a 4 L sample of gas at 30 degrees celcius and 1 atm is changed to 0 degrees celcius and 145,000Pa. what is its new volume?

(P1V1)/T1 = (P2V2)/T2

Note the correct spelling of Celsius.
Don't forget to change temperature to Kelvin. You also will need to convert pressure to the same units. 1 atm = 101,325 Pa.

is the answer .397 liters?

No, not even close.

Show your work and I can find the error. Did you change 145,000 Pa to atm? Did you change 30 C and zero C to Kelvin?

1(4)/1.42v2=303.15/273.15

Your numbers look ok to me. You just didn't solve for V2 correctly. If I solve for V2, I get

[1(4)*273.15]=1.42*303.15*V2 and
V2 = [(1*4*273.15)/(303.15*1.42)]=??

I might disagree just a little over the conversion of Pa to atm. I would have written 145,000/101325 = 1.4310 and I wouldn't have rounded to 1.42 since you used 273.15 and 303.15 to more places. But your numbers, otherwise, look ok. I get 2.5186 L if 1 and 4 are to that many significant figures.

To find the new volume of the gas, we can use the combined gas law equation:

(P1 * V1) / (T1) = (P2 * V2) / (T2)

Where:
P1 = initial pressure of the gas in Pa
V1 = initial volume of the gas in L
T1 = initial temperature of the gas in Kelvin
P2 = final pressure of the gas in Pa
V2 = final volume of the gas in L
T2 = final temperature of the gas in Kelvin

First, let's convert the given temperatures from degrees Celsius to Kelvin:

Initial temperature (T1) = 30°C + 273.15 = 303.15 K
Final temperature (T2) = 0°C + 273.15 = 273.15 K

Now, let's plug in the given values into the combined gas law equation and solve for V2:

(1 atm * 4 L) / 303.15 K = (145,000 Pa * V2) / 273.15 K

To solve for V2, we can cross-multiply and then divide:

1 atm * 4 L * 273.15 K = 145,000 Pa * V2 * 303.15 K

1092.6 L*atm = 438,513,000 Pa*L

V2 = (1092.6 L*atm) / (438,513,000 Pa)

Simplifying the units gives us:

V2 = 0.002494 L

Therefore, the new volume of the gas is approximately 0.002494 L.