The value cited for the apparent K1 of carbonic acid, 4.3 10-7, is the one normally

Question:

The value cited for the "apparent K1" of carbonic acid, 4.3 10-7, is the one normally given in reference books. It is determined by measuring the pH of water to which a known amount of carbon dioxide has been added. When we recall that only 0.3% of carbon dioxide is converted to carbonic acid in water, what is the "true K1" of carbonic acid?