Laboratory Activity 7.1.1: Role of water to show properties of acids |
Problem statement: Does water need to be present to enable an acid to show its properties?
Hypothesis: Water needs to be present to enable an acid to show its properties.
Variable:
» | Fixed variable : Ethanoic acid, test on acid | |
» | Manipulated variable : Presence of water | |
» | Responding variable : Acidic characteristics |
Material: » Ethanoic acid glacial » Ethanoic acid aqueous solution » Litmus paper |
Apparatus: » Test tube » Dropper » Carbon electrodes » Connecting wires » Crocodile clip » Electric bulb » Beakers » Batteries |
► | The animation below shows the arrangement and results of the experiment.
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► | (A) Litmus paper test
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► | (B) Electrical conductivity test
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► | Without water, dry acid exists in the form of molecules(CH3COOH) . There is no ion, therefore it does not exhibit the characteristics of an acid. | |||
► | In the presence of water, the acid ionizes:
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► | The presence of the ethanoate, CH3COO- and hydrogen ion, H+ cause blue litmus paper to turn red. | |||
► | Electricity is also conducted by the aqueous solution because of the presence of freely moving ions in the solution. On the other hand, glacial ethanoic acid cannot conduct electricity because of the presence of covalent molecules in it. |
► | Acid can only exhibit their acidic characteristics in the presence of water. As aqueous solution, they ionise to form freely moving H+ ions and anions which can conduct electricity and turn blue litmus red. | |
► | The hypothesis is accepted. |
⇲ For exercise(objective and subjective), download for free on Android OS. | ||
effective explanation . thank you .
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