This is solved using the ideal gas law equation PV = nRT
I like to make a little table of given amounts and the constant (R) to make sure I am consistent with units
R = 8.314 x 103 L x Pa K-1mol-1 or it can be written 8.314 x 103 L x Pa
K x mol
P = 2.5 kPa (but I need pressure in Pa) 2.5kPa x 1000 Pa/1 kPa = 25000 Pa
V = ?
n = moles? (but I'm given grams) 10 g Ar x 1 mol Ar /39.9 g Ar = 0.2506 mol Ar (using Molar Mass of Ar)
T = 157 C (but I need temperature in K) 157C +273 = 430 K
Plugging these into PV = nRT or V = nRT/P will give you your final answer. Pay attention to sig figs as needed.