How to use the gas collected over water calculator
Correct the volume of a gas collected over water to find the dry gas pressure and moles. Enter total gas pressure, water temperature, gas volume collected in the fields above; the vapor pressure of water, dry gas pressure, moles of dry gas are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “gas over water correction”, “dry gas pressure”, “moles of gas collected over water”, “calculate gas collected over water”, “find vapor pressure of water”.
Formula
Variables
- Pt — Total gas pressure (kPa)
- T — Water temperature (°C)
- V — Gas volume collected (mL)
Worked example
With total gas pressure = 101.3 kPa, water temperature = 25 °C, gas volume collected = 50 mL, the calculator gives vapor pressure of water ≈ 3.167778 kPa; dry gas pressure ≈ 98.13222 kPa; moles of dry gas ≈ 1.979305 mmol.
Frequently asked questions
What is the gas collected over water calculator used for?
Correct the volume of a gas collected over water to find the dry gas pressure and moles. It helps with questions such as “gas over water correction”, “dry gas pressure”, “moles of gas collected over water”.
What is the formula for the gas collected over water calculation?
Vapor pressure of water (kPa) = 0.6108 × exp(17.27 × T / (T+237.3)). Dry gas pressure (kPa) = Pt-[Vapor pressure of water]. Moles of dry gas (mmol) = [Dry gas pressure] × V / (RGAS × (T+273.15)). Here Pt is total gas pressure (kPa), T is water temperature (°C), V is gas volume collected (mL).
What inputs do I need for the gas collected over water calculator?
You need total gas pressure in kPa, water temperature in °C, gas volume collected in mL. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the gas collected over water calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the gas collected over water result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.