The pressure change when a constant volume of gas is heated from 20.0°C to 40.0°C is an increase of 0.07 atm.
To determine the pressure change when a constant volume of gas at 1.00 atm is heated from 20.0°C to 40.0°C, we can use the ideal gas law equation: PV = nRT.
Since the volume is constant, we can simplify the equation to P1/T1 = P2/T2, where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the final pressure and temperature.
Using the given temperatures in Kelvin, T1 = 20.0 + 273 = 293 K and T2 = 40.0 + 273 = 313 K.
Substituting these values into the equation, we get P1/293 = P2/313. Solving for P2, we have P2 = P1 * (T2/T1).
Plugging in the values, P2 = 1.00 atm * (313/293) = 1.07 atm.
Therefore, the pressure change when the gas is heated from 20.0°C to 40.0°C is an increase of 0.07 atm.