How many kcal of heat energy are required or released when 1.73 moles of butanol , C4H9OH, is warmed from -175.8 degrees F to 360.9 degrees F? The following information concerning butanol applies:
normal melting point: 12.5 degrees C
normal boiling point: 162.8 degrees C
Cp (s) = 2.91 J/g degrees C
Cp (l) = 3.27 J/g degrees C
Cp (g) = 2.36 J/g degrees C
Show the diagram that applies to this substance, including mp, bp, delta Hc, delta Hv, phases involved, starting point and stopping point.
Then calculate the heats needed for for each step and the final heat required or released. State whether required or released in answer.
Ok, I know how to do the staircase diagram with the phases at each level, but I'm not sure how to calculate the heat needed for each step.
when it is solid, liquid, or gas, the heat involved is m*c*deltaTemp
At the transition pointss, melting, and again at boiling, there is a heat
L*mass where L, the latent heat per mass, is either Lv (vaporiation heat/gram) or Lf(melting heat/gram)
We will be happy to critique your work.
To calculate the heat needed for each step in the process of warming the butanol, we need to consider the changes in temperature and phase transitions. Let's break down the process step by step:
Step 1: Heating from -175.8 degrees F to the melting point
To calculate the heat required for this step, we first need to convert -175.8 degrees F to degrees Celsius. The formula to convert Fahrenheit to Celsius is: °C = (°F - 32) * 5/9.
So, -175.8 degrees F = (-175.8 - 32) * 5/9 = -115.44 degrees C.
Since butanol is in a solid state below its melting point, we will have a phase transition from solid to liquid. To calculate the heat required for this phase transition, we use the formula:
Q1 = moles of substance * deltaHf
where deltaHf is the heat of fusion (or heat of melting) for the substance. For butanol, let's assume the heat of fusion is given or can be looked up.
Step 2: Heating from the melting point to the boiling point
The melting point of butanol is given as 12.5 degrees C. We need to calculate the heat required to raise the temperature from the melting point to the boiling point.
First, convert 12.5 degrees C to Fahrenheit using the formula: °F = °C * 9/5 + 32.
12.5 degrees C = 12.5 * 9/5 + 32 = 54.5 degrees F.
We need to calculate the heat required for this temperature range using the formula:
Q2 = moles of substance * Cp (l) * change in temperature
where Cp (l) is the specific heat capacity of the liquid phase. For butanol, the specific heat capacity in the liquid phase is given as 3.27 J/g°C.
Step 3: Heating from the boiling point to the final temperature
The boiling point of butanol is given as 162.8 degrees C. We need to calculate the heat required to raise the temperature from the boiling point to the final temperature.
First, convert 360.9 degrees F to Celsius using the formula: °C = (°F - 32) * 5/9.
360.9 degrees F = (360.9 - 32) * 5/9 = 183.8 degrees C.
We need to calculate the heat required for this temperature range using the same formula as in Step 2, using the specific heat capacity of the gaseous phase (Cp (g)).
Step 4: Calculate the total heat required or released
To find the total heat, add up the heats required for each step:
Total heat = Q1 + Q2 + Q3
Note that if any phase transitions occur, the heat for those specific transitions needs to be included.
If you have the values for deltaHf and the specific heat capacities (Cp) of the different phases, you can calculate the heats needed for each step and determine whether heat is required or released based on the signs of the values.