The molar volume of an ideal gas at one atmosphere and ${273}^{0}C$ is

At 273 K and 1 atm pressure, gas occupies 22.4 litres molar volume. In the given question, pressure = 1 atm, n = 1 mol and temperature =273⁰C=546 K. 

546 K is double of 273 K.

As volume is directly proportional to temperature, at constant pressure. When the temperature doubles, the volume also doubles. 

Thus, at 546 K and 1 atm pressure, an ideal gas would occupy 44.8 L of molar volume.