Q. 3.55 - An Introduction to General, Organic, and Biological Chemistry

Question

A patient arrives in the emergency room with a burn caused by steam, Calculate the heat, in kilocalories, that is released when $18.0 g$ of steam at ${100}^{\circ }C$ hits the skin, condenses, and cools to body temperature of $37.0^{\circ }C$.

Step-by-Step Solution

Answer

The heat energy in Kilocalories when it released $18 g$ of steam at ${100}^{\circ }C$ and cools to body temperature of $37.0^{\circ }C$ is $10.9 Kcal$

Step1: Given information.

The Information are given as follows:

Mass of steam$=18.0 g$

Initial temperature$={100}^{\circ }C$

Cool to body temperature$={37}^{\circ }C$

Step2: Find the Heat Change.

The total energy is equal to the sum of the energy released during steam condensation and the energy required to chill the liquid.

Steam's mass is $18.0 g$

Heat of Vaporization is $540 cal/g$

Calculate the amount of energy released when $18.0 g$ of steam is condensed as follows:

$$\begin{gathered} Heat change=mass\times heat of vaporization \\ =18.0\times 540 cal/g \\ =9720 cal \end{gathered}$$

Step3: Calculate the Energy released.

Calculate the energy released during the cooling of the liquid from ${100}^{\circ }C$ to ${37}^{\circ }C$ using the following formula:

$$\begin{gathered} Heat=mass\times temperature change\times specific heat \\ =18.0 g\times \left({100}^{\circ }C-37.0^{\circ }C\right)\times 1 cal/g^{\circ }C \\ =1130 cal \end{gathered}$$

Step4: Find the Total Heat Energy.

$$\begin{gathered} Total Heat energy=9720 cal+1130 cal \\ =10850 cal\times \frac{1 Kcal}{1000 cal} \\ =10.9 Kcal \end{gathered}$$

The Total Heat released is $10.9 Kcal$