Question

Describe how you can make a buffer with sodium carbonate by adding hydrochloric acid.

Please feel free to be descriptive as possible, I'm learning most of this subject on my own.

Answer 1

Answer)

Let me start from very basic

what is buffer solution, buffer is the mixture of weak acid with its conjugate base( or mixture of weak base with its conjugate acid).

Function of buffer solution- when you add small amount of acid or base it resist the change in the pH of the solution. It means when you need reaction condition in which you do not want to change the pH of the solution you can use buffer there to maintain the pH of the solution.

You can make buffer of different pH according to your requirement. There are two types of buffer 1- Acidic buffer (is the mixture of weak acid with its conjugate base 2- basic buffer ( or mixture of weak base with its conjugate acid).

Now let's talk about how it works-

In left there are two beakers one with unbuffered basic solution of methyl orange of and second with basic buffer solution of methyl orange when you add small amount(1 mL) of HCl to both beakers then colour of unbffered solution changed because pH of the solution changes whereas second solution remains unchanged because buffer solution resist the change in pH after adding small amount of acid.

Now comes to your question

Na2CO3 + HCl = NaHCO3 + NaCl

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See this very carefully, Here Na2CO3 is a weak base. So What will happen when Na2CO3 reacts with strong acid HCl it will form its conjugate acid (NaHCO3) of weak base(Na2CO3) and NaCl.

And what have i told you about basic buffer - basic buffer is a mixture of weak base with its conjugate acid .

So mixture of Na2CO3(weak base) + NaHCO3(conjugate acid of Na2CO3) is your basic buffer solution.

And what do i mean by conjugate acid or conjugate base.

when you add H+ to base you will find conjugate acid of base .

Na2CO3(base) + H+ = NaHCO3(conjugate acid) + Na+

similarly when you remove H+ from acid you will get its conjugate base.

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I have tried to explain as much as possible.... if you still have any doubts please feel free to put down in comment box i would like to answer them...

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