Question

32 thermodynamics
a chemical reaction absorbs 200 j of heat and causes the system to expand. if δe = 50 j, what is the work for this process?
150 j
250 j
-250 j
-150 j

Explanation:

Step1: Recall the first law of thermodynamics

The first law of thermodynamics is given by the equation $\Delta E = q + w$, where $\Delta E$ is the change in internal energy, $q$ is the heat added to the system, and $w$ is the work done on the system. When the system absorbs heat, $q$ is positive, so $q = 200\space J$. When the system expands, it does work on the surroundings, so the work done on the system $w$ will be negative (by convention). We know $\Delta E = 50\space J$.

Step2: Rearrange the formula to solve for $w$

From $\Delta E = q + w$, we can rearrange it to $w=\Delta E - q$.

Step3: Substitute the known values

Substitute $\Delta E = 50\space J$ and $q = 200\space J$ into the formula: $w = 50 - 200=- 150\space J$.

Answer:

-150 J