Ideal Gas Law Calculator - PV = nRT
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Step-by-Step Solution
Ideal Gas Law Calculator
Use this calculator to find the missing pressure, volume, temperature, or amount of gas from the ideal gas equation PV = nRT. It is built for chemistry practice, homework checking, classroom examples, and quick verification of gas-law calculations.
A major advantage of this calculator is its unit handling. You can enter temperature in K, °C, or °F; pressure in Pa, kPa, atm, bar, or mmHg; and volume in m³, L, or mL. The calculator converts the values to compatible internal units before solving and then displays the answer in the selected unit.
What Can You Calculate?
- Temperature: T = PV / nR
- Pressure: P = nRT / V
- Moles of gas: n = PV / RT
- Volume: V = nRT / P
How to Use This Calculator
- Choose the quantity you want to calculate.
- Enter the other three known quantities.
- Select the correct unit beside temperature, pressure, and volume.
- Select Calculate to get the answer.
- Select Step-by-step Solution to review the equation, conversions, substitution, and final result.
Ideal Gas Law Formula
The ideal gas law connects four quantities that describe a gas: pressure, volume, amount of gas, and absolute temperature.
This calculator uses R = 8.314462618 J/(mol·K). Because this value is used with SI-compatible quantities, entered pressure and volume are converted internally before the calculation is performed.
Temperature and the Ideal Gas Law
Temperature must be treated as an absolute temperature in the gas equation. If you enter Celsius or Fahrenheit, the calculator first converts it to kelvin. For example, 0 °C corresponds to 273.15 K, so 0 °C should not be inserted directly as T in PV = nRT.
Pressure and Volume Units
Pressure may be entered as Pa, kPa, atm, bar, or mmHg. Volume may be entered as m³, L, or mL. Keeping the units consistent is essential because the numerical value of a gas-law result depends on the units used in the equation.
Worked Example: Calculate Pressure
Consider 0.50 mol of gas at 300 K occupying 10 L. To calculate pressure, rearrange the equation:
The calculator converts 10 L to 0.010 m³, applies the selected value of R, and returns the pressure in the pressure unit selected by the user. The step-by-step output also shows the converted quantities used in the calculation.
Common Mistakes to Avoid
- Using °C directly instead of converting temperature to kelvin.
- Mixing litres and cubic metres without conversion.
- Combining pressure values expressed in different units.
- Using the wrong rearrangement of PV = nRT.
- Entering zero or negative values for a gas quantity.
Ideal Gas Law Calculator FAQs
What is PV = nRT?
PV = nRT is the ideal gas law. It relates pressure (P), volume (V), amount of gas in moles (n), the gas constant (R), and absolute temperature (T).
What value of R is used?
The calculator uses R = 8.314462618 J/(mol·K) and converts the entered values to compatible internal units before calculation.
Can I use Celsius or Fahrenheit?
Yes. Select °C or °F from the temperature unit menu. The calculator converts the entered temperature to kelvin for the calculation and converts a calculated temperature back to the selected unit.
Can I enter pressure in atm?
Yes. You can use atm, Pa, kPa, bar, or mmHg. The selected pressure unit is also used when pressure is the calculated quantity.
Can I enter volume in litres?
Yes. The volume menu supports L, mL, and m³. The calculator handles the conversion before applying PV = nRT.
How do I calculate moles?
Select Moles of Gas and enter pressure, temperature, and volume. The calculator uses n = PV / RT and reports the amount in mol.
How do I calculate gas volume?
Select Volume and enter pressure, temperature, and moles. The calculator uses V = nRT / P and displays the answer in the selected volume unit.
Study tip: Write PV = nRT first, identify the unknown, convert units, substitute the values, and check that the final unit matches the quantity you calculated.