To Study the Properties of Acids and Bases – MeitY OLabs

To Study the Properties of Acids and Bases – MeitY OLabs


Properties of Acids and Bases According to Arrhenius concept of acids and
bases, an acid is a substance which releases one or more H+ ions in aqueous solution whereas
base is a substance which releases one or more OH- ions in aqueous solution. Many of
the food items that we consume contain acids and bases and their presence can be identified
with sour and bitter tastes. Substances with a sour taste are often regarded as acids.
Lemon juice, vinegar, grape fruit juice, etc. are examples of acids. Similarly substances
with bitter taste and soapy touch are regarded as bases. Caustic soda, caustic potash, slaked
lime, etc., are examples of bases. In this experiment, our aim is to study the
properties of acids and bases HCl and NaOH by their reaction with litmus solution and
solid sodium carbonate. Materials required: Litmus solution blue and red, HCl, NaOH, dropper,
test tubes, sodium carbonate, boiling tube, round bottom flask, phenolphthalein, lime
water, spatula, double bore cork, bent tube, thistle funnel and stand with clamp, Procedure: To study the action of HCl and NaOH on litmus
solution, add a few drops of blue litmus solution in one test tube and red litmus solution in
another test tube. Place both the test tubes in a test tube stand and add a few drops of
HCl in each test tube. You can see that the blue litmus solution changes to red. From
this we can infer that HCl is an acid having pH value below 7. Similarly add a few drops
of NaOH to red litmus solution and blue litmus solution which is taken separately in two
other test tubes. You can see that red litmus solution changes to blue which indicates that
NaOH is an alkali having pH more than 7. To study the action of HCl and NaOH on solid
sodium carbonate, first clamp the round bottom flask to the stand and add a small quantity
of sodium carbonate and few drops of distilled water into it. Close the mouth of the flask
with a double bored cork and insert a thistle funnel and a bent tube into the two different
holes of the rubber cork. Now pour a small quantity of lime water into the boiling tube
and clamp it in another stand. Then add HCl to the sodium carbonate solution in the flask
using the thistle funnel. You can see that a gas evolves and passes through the lime
water and turns it milky. Here due to the action of HCl on sodium carbonate, carbon
dioxide is formed which turns lime water milky. 2HCl + Na2CO3 ? 2NaCl + CO2 +H2O
CO2 + Ca (OH) 2 ? CaCO3 +H2O Now add a small amount of sodium carbonate
in a boiling tube and add NaOH solution into it. Then shake the boiling tube well. Add
a few drops of phenolphthalein into it. We can observe that the colour of the solution
turns pink which indicates that both sodium carbonate and NaOH do not react but form an
alkaline solution. Precautions: Add HCl to sodium carbonate only after making
the apparatus airtight, otherwise the gas evolved in the reaction will get away through
the gap. Handle the chemicals HCl and NaOH carefully
as they are harmful.

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