CHE 132 Lecture Notes - Lecture 3: Standard Molar Entropy, Endothermic Process

• School: Stony Brook University
• Department: Chemistry
• Course: CHE 132
• Professor: Elizabeth Boon

Document Summary

The sign of entropy change can be predicted based on general trends. The conversion of gas into liquid will result in a decrease in the freedom of movement. The decrease in the freedom of movement will result in a negative entropy. Ex: 2c8h12 (l) + 25o2 (g) 16co2 (g) + 18h2o (g: this will result in entropy being positive because 2 moles of liquid + 25 moles of gas results in 34 moles of gas. Gas have greater freedom of movement so entropy increases. We can use the tabulated standard molar entropy values to calculate the overall entropy change for a reaction under standard conditions, similar to when calculating the enthalpy change. The entropy change of this problem equals -290. If the entropy change of the system is negative, then the entropy change of the surrounding has to be a larger positive value for the entropy of the universe to be > 0.