Question

If a gas at 740 mm Hg and 70c has its pressure lower to 720 mm Hg, what will it's temperature be if volume is held consistent

Answer 1

When the volume and quantity of the gas are held constant, we can use the Gay-Lussac's Gas Law expressed as
     P1/T1 = P2/T2
in which if the pressure of the gas decreases, we know that the temperature decreases.
We first convert the temperature to absolute temperature
     T1 = 70 + 273 = 343 K
Rearranging the Gay-Lussac's equation to solve for the final temperature 
     T2 = P2T1 / P1
           = (720 mmHg)(343 K) / 740 mmHg
           = 334 K = 61ºC