Final answer:
The water absorption at 50% relative humidity of poly(vinyl pyrrolidone) at 25 °C cannot be determined from the given information.
Step-by-step explanation:
The water absorption at 50% relative humidity of poly(vinyl pyrrolidone) can be found by using the Polymers Database. However, the provided information does not include the water absorption data for poly(vinyl pyrrolidone) at 25 °C and 50% relative humidity. Therefore, the specific water absorption value you are looking for cannot be determined from the given information.