Read Connected Gases: Conserve Moles, Not PV Alone
The two containers reach one common pressure while each stays at its own maintained temperature. Count moles in each container before and after opening the valve.
Motion and force questions become simpler when direction, starting condition, time and the acting forces are marked first.
Start with the condition
After equalisation write the same sum with one unknown pressure P and the two original temperatures.
Build the governing relation
The common pressure should lie between the initial pressures here, but it is a temperature-weighted result rather than a volume-weighted arithmetic average.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
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- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
Writing one combined PV = nRT with a single temperature is invalid because the two reservoirs are held at different temperatures.
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