ENRICHMENT ACTIVITY (P2) Subject: Chemistry Name of the student:
Date: Exam No:
Marks: 5 Universal Indicator: Universal indicator can display so many colours because it is actually a mixture of several indicators. Universal indicator can show us much more accurately the strength of an acid or a base.
pH Scale : ❖ The strength of acids and bases depends on the number of H+ ions and OH- ions produced. Acids that give rise to more H+ ions are said to be strong acids, and acids that give less H+ ions are said to be weak acids. Same is the case with bases also. ❖ A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. ❖ pH stands for power of H+ or Potential of H+. H+ plays an important role in knowing how acidic or basic a solution is. ❖ The pH of a neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution. As the pH value increases from 7 to 14, it represents an increase in OH -ion concentration in the solution, that is, increase in the strength of alkali. Answer the following: 1. You have two solutions A and B. The pH of A is 6 and pH of B is 8. Which of these two have higher hydrogen ion concentration. A will have more Hydrogen ion concentration as pH is 6 which indicates its acidic. Acids have Hydrogen ion. Whereas pH of B is 8 which indicate its basic and will have less hydrogen ion. 2. Which is more acidic orange juice or tomato juice? Why? Orange juice will be more acidic than tomato juice as pH of orange juice is 3 while tomato juice is 4. Which indicates that orange juice has more hydrogen ion concentration than tomato juice. So orange juice will be more acidic than tomato juice. 3. Write the names of 2 strong bases. Bleach and soapy water 4. What is the nature of common salt? Why? NaCl is common salt formed after neutralization reaction of acids and base . Nature of common salt is neutral with pH value 7
5. The colour shown by 5 solutions by the universal indicators are given below. A- Yellow, B- Blue, C- Red, D- Orange, E – Purple (i) Which is having the highest pH value? E