help with homework please??!?!??!?

Question

A gas has a volume of 400 mL at a pressure of 3 atm and a temperature of 127 °C. What would its volume be at STP?

thanks in advanced

Answer 1

STP is 1 atm at 293°K (20°C). Convert 127°C into °K.
127°+273°=400°.
Use the Ideal Gas Law, PV=nRT, to find new volume. Note that n (amount of gas in moles and R, the gas constant are constant and can be eliminated from calculations). P1/P2*V1/V2=T1/T2, or, V2=V1*P1/P2*T2/T1 (I used algebra to rearrange the formula).
V2=400ml*(3/1)*(293/400)=879 ml.
Note that temperature will reduce volume to 75%, but pressure will increase volume three times, so the answer of more than double is correct.