Phosphoric acid is a triprotic acid ( K a1 = 6.9 × 10 − 3 , K a2 = 6.2 × 10 − 8 , and K a3 = 4.8 × 10 − 13 ). To find the pH of a buffer composed of H 2 PO − 4 ( aq ) and HPO 2 − 4 ( aq ) , which p K a value should be used in the Henderson–Hasselbalch equation?

Covalent bonds generally form when the bonded elements have a difference in electronegativity less than 1.5. subtract the electronegativities for the following pairs of elements and predict whether they form a covalent bond. electronegativity difference of c and c: ionic covalent electronegativity difference of mg and cl: ionic covalent