I have a table that has the vapor pressure of water at selected temperatures. It is converted from celsius to torr. For example:
18°C = 15.5 torr
19°C = 16.5 torr
Unfortunately, the temperature I got is 18.5°C. How do I convert it to torr? The book has no equation and I can't find it anyhwere.
The best thing to do is to interpolate.
You want 18.5 which is half way between 18 and 19. So take half way between 15.5 and 16.5. For small differences like this there is little error involved.
To convert the temperature of 18.5°C to torr using interpolation, you can follow these steps:
1. Identify the two known temperatures in your table that are closest to the desired temperature of 18.5°C. In this case, the nearest temperatures are 18°C and 19°C.
2. Find the corresponding vapor pressure values for the two known temperatures. From your example, the vapor pressures are 15.5 torr for 18°C and 16.5 torr for 19°C.
3. Calculate the difference between the two vapor pressure values: 16.5 torr - 15.5 torr = 1 torr.
4. Divide this difference in vapor pressure by the difference in temperature between the two known temperatures: 1 torr / (19°C - 18°C) = 1 torr / 1°C = 1 torr/°C.
5. Multiply this temperature coefficient (1 torr/°C) by the difference between the desired temperature (18.5°C) and the lower known temperature (18°C): (18.5°C - 18°C) * 1 torr/°C = 0.5 torr.
6. Add this calculated value to the vapor pressure at the lower known temperature: 15.5 torr + 0.5 torr = 16 torr (rounded to the nearest tenth).
Therefore, the estimated vapor pressure of water at 18.5°C using interpolation is approximately 16 torr.