Zinc is often used to calibrate calorimeters because it undergoes a very sharp phase transition from the solid to the liquid at 419.5°C. Calculate the enthalpy change when 5 g of zinc metal is heated from 100°C to the point where the entire sample is melted. (The heat of fusion for zinc is 112.4 J/g and its specific heat capacity is 0.388 J/g°C.)
q1 = mass Zn x specific heat Zn x (Tf - Ti) where Tf is final T (419.5) and Ti is initial T (100).
q2 = mass Zn x heat of fusion
total = q1 + q2.
Well, I guess zinc is a bit of a drama queen with that sharp phase transition! But hey, let's calculate its enthalpy change, shall we?
First, we need to calculate the heat required to raise the temperature of the zinc from 100°C to its melting point. We can use the specific heat capacity to do that. The formula to calculate heat is Q = m * c * ΔT, where Q is the heat, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
Q = (5 g) * (0.388 J/g°C) * (419.5°C - 100°C)
Q = 5 * 0.388 * 319.5 = 615.733 J
So, the heat required to raise the temperature to the melting point is 615.733 J.
Now, we need to calculate the heat required to melt the zinc. To do that, we use the heat of fusion, which is 112.4 J/g.
Q = (5 g) * (112.4 J/g)
Q = 562 J
So, the heat required to melt the zinc is 562 J.
Lastly, we add the two heats together to get the total enthalpy change:
Total enthalpy change = 615.733 J + 562 J
Total enthalpy change = 1177.733 J
Therefore, the enthalpy change when 5 g of zinc metal is heated from 100°C to the point where the entire sample is melted is 1177.733 J. Hope that brings a little heat to your day!
To calculate the enthalpy change, we need to consider two steps: heating the zinc from 100°C to its melting point, and then melting the entire sample.
Step 1: Heating from 100°C to the melting point:
First, we need to calculate the heat required to raise the temperature of the zinc from 100°C to its melting point. We use the formula:
Q = m * c * ΔT
Where:
Q is the heat energy (enthalpy change)
m is the mass of the zinc (5 g)
c is the specific heat capacity of zinc (0.388 J/g°C)
ΔT is the change in temperature (melting point - initial temperature)
Given:
Initial temperature = 100°C
Melting point = 419.5°C
ΔT = 419.5°C - 100°C = 319.5°C
Plugging in the values:
Q = 5 g * 0.388 J/g°C * 319.5°C
Q = 607.14 J
Therefore, the heat required to raise the temperature of the zinc to its melting point is 607.14 J.
Step 2: Melting the entire sample:
Next, we need to calculate the heat required to melt the entire sample of zinc. We use the formula:
Q = m * ΔH_fus
Where:
Q is the heat energy (enthalpy change)
m is the mass of the zinc (5 g)
ΔH_fus is the heat of fusion for zinc (112.4 J/g)
Plugging in the values:
Q = 5 g * 112.4 J/g
Q = 562 J
Therefore, the heat required to melt the entire sample of zinc is 562 J.
Finally, we add the heat from both steps to get the total enthalpy change:
Total enthalpy change = Q1 + Q2
Total enthalpy change = 607.14 J + 562 J
Total enthalpy change = 1169.14 J
Therefore, the enthalpy change when 5 g of zinc metal is heated from 100°C to the point where the entire sample is melted is 1169.14 J.
To calculate the enthalpy change when heating zinc, we need to consider two steps: heating the solid zinc from 100°C to its melting point (419.5°C), and then melting the entire sample.
First, let's calculate the heat required to raise the temperature of the solid zinc from 100°C to its melting point:
Q1 = m * c * ΔT1
Where:
Q1 is the heat energy absorbed or released
m is the mass of the substance (5 g)
c is the specific heat capacity of zinc (0.388 J/g°C)
ΔT1 is the change in temperature (419.5°C - 100°C)
Q1 = (5 g) * (0.388 J/g°C) * (419.5°C - 100°C)
Q1 = 5 g * 0.388 J/g°C * 319.5°C
Q1 = 619.62 J
Next, let's calculate the heat required to melt the entire sample:
Q2 = m * ΔHf
Where:
Q2 is the heat energy absorbed or released during melting
m is the mass of the substance (5 g)
ΔHf is the heat of fusion for zinc (112.4 J/g)
Q2 = (5 g) * (112.4 J/g)
Q2 = 562 J
The total enthalpy change (ΔH) is the sum of Q1 and Q2:
ΔH = Q1 + Q2
ΔH = 619.62 J + 562 J
ΔH = 1181.62 J
Therefore, the enthalpy change when 5 g of zinc metal is heated from 100°C to the point where the entire sample is melted is 1181.62 J.