TeXes Science Practice Test

After heating 5 grams of glacial acetic acid at 98°C with 2500 joules of energy, what state will the substance be in?

1. Liquid at 98°C

2. Solid at room temperature

3. Five grams of acetic acid vapor at a temperature above 118°C

4. Mixture of liquid and vapor

The correct answer is: Five grams of acetic acid vapor at a temperature above 118°C

To determine the state of glacial acetic acid after heating it with 2500 joules of energy, it is important to understand the properties of the substance and the phase transitions it can undergo. Glacial acetic acid is typically in a liquid state at room temperature and has a boiling point of approximately 118°C. When you heat it to 98°C, it remains in a liquid state, as that temperature is below its boiling point. However, by adding 2500 joules of energy, which corresponds to a significant amount of heat, the temperature of the acetic acid can be raised significantly. The key here is that the additional energy provided (2500 joules) is sufficient to not only reach the boiling point but also to combine with the heat needed for phase transition from liquid to vapor. Upon reaching the boiling point at 118°C, the acetic acid begins to evaporate, which means it changes from a liquid to a vapor. If the acetic acid is heated in a closed system and 2500 joules of energy exceeds the heat necessary for the phase change, it suggests that the acetic acid will transition completely to the vapor state, and thus will exist as a vapor at a temperature above 118