alleryStart learning →Two different gases are held at the same temperature. What do their molecules share?
AThe same root mean square speed
BThe same molecular molar mass
CThe same number of collisions
DThe same average kinetic energy
Answer & Solution
Correct answer: D. The same average kinetic energy
1. The average kinetic energy of a mole of gas is three halves RT, which depends only on the temperature.
2. So at a given temperature every gas has the same average kinetic energy per mole, whatever its identity.
3. Kinetic energy is one half of mass times speed squared, so a heavier gas must move more slowly to hold that same energy.
4. Root mean square speeds therefore differ sharply between gases at one temperature, which is why the first option is the trap.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.5 The Kinetic-Molecular Theory_
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