Step 1
Gay-Lussca's Law is used here.
It states that the pressure of a given mass of gas varies directly with the absolute temperature when the volume is kept constant.
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Step 2
Mathematically:
P1/T1 = P2/T2 (1)
Data provided:
Conditions 1 => P1 = pressure 1 = 750.0 mmHg; T1 = absolute temperature = 323.0 K
Conditions 2 => P2 = unknown; T2 = 273 K
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Step 3
P2 is cleared from (1):
P1/T1 x T2 = P2
(750.0 mmHg/323.0 K) x 273 K = 634.0 mmHg
Answer: P2 = 634.0 mmHg