Laboratory Activity 7.3.3: Relationship between the pH value and molarity of acidic solutions and an alkali |
Problem statement: What is the relationship between the pH values and molarities of acidic and alkaline solution?
Hypothesis:
» | The higher the molarity of an acidic solution, the lower is its pH value. | |
» | The higher the molarity of an alkaline solution, the higher is its pH value. |
» | Fixed variable : Types of acid and alkali | |
» | Manipulated variable : Molarity of acidic and alkaline solutions | |
» | Responding variable : pH value |
Material: » Hydrochloric acid (0.001M, 0.01M, 0.1M, 1M) » Sodium hydroxide (0.001M, 0.01M, 0.1M, 1M) |
Apparatus: » Beaker » Measuring cylinder » pH meter |
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► | Hydrochloric acid
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► | Sodium hydroxide solution
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► | The pH value of the acid decreases as its molarity increases. The concentration of H+ ion is higher at higher molarity. The higher the H+ ion, the lower is the pH value. | |
► | The pH value of the alkaline increases as its molarity increases. The concentration of OH- ion is higher while the concentration of H+ ion is lower. The lower the H+ ion, the higher is the pH value. |
► | The pH value of an acid decreases as the molarity of the acid increases. | |
► | The pH value of an alkali increases as the molarity of the alkali increases. | |
► | The hypothesis is accepted. |
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