Eduqo
General Science›Ch 2: Chemistry›Acids, Bases and Salts
Master key chemical compounds, pH scales, and common salts for competitive exams
Acids donate hydrogen ions and turn blue litmus red, while bases release hydroxide ions and turn red litmus blue. The pH scale measures this hydrogen ion concentration from 0 to 14, where 7 is neutral.
Smart Memory Hooks
| Substance / Food | Chemical Formula | Key Exam Fact |
|---|---|---|
| Washing Soda | Na2CO3·10H2O | Removes water hardness |
| Bleaching Powder | CaOCl2 | Disinfects drinking water |
| Tamarind / Citrus | Tartaric / Citric acid | Natural organic acids |
pH Scale
(Zero to fourteen scale)
Zero to fourteen scale
Values below seven indicate acidic nature while above seven are basic.
NaHCO3
(Sodium bicarbonate powder)
Sodium bicarbonate powder
It produces carbon dioxide gas on heating in baking mixtures.
CaSO4·½H2O
(Plaster of Paris)
Plaster of Paris
Used by doctors for supporting fractured bones in right position.
Litmus
(Natural dye indicator)
Natural dye indicator
Extracted from Thallophyta lichens to test solution acidity.
Washing soda has 2 water moleculesWashing soda has 10 water molecules
Na2CO3 contains 10 molecules of water of crystallization, not 2.
Pure water conducts electricity wellPure water is a bad conductor
Distilled water lacks ions; acids or salts must be dissolved to conduct.
Plaster of Paris formula is CaSO4Plaster of Paris is CaSO4·½H2O
Gypsum has 2 waters, Plaster of Paris has half a water molecule.
Q1.What is the chemical formula of Plaster of Paris?
Q2.Which natural acid is present in Tamarind?