whose mole fraction of hexane in nitrogen is 0.58 and which is being fed to a condenser at 75 °C and 3.0 atm, obtaining a product at 3.0 atm and 20 °C, so that the removed heat from the system is required.
In this case, it is recommended to write the enthalpy for each substance as follows:
Whereas the specific heat of liquid and gaseous n-hexane are about 200 J/(mol*K) and 160 J/(mol*K) respectively, its condensation enthalpy is 31.5 kJ/mol, boiling point is 69 °C and the specific heat of gaseous nitrogen is about 29.1 J/(mol*K) according to the NIST data tables and and
are the mole fractions in the gaseous mixture. Next, we proceed to the calculation of both heat terms as shown below:
It is seen that the heat released by the nitrogen is neglectable in comparison to n-hexanes, however, a rigorous calculation is being presented. Then, we add the previously calculated enthalpies to compute the amount of heat that is removed by the condenser:
Finally we convert this result to kJ:
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