Is blood less acidic when carbon dioxide exits?

It helps to take a look at the Carbonic-Acid-Bicarbonate Buffer reaction:

H+ + HCO3- ⇔ H2CO3 ⇔ H2O + CO2

When there is an accumulation of carbon dioxide, the reaction shifts to the left, increasing H+ ions, meaning the pH decreases (more acidic). When carbon dioxide is taken out of the system, the reverse happens and the blood becomes less acidic.