This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'pKa of lidocaine: \nSelect and explain. \nA. 8.1, B. 8.9, C. 7.8, D. 7.6', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Lidocaine hydrochloride is very soluble in water and alcohol and soluble in chloroform, but it is insoluble in ether. Lidocaine hydrochloride has a pKa of 7.86. Gebauer et al. developed a method for the study of lidocaine and oxycodone stability in a rectal gel.\nThe dissociation constants (pKa) for popular local anesthetics used in dentistry are:\nMepivacaine 7.6\nEtidocaine 7.7\nLidocaine\xa07.9\nPrilocaine 7.9\nBupivacaine 8.1\nTetracaine 8.5\nProcaine 9.1\nRef: Monheim’s Local anesthesia 1st\xa0 ed page no 130', 'role': 'assistant'}]