Chapter 15, Problem 126A

Interpretation Introduction

Interpretation:

The final temperature of water needs to be calculated.

Concept introduction:

The amount of heat obtained from burning oil can be calculated by its specific energy.

Answer to Problem 126A

The final temperature of the water will be 91.11°C.

Explanation of Solution

1kg of soy oil gives 39.2 MJ energy.

Energy provided by 12.2g soy oil:

$\begin{array}{l}E=\frac{39.2\times 12.2}{1000}\\ E=0.478MJ=4.78\times {10}^{5}J\end{array}$

This energy is equal to heat provided,

$Q=E=4.78\times {10}^{5}J$

By first law of thermodynamics,

$Q=mC\Delta T$

Mass of water m = 1.6 kg

Specific heat of waterC = 4200 J/kg°C

$\begin{array}{l}\Delta T=\frac{Q}{mC}\\ \Delta T=\frac{4.78\times {10}^5}{1.6\times 4.2\times {10}^3}\\ \Delta T=71.11°C\end{array}$

$FinaltemperatureT=20+71.11=91.11°C$

Conclusion

The heat of soy oil was calculated from its specific energy and from it the final temperature of water was calculated.