Calculation of Time Required for Pressure to Rise
Given data:
- Rate constant for disappearance of A: 8×10^-3
- Initial pressure of A: 0.1 atm
- Final pressure of A: 0.145 atm

We can use the first-order rate equation to calculate the time required for the pressure of A to rise from 0.1 atm to 0.145 atm.

The first-order rate equation is: ln[A] = -kt + ln[A]0

Where:
- [A]0 is the initial concentration of A
- [A] is the concentration of A at time t
- k is the rate constant

We can rearrange this equation to solve for time t:

t = (ln[A]0 - ln[A]) / k

Substituting the given values, we get:

t = (ln(0.1) - ln(0.145)) / 8×10^-3
t = 12.9 seconds (approx.)

Therefore, it will take approximately 12.9 seconds for the pressure of A to rise from 0.1 atm to 0.145 atm.

Calculation of Total Pressure After 100 Seconds
Given data:
- Rate constant for disappearance of A: 8×10^-3
- Initial pressure of A: 0.1 atm
- Time elapsed: 100 seconds

We can use the first-order rate equation to calculate the concentration of A at time t:

ln[A] = -kt + ln[A]0

Substituting the given values, we get:

ln[A] = -8×10^-3 x 100 + ln(0.1)
ln[A] = -0.527

Converting this back to pressure, we get:

[A] = e^-0.527
[A] = 0.590 atm

Therefore, the pressure of A after 100 seconds is 0.590 atm.

To calculate the total pressure in the system, we need to consider the other gases present in the system. If we assume that the other gases do not react and their concentrations remain constant, then the total pressure in the system after 100 seconds would be:

Total pressure = Pressure of A + Pressure of Other Gases
Total pressure = 0.590 atm + Pressure of Other Gases

The pressure of the other gases can be determined from the ideal gas law:

PV = nRT

Where:
- P is the pressure
- V is the volume
- n is the number of moles
- R is the gas constant
- T is the temperature

If we assume that the volume, number of moles, and temperature remain constant, then the pressure of the other gases remains constant as well. Let's assume that the pressure of the other gases is 0.5 atm. Then, the total pressure in the system after 100 seconds would be:

Total pressure = 0.590 atm + 0.5 atm
Total pressure = 1.09 atm

Therefore, the total pressure in the system after 100 seconds would be 1.09 atm.