The volume of a gas is 400.0  mL when the pressure is 1.00 atm. At the same temperature, what is the pressure at which the volume of the gas is 2.0 L?

This problem can be solved using Boyle's Law, which states that the pressure and volume of a gas have an inverse relationship when temperature is held constant. In mathematical terms, P1V1 = P2V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume.

Step 1: Identify the knowns. P1 = 1.00 atm (initial pressure) V1 = 400.0 mL (initial volume) V2 = 2.0 L (final volume)

Step 2: Convert all volumes to the same units. 1 L = 1000 mL, so V2 = 2.0 L = 2000 mL

Step 3: Substitute the known values into Boyle's Law and solve for P2 (final pressure). P1V1 = P2V2 1.00 atm * 400.0 mL = P2 * 2000 mL P2 = (1.00 atm * 400.0 mL) / 2000 mL P2 = 0.20 atm

So, the pressure at which the volume of the gas is 2.0 L is 0.20 atm.