170135_inorganicventures_flipping

11:4 Acid Digestions of Inorganic Samples

Nitric Acid Diges-ons: Facts about nitric acid

Ø The highest valence of nitrogen is +5. This is the valence of nitrogen in nitric acid. All three N-O bonds are sp2 hybrid and the NO3- molecule is planar and symmetrical. Ø The oxidizing ability of nitric acid decreases (reducCon potenCal decreases) as the concentraCon decreases. Below 2M, the oxidizing ability is nearly eliminated.

11:5 Acid Diges-ons of Inorganic Samples

Nitric Acid Diges-ons: Facts about nitric acid (cont) ❏ Nitric acid undergoes both one and three electron changes. As illustrated above with reac8on (2) the one electron change is observed when concentrated. In comparison, the 3 electron change is observed when dilute in reac8on (3). The presence of brown fumes is indica8ve of reac8ons going by 1 electron.

⇔ NO 2

(4) H 3

O + + HNO 3

+ e -1

↑ (brown) + 2H 2 ⇔ NO ↑ (clear) + 5H 2

O : Concentrated

(5) 3H 3

O + + HNO 3

+ 3e -1

O : Dilute

❏ Nitrate is generally considered to be a 'poor ligand' in that it's coordina8on ability is not enough to keep hydrolysis from occurring. This statement may be contradicted in certain inorganic text books.