Some thermodynamic properties of ethanol are listed in the table.

Thermodynamic Properties
\begin{tabular}{|l|c|}
\hline Property & Value \\
\hline (solid) & [tex]$0.5 \, \text{J/g} \, ^{\circ} \text{C}$[/tex] \\
\hline (liquid) & [tex]$1.0 \, \text{J/g} \, ^{\circ} \text{C}$[/tex] \\
\hline (gas) & [tex]$2.0 \, \text{J/g} \, ^{\circ} \text{C}$[/tex] \\
\hline Melting Point & [tex]$-114^{\circ} \text{C}$[/tex] \\
\hline Boiling Point & [tex]$78^{\circ} \text{C}$[/tex] \\
\hline
\end{tabular}

How much heat is released when 40.0 g of ethanol cools from [tex]$-120^{\circ} \text{C}$[/tex] to [tex]$-136^{\circ} \text{C}$[/tex]?

A. 640 J
B. 580 J
C. 320 J
D. 290 J



Answer :

To find out how much heat is released when 40.0 grams of ethanol cools from [tex]\(-120^{\circ}C\)[/tex] to [tex]\(-136^{\circ}C\)[/tex], we follow these steps:

1. Identify the given data:
- Mass of ethanol ([tex]\(m\)[/tex]): 40.0 grams
- Initial temperature ([tex]\(T_i\)[/tex]): [tex]\(-120^{\circ}C\)[/tex]
- Final temperature ([tex]\(T_f\)[/tex]): [tex]\(-136^{\circ}C\)[/tex]
- Specific heat capacity in the solid state ([tex]\(c\)[/tex]): [tex]\(0.5 \, J/g^{\circ}C\)[/tex]

2. Calculate the temperature difference ([tex]\(\Delta T\)[/tex]):
[tex]\[ \Delta T = T_i - T_f = (-120^{\circ}C) - (-136^{\circ}C) = -120 + 136 = 16^{\circ}C \][/tex]

3. Calculate the heat released ([tex]\(q\)[/tex]) using the formula:
[tex]\[ q = m \times c \times \Delta T \][/tex]
Substituting the values:
[tex]\[ q = 40.0 \, g \times 0.5 \, J/g^{\circ}C \times 16^{\circ}C \][/tex]

4. Perform the multiplication to find [tex]\(q\)[/tex]:
[tex]\[ q = 40.0 \times 0.5 \times 16 = 320.0 \, J \][/tex]

Therefore, the amount of heat released when 40.0 grams of ethanol cools from [tex]\(-120^{\circ}C\)[/tex] to [tex]\(-136^{\circ}C\)[/tex] is 320 J.

So, the correct answer is:
[tex]\[ \boxed{320 \, J} \][/tex]