Tiêu đề Chapter - 2 Acids_Bases_and_Salts.pdf ✅

NaOH (aq) → Na+ (aq) + OH- (aq) The presence of hydroxide ions [OH-] in sodium hydroxide solution makes it behave like a base. pH Scale ● pH of a solution: pH of a solution is the negative logarithm to the base 10 of the hydrogen ion concentration expressed in mole per litre. pH = –log10 (H+) p H = 7 - Neutral [H+] = [OH-] pH less than 7 - Acidic [H+] more than [OH-] pH more than 7 - Basic [OH-] more than [H+] Universal Indicator In case of a colourless liquid, the accurate pH can be obtained by adding a universal indicator. It is a mixture of several indicators and shows different colours at different concentration of hydrogen ions in a solution. Variation of pH with the change in concentration of H+ (aq) and OH– (aq) ions For Example: i. A universal indicator produces green colour in a neutral solution, pH = 7. ii. The colour changes from blue to violet as pH increases from 7 to 14. iii. The colour changes from yellow to pink and then to red as pH decreases from 7 to 1. pH of some common substances shown on a pH paper (colours are only a rough guide) Importance of pH in everyday life pH change and survival of animals ● Our body works well within a narrow pH range of 7.0 to 7.8. ● When the pH of rain water is less than 5.6, it is known as acid rain.