Chemistry
Answer
| Drying Agent | Dehydrating Agent |
|---|---|
| Drying Agents remove moisture from other substances. | Dehydrating Agents remove chemically combined elements of water in the ratio of 2:1 (hydrogen:oxygen) from a compound. |
| Drying Agents are used to dry gases like chlorine, sulphur dioxide and hydrogen chloride. They are also used in dessicators to keep substances dry. | Dehydrating Agents prepare substances such as carbon monoxide and sugar charcoal. |
| They represent a physical change. | They represent a chemical change. |
| Example: Phosphorous pentoxide (P2O5), Calcium Oxide (CaO) | Example: Conc. Sulphuric Acid H2SO4 |
Related Questions
Give reasons for the following:
(a) Sodium hydrogen sulphate is not an acid, but it dissolves in water to give hydrogen ions according to the equation
NaHSO4 ⇌ H+ + Na+ + SO42-
(b) Anhydrous calcium chloride is used in a desiccator.
Explain clearly how conc. H2SO4 is used as a dehydrating as well as a drying agent.
State whether a sample of each of the following would increase or decrease in mass if exposed to air.
(a) Solid NaOH
(b) Solid CaCl2
(c) Solid Na2CO3.10H2O
(d) Conc. Sulphuric acid
(e) Iron (III) Chloride
(a) Why does common salt get wet during the rainy season?
(b) How can this impurity be removed?
(c) Name a substance which changes the blue colour of copper sulphate crystals to white.
(d) Name two crystalline substances which do not contain water of crystallisation.