If pH in stomach is 2 and person takes aspirin tab (pH 3 ) , is it possible that taking aspirin causes development of ulcer by it’s pH ? 
How ???
Just by the number, if the stomach is PH 2 and you take aspirin that ranges from from 2.8 to 3.2 , it would appear to make the stomach less acidic instead of more acidic, but that is not what happens.
The stomach’s PH varies. The normal volume of the stomach fluid is 20 to 100 mL and the pH is acidic (1.5 to 3.5). These numbers are converted to actual acid production in units of milliequivalents per hour (mEq/hr) in some cases. The stomach is constantly secreting to counteract the gastric acids and help keep a balance. When an imbalance is allowed to remain for too long, the lining of the stomach wears aware, leading to an ulcer. Alkaline producing food help maintain proper PH balance in the stomach, foods like yogurt help to maintain a good bacterial balance for a health body.