Study the ph of acids and bases (hcl and naoh) on the basis of their reaction with
Answers
Answer:
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Explanation:
Aim:
To study the properties of acids (dilute HCl) and bases (dilute NaOH) by their reactions with the following:
Litmus solution (red/blue)
Zinc metal
Solid sodium carbonate
Materials required:
Test tube
Test tube stand
Cork
Test tube holder
Boiling tube
Droppers
Flat bottom flask
Burner
Match box
Beaker
Thistle funnel
Litmus paper/solution
Fresh lime water
Glass rod
Dilute HCl
Dilute NaOH
Zinc granules
Solid sodium carbonate
Theory:
What is acid?
Chemical species which donate proton or release H+ ions when dissolved in water are called acid. They turn blue litmus solution to red colour.
Hydrochloric acid reacts with zinc metal to produce zinc chloride and hydrogen gas. The reaction is given below:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Hydrochloric acid reacts with Na2CO3 to produce carbon dioxide and turns the lime water milky as it forms calcium carbonate. The milkiness formed is disappeared when more than necessary carbon dioxide is passed through the solution. The reaction is as follows:
Na2CO3(s/aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)
Experimental Setup for Litmus Test Procedure:
HCl reacts with blue litmus solution
Take a test tube stand and place two test tubes in it.
Label the test tube as test tube 1 and test tube 2.
Add 5 ml of blue litmus solution to test tube 1.
Add 5 ml of red litmus solution to test tube 2.
Use a dropper and add equal drops of hydrochloric acid in the both test tubes.
Wait and observe the colour change.
Experimental Setup for Reaction with Zinc metal:
HCl reacts with Zinc metal
Procedure
Take a clean and dry test tube.
Add zinc granules in it.
Submerge the zinc granules in the test tube by adding hydrochloric acid to it.
Close the mouth of the test tube with cork which has a glass delivery.
A robust explosion takes place between 2-3 minutes liberating colourless and odourless gas.
When a burning match stick in got near the glass tube mouth the gas burns with a pale blue flame with a pop sound.
Reaction:
2HCl(aq) + Zn(s) → ZnCl2(aq) + H2↑
Experimental Setup for Reaction with solid sodium carbonate:
HCl reacts with solid sodium carbonate
Procedure
Take a flat bottom flask with 1 gm of solid sodium carbonate and some distilled water.
Take a clean and dry double bore cork and thistle funnel which has a delivery tube fitted to it.
Close the mouth of flat flask with the double bore cork.
Add 2 mL of dilute hydrochloric acid.
Colourless and odourless gas is liberated which is passed through the lime water using the delivery tube.
The colour of the lime water is changed to milky.
Reaction:
Na2CO3(s/aq) + 2HCl(aq) –→ 2NaCl(aq) + CO2↑+ H2O(l)
Ca(OH)2(aq) + CO2↑ –→ CaCO3(s) + H2O(l)
CaCO3(s) + H2O(l) + CO2(g) –→ Ca(HCO3)2(aq)
Observation:
Experiment Observation
Litmus test The blue litmus solution in test tube 1 turns red whereas there is no change in colour observed in the test tube 2 containing red litmus solution.
Reaction with Zinc metal Acids such as hydrochloric acid (HCl) liberate hydrogen gas when reacted with active metals such as zinc and burns with a pop sound when burning splinter is got near it.
Reaction with Na2CO3 Sodium carbonate and hydrochloric acid react to produce carbon dioxide gas and turns lime water milky. When excess gas is passed the milkiness is disappeared.
Result and Conclusion:
In the litmus test experiment the blue litmus solution turns to red when hydrochloric is added. Therefore acids such as HCl show acidic character.
Hydrochloric acid reacts with active metals such as zinc to form zinc chloride and liberate hydrogen gas.
HCl reacts with sodium carbonate to liberate carbon dioxide gas.
Therefore from the above three points we can conclude that HCl (Hydrochloric acid) is acidic in nature.
Precautions to be taken during the experiment:
Conduct the experiment in clean test tubes.
HCl is corrosive in nature and should be handled with great care.
Take small amount of chemicals to perform the experiments.
While shaking the solution and reaction mixture do not spill.
Whenever you conduct a test for hydrogen, conduct it with the least amount of gas.
To get quick results for lime water test, pass carbon dioxide gas through the solution and shake the test tube by placing your thumb on its mouth.