IX. Acid + Metal →Salt + Hydrogen- Sulfuric acid is added to a solid strip of zinc:
H++ Zn →H 2 + Zn2+ - A piece of magnesium is dropped into a beaker of 6 M hydrochloric acid:
Mg + H+→Mg2++ H 2 - Calcium metal is added to a solution of 4 M HCl:
Ca + H+→Ca2++ H 2
Some Common Departures
- Lead shot is dropped into hot, concentrated sulfuric acid:
Pb + H+SO 4 2–→PbSO 4 + SO 2 + H 2 O
Note the departure from the general guideline.- Solid copper shavings are added to a concentrated nitric acid solution. (This reaction
is well known and is covered quite extensively in textbooks. Note how it departs
from the guideline.)
Cu + H++ NO 3 – →Cu2++ H 2 O + NO 2
X. Base + Amphoteric Metal →Salt + Hydrogen Gas
Amphoteric metals (such as Al, Zn, Pb, and Hg) have properties that may be intermediate
between those of metals and those of nonmetals. They will react with a base to form a
complex ion with oxygen. This is a rare problem. - A piece of solid aluminum is added to a 6 M solution of sodium hydroxide:
Al + OH–→AlO 33 - + H 2 - A solid piece of zinc is added to a 6 M solution of potassium hydroxide:
Zn + OH–→ZnO 22 - + H 2
XI. Strong Acid + Salt of Weak Acid →Salt of Strong Acid + Weak Acid - Hydrochloric acid is added to potassium acetate:
H++ Ac–→HAc (Do not dissociate a weak acid.) - A 9 M nitric acid solution is added to a solution of potassium carbonate:
H++ CO 32 - →H 2 CO 3
XII. Weak Acid + Weak Base →Conjugate Base + Conjugate Acid - A solution of ammonia is mixed with an equimolar solution of hydrofluoric acid:
NH 3 + HF →NH 4 ++ F– - Acetic acid is added to a solution of ammonia:
HC 2 H 3 O 2 + NH 3 →CHO 2 32 - + NH 4 +
Writing and Predicting Chemical Reactions