STP means standard temperature and pressure. This 273˚K and 760 mm Hg

Use the following equation.

P1 * V1 ÷ T1 = P2 * V2 ÷ T2

The temperature must be in ˚K.

T1 = 100 * 273 = 373

720 * 400 ÷ 373 = 760 * V ÷ 273

V * 283,480 = 7.8624 * 10^7

V = 7.8624 * 10^7 ÷ 283,480

The new volume is approximately 277 ml.

Nitrogen monoxide.....

Use the combined gas law. Assume that all of the data are expressed to three significant digits.

P1V1 / T1 = P2V2 / T2 .............. combined gas law

V2 = P1V1T2 / (T1P2) ............... solve for V2

V2 = 720. torr x 400. mL x 273K / 373K / 760 torr

V2 = 277 mL