How many moles of kr g are there in .555 liters of the gas at .918 ATM and 25 degrees Celsius?

Use PV = nRT and solve for n. Thus, n = PV/RT = (0.918atm)(0.555L)/(0.0821 L-atm/deg-mole)(298)
n = 0.0208 moles (0.021 moles to 2 sig figs)