# Physics. Urgent help!!

posted by
**Papito**
.

The relative humidity is 55% on a day when the temperature is 30.0°C. Using the graph below, determine the number of moles of water vapor per cubic meter of air.

on the graph, Vapor pressure of water is on the y-axis and temperature on the x-axis 30C cordinates with 4200 Pa of water vapor.

This how i tried to sove it.

Since 30 corresponds to 4200 Pa

T in Kelvin =303

n/v = p/RT

=4200/(8.32 x 303)

= 1.67

the answer is wrong

You read the vapor pressure of water vs temp on the graph. Then you put that in the pvnrt equation. What makes you think that was the partial pressure of the water in the air on that day? If the air had been saturated with water, yes, but this was at 55 percent humidity.

Thank you.