Determine the molar mass of each of the following gases: a) 2.90 g of a gas that occupies 0.500 L at 0 degrees C and 1.00 atm (STP); b) 1.43 g of gas that occupies 2.00 L at 0 degrees C and 760 mmHg (STP); c) 0.726 g of a gas that occupies 855 mL at 1.20 atm and 18 degrees C; d ) 2.32 g of a gas that occupies 1.23 L at 685 mmHg and 25 degrees C.