Example 1 — Find Final Pressure
\(P_1=1.00\ \mathrm{atm}, V_1=2.50\ \mathrm{L}, T_1=300\ \mathrm{K}; V_2=3.10\ \mathrm{L}, T_2=350\ \mathrm{K}\).
Combined Gas Law Calculator
Combined Gas Law Calculator solves P1V1/T1 = P2V2/T2, handles unit conversions, Kelvin temperatures, quick scenarios, step-by-step equation previews for students.
Choose the unknown variable; enter the other five values.
Equation Preview
P₁V₁/T₁ = P₂V₂/T₂
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Helping Notes
- Use absolute temperature (Kelvin). °C/°F entries are converted to K for the law to hold. :contentReference[oaicite:1]{index=1}
- Typical pressure units: atm, kPa, Pa, bar, mmHg, psi (interconvertible). :contentReference[oaicite:2]{index=2}
- Combined gas law: \( \frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2} \). Enter five values and solve the sixth. :contentReference[oaicite:3]{index=3}
Results
Primary Result
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Rearranged Formula & Steps
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Equality Check (numeric)
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What Is a Combined Gas Law Calculator?
A Combined Gas Law Calculator computes any one unknown variable in the relationship between pressure \(P\), volume \(V\), and absolute temperature \(T\) for a fixed amount of gas:
By providing the other five values, users can quickly find the final pressure, volume, or temperature. The model assumes constant moles and ideal gas behavior. Using absolute temperatures (Kelvin) and consistent units ensures accurate results for classroom exercises, lab experiments, or real-world estimates like tank refills or temperature-driven pressure changes.About the Combined Gas Law Calculator
The combined gas law merges Boyle’s Law (\(PV=\text{const}\) at constant \(T\)), Charles’s Law (\(V/T=\text{const}\) at constant \(P\)), and Gay-Lussac’s Law (\(P/T=\text{const}\) at constant \(V\)) into one equation for two states of the same gas sample.
The calculator emphasizes unit consistency: pressure (atm, bar, kPa, mmHg), volume (L, mL), and absolute temperature (K). Celsius or Fahrenheit inputs are converted automatically:
Assumptions include no phase change, constant moles, and ideal gas behavior. For extreme pressures or very low temperatures, non-ideal corrections (e.g., van der Waals) may be necessary.
How to Use the Combined Gas Law Calculator
- Enter any five of the six variables \(P_1,V_1,T_1,P_2,V_2,T_2\). Ensure consistent pressure and volume units across states.
- Convert temperatures to Kelvin if given in °C or °F.
- Select the unknown variable to calculate; the calculator rearranges the equation accordingly.
- Review the formula preview and verify units; interpret the result physically (e.g., higher \(T\) at fixed \(V\) increases \(P\)).
- Record the answer with appropriate significant figures and units for reports or homework.
Core Formulas
Combined Gas Law (two states, constant moles):
Solving for unknowns:
Temperature conversions:
Examples
Example 2 — Find Final Volume
\(P_1=750\ \mathrm{mmHg}=0.9868\ \mathrm{atm}, V_1=500\ \mathrm{mL}, T_1=295\ \mathrm{K}; P_2=1.20\ \mathrm{atm}, T_2=320\ \mathrm{K}\).
Example 3 — Solve for Final Temperature
\(P_1=2.0\ \mathrm{bar}, V_1=1.2\ \mathrm{L}, T_1=280\ \mathrm{K}; P_2=1.0\ \mathrm{bar}, V_2=2.0\ \mathrm{L}\).
FAQs
Do temperatures have to be in Kelvin?
Yes. Convert all temperatures to Kelvin; using °C or °F directly gives incorrect results.
Can pressure units differ between states?
No. Ensure consistent pressure units (atm, mmHg, kPa, bar) for state 1 and 2.
When should I use the combined gas law instead of the ideal gas law?
Use the combined gas law to relate two states of the same sample (constant moles). Use \(PV=nRT\) when calculating moles is required.
What assumption does this law make about moles?
It assumes the gas amount is constant; no leaks or mass transfer between states.
Can I mix units like mL and L?
No. Convert both volumes to the same unit before calculation.
What if the gas condenses or boils?
Phase changes violate the assumptions; the law does not apply across phase transitions.
How do I convert Celsius or Fahrenheit to Kelvin?
Use \(T_\mathrm{K}=T_{^\circ\mathrm{C}}+273.15\) or \(T_\mathrm{K}=\frac{5}{9}(T_{^\circ\mathrm{F}}-32)+273.15\).
Does this account for non-ideal gas behavior?
No. Deviations occur at high pressure or low temperature; real-gas corrections like van der Waals are needed in such cases.
Can I solve for any missing variable?
Yes. Provide the other five; rearranged formulas for \(P_2\), \(V_2\), or \(T_2\) are available above.
What are common pressure conversions?
\(1\ \mathrm{atm}=760\ \mathrm{mmHg}=101.325\ \mathrm{kPa}\approx1.01325\ \mathrm{bar}\).
How many significant figures should I report?
Match the precision of input values; typically 2–3 significant figures in introductory problems.
Can I include partial pressures in mixtures?
Yes. Apply the law to each component if the amount is fixed and interactions are negligible.