Studying the properties of acids and bases (HCl & NaOH) on the basis of their reaction

Experiment A


Aim

To study the properties of acids (dilute HCl) by their reaction with
i) Litmus solution (Blue/Red)
ii) Zinc metal
iii) Solid Sodium Cabonate

Materials Required

  • Test tubes
  • Test tube stand
  • Delivery tube with cork
  • Litmus solutions (blue and red)
  • Zinc metal (granulated)
  • Solid sodium carbonate
  • Sodium hydroxide solution
  • Distilled water
  • Lime water

Principle

An acid can be tested as follows:

  • It turns blue litmus red.
  • Most of the dilute acids liberate hydrogen gas with active metals like zinc.
    Zn + 2HCl → ZnCl2 + H2
  • With carbonates, dilute acids gives carbon dioxide. For example, dill. HCL gives CO2 with sodium cabonate, Na2CO3.
    Na2CO3 + 2HCL → NaCl + H2O + CO2

Procedure

  • Take nearly 5 ml of the given acid in a test tube. Dilute it with nearly 10 mL of distilled water.
    In two test tube take nearly 1 mL each of red and blue litmus solution. To each of the test tube add 2-3 drops of the diluted acid. Note the colour of the two solutions.
  • Take a small piece of granulated Zinc in a test tube. Add to it nearly 2mL of diluted acid. If there is no reaction, wait for 5 minutes or till a vigorous reactions starts. Fit a cork with a delivery tube in the mouth of the test tube in the month of the test tube and perform the following experiments.
    (i) Note the colour of the gas evolved.
    (ii) To note the odour of the gas evolved, fan the gas gently towards your nose.
    (iii) Ignite the gas coming out of delivery tube. Note the colour of the flame produced.
  • Take a pinch of the solid sodium carbonate in a clean and dry test tube. Add to it 1-2 mL of dilute acid. A vigorous reaction starts. Note the colour of the gas evolved. Pass the gas through freshly prepared lime water and observe the changes produced.
    To note the odour of the gas evolved, fan the gas gently towards your nose.

Observations

S. No.ExperimentObservation
1.(a) Colour developed with blue litmus solution.
(b) Colour developed with red litmus solution.
No change in colour.
Blue.
2.Treat some granulated zinc with dil. NaOH solution in a
test tube fitted with a cork and delivery tube.
A colourless, odourless gas is evolved. The gas
burns with a blue flame.
3.Add a pinch of sold sodium carbonate to the NaOH
solution.
Neither any gas is evolved nor any precipitate
is formed.

Inference :- Dilute acid turns blue litmus red, liberates hydrogen with active metals like Zinc and gives CO2 with solid sodium carbonate.

Precautions

  • Wash and clean the test tubes before starting the experiment.
  • Ignite the hydrogen evolved carefully. Hydrogen forms an explosive mixture with oxygen. Therefore, use a test tube with a delivery tube to carry out this test.
  • When treating zinc with dilute acid, please see that there is no naked flame near you.
  • Handle dilute hydrochloric acid solution very carefully.

Experiment B


Aim

To study the properties of bases (dilute NaOH) by their reaction with
i) Litmus solution (Blue/Red)
ii) Zinc metal
iii) Solid Sodium Cabonate

Materials Required

  • Test tubes
  • Test tube stand
  • Litmus solutions (blue and red)
  • Zinc metal
  • Solid sodium carbonate
  • Distilled water

Principle

A base can be tested as follows :

  • It turns red litmus blue.
  • It liberates hydrogen with metals like Al, Si, Zn, Sn, etc. For example, hot dilute NaOH liberates H2 with Zn as follows :
    Zn + 2NaOH → Na2ZnO2 + H2

    Na2ZnO2 – Sodium zincate

Procedure

Dissolve 2-3 small pieces of sodium hydroxide in nearly 10 mL of distilled water and test it as follows :

  • Take nearly 1 mL each of red and blue litmus solutions in two different test tubes. Add 1 drop of NaOH solution to both and observe the colour changes produced (if any).
  • Take nearly 5 mL of NaOH solution in a test tube. Add to it two or three small pieces of zinc metal. Wait for sometime till a reaction starts. Now fit a cork with a delivery tube in a month of test tube and perform the followings experiments :
    (i) Note the colour of the gas produced.
    (ii) To note the odour of the gas produced, fan the gas gently towards your nose.
    (iii) Ignite the gas coming out of delivery tube and note the colour of the flame produced.
  • Take 5 mL of NaOH solution in a test tube. Add to it a pinch of solid sodium carbonate. Record your observations in your notebook.

Observations

S.No.Experiment Observation
1.(a) Colour developed with blue litmus solution.
(b) Colour developed with red litmus solution.
No change in colour.
Blue.
2.Treat some granulated zinc with dil. NaOH solution in a
test tube fitted with a cork and delivery tube.
A colourless, odourless gas is evolved. The gas
burns with a blue flame.
3.Add a pinch of sold sodium carbonate to the NaOH
solution.
Neither any gas is evolved nor any precipitate
is formed.

Inference : A solution of NaOH in water turns red litmus into blue, librates hydrogen with zinc, and it doesn’t react with solid sodium carbonate.

Precautions

  • Wash and clean the test tube before starting the experiment.
  • Ignite the hydrogen evolved carefully. Hydrogen forms an explosive mixture with oxygen. Therefore, use a test tube fitted with a cork and delivery tube to perform this test.
  • While treating zinc with dil. NaOH, please see that there is no naked flame near you.

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