Gas partial pressure between alveoli & surrounding capillaries & the capillaries & tissues delivered to?

Question

Also, how do the differences in partial pressures facilitate gas exchange?

Answer 1

At rest

Alveoli:

PO2 = 100 mmHg

PCO2 = 45 mmHg

Capillary surrounding alveoli (blood returning from tissue):

PO2 = 40

PCO2 = 45

Capillary after exchange

PO2 = 100

PCO2 = 40

At tissue

PO2 = 40

PCO2 = 45

As you can see there is a gradient for these gases to diffuse.