I'm studying for my Chemistry midterm which is tomorrow. I'm working the practice exam offered by my professor and am confused on two of the problems. The practice exam gives the correct answers but I have no idea HOW the answer is calculated. I even went to the tutoring center here after class today and the girl who tried to help me couldn't figure this out, so I don't know where else to turn for help. Can someone please tell me how you correctly work the following problems?
"Calculate the pH of a solution composed of 0.00606 M nitric acid and 0.00276 M hydrochloric acid."
and
"If 15 mL of 0.1 M sodium hydroxide is added to 30 mL of 0.1 M acetic acid (Ka = 1.84 x 10^-5) what is the pH of the resulting solution?"
"Calculate the pH of a solution composed of 0.00606 M nitric acid and 0.00276 M hydrochloric acid."
and
"If 15 mL of 0.1 M sodium hydroxide is added to 30 mL of 0.1 M acetic acid (Ka = 1.84 x 10^-5) what is the pH of the resulting solution?"