Question
20 [4) (1 Point) A solution of potassium carbonate, made up using tap water, was found to be cloudy. This could result from the tap water containing A lithium ions B calcium ions C sodium ions D ammonium ions. You may wish to use the data booklet to help you. A B
Answer
4.5
(195 Votes)
Una
Master · Tutor for 5 years
Answer
B
Explanation
Solutions of potassium carbonate become cloudy when there contains ions that enter into a reaction with the potassium carbonate to form an insoluble substance. This phenomenon can be explained via the principles of chemistry, and specifically through the knowledge of precipitate reactions. Precipitates are insoluble ionic solid products of a reaction, formed when the cations and anions in two solutions react to form an insoluble ionic solid. Here, the concept to apply is the Solubility Rules, where certain ions form precipitates because they make a solid substance when they come together.It is almost common knowledge in chemistry that salts (like carbonate salts) formed with group 2 elements (like Calcium) are insoluble in water. Lithium, Sodium and Ammonium ions are all soluble and therefore should not form a precipitate. However, when potassium carbonate combines with calcium ions (Group II elements), it forms an insoluble substance "Calcium carbonate (CaCO3)" which being insoluble can't dissolve in water and hence it makes the water appear cloudy.