What is the pH of a 2.5 M solution of acetic acid at equilib…

What is the pH of a 2.5 M solution of acetic acid at equilibrium? (Balanced eq: HC2H3O2(aq) + H2O(l) + ⇌ H3O+(aq) + C2H3O2−(aq);  Ka of HC2H3O2 is 1.8 × 10−5  Note, X is much smaller than original concentration, therefore you do NOT need to perform the quadratic equation. 

50.0 grams of arsenic powder is mixed with 50.0 grams of oxy…

50.0 grams of arsenic powder is mixed with 50.0 grams of oxygen gas, as noted by the following balanced equation.  How many grams of diarsenic trioxide is produced?  (Molecular masses: Arsenic = 74.92 g/mol; Oxygen = 16.00; Diarsenic trioxide = 197.84 g/mol) Balanced Equation:  4As(s) + 3O2(g) –> 2As2O3(s)