Understanding Acid-Base Titration, How It Works, Formulas, Examples of Problems

Titration becomes a quantitative analysis method in determining the content of a substance that is most widely used especially in acid-base titration. The reaction of acids with bases to form a salt and water is one of the characteristics of a chemical reaction that is very common in the laboratory because there are so many compounds that can act and have acidic or basic properties.

Therefore the principle of neutralizing reaction from acid-base is most often applied in determining the level of an unknown substance through acid-base titration . In this article, we will discuss the definition of acid-base titration, how titration works, the type of titration, titration formulas and calculations, and examples of questions and answers.

table of contents

  • Acid-base titration
    • How Titration Works
    • Terms in Titration
      • Titran (Standard Solution)
      • Titrate (Analytic Samples)
      • Equivalent Point
      • Indicator
      • Titration Endpoint
    • Type of Acid Base Titration
      • Alkalimetry Titration
      • Acidimetry Titration
    • Titration Formulas and Calculations
    • Examples of Questions and Answers
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Acid-base titration

Titration is a procedure used in chemistry to determine the concentration or content of an unknown substance by using a substance that has known levels. In acid-base titration, the principle is that an acidic substance will be titrated with an alkaline solution whose levels are known or a base which is titrated with a known acid solution.

The principle of acid-base titration applies the principle of acid-base reactions where when an acid and base are mixed or reacted, a neutralizing reaction will result in a salt and water with a neutral pH.

How Titration Works

In determining the level of an unknown substance, you first need to know the nature of the substance whether it is an acid or a base that can be determined by measuring its pH.

When the substance is known, then you can determine what solution will be used to titrate the substance whether acidic or basic. In a titration, the substance being tested or sample is added to a solution which has been known to be slowly carried out so that a neutralizing reaction occurs.

When the pH in the mixture is neutral, it indicates that all the sample substances have reacted with the solution you used to titrate. The way to find out the pH of the solution is by using a pH meter, but in titration the most common way is to use an indicator.

Terms in Titration

There are several terms in this titration method that you need to know before learning more about the titration analysis method.

  1. Titran (Standard Solution)

Titran is a substance that is used as a penetration agent or commonly called a standard solution where this solution has known the exact level and will be used in determining the levels of unknown substances. In titration, the purity of the titrant is very necessary to prevent the occurrence of a mistake in the determination.

  1. Titrate (Analytic Samples)

Titrate is the opposite of the titrant where the titrate is a substance whose concentration or concentration is unknown. This titrate will be titrated with titrant so that the concentration can be calculated.

  1. Equivalent Point

In acid-base titration, when the solution has completely neutralized it means that all the moles of the titrate or sample have finished reacting with the titrant added. In this condition called the equivalence point, in other words the equivalent point is the point where the mole of the sample that reacts is the same as the mole of the titrate used.

  1. Indicator

The indicator has been mentioned in the previous discussion, this indicator is an external substance added to the titrate or sample that aims to find out when a titration must be stopped, in general the indicator works through color changes.

There are also many kinds of titration indicators based on the pH range or pH range, for example Phenolphthalein or PP is an indicator that has a pH range of 8.3-10 so that when an acid titration with a strong base has passed the equivalent point and towards a pH of about 8.3 the indicator will change color pink, at that time the titration must be stopped.

  1. Titration Endpoint

The end point of a titration is a condition where the titration must be stopped. The end point of the titration is different from the equivalent point where at the end point of the titration it is generally marked with indicators that change color. If in this condition the titration is not stopped the excess titrant will occur so that the calculation results will be incorrect.

Type of Acid Base Titration

There are 2 types of acid-base titrations which are based on the type of sample substance and also the standard solution.

  1. Alkalimetry Titration

Alkalimetry is a type of titration that uses a standard solution in the form of a base. This type of titration is the most commonly used titration.

In alkalimetry titration, if the standard solution used is strong base, the final reaction can produce neutral pH if the sample is strong acid, but will produce a basic pH (pH> 7) if the sample used is weak acid.

An example of the most common alkalimetry titration is the determination of HCl using NaOH where the reaction is a neutralizing reaction:

HCl + NaOH NaCl + H 2 O

  1. Acidimetry Titration

Acidimetry is the opposite of alkalimetry where acidimetry is a titration method that uses a standard solution in the form of acid. In acidimetric titration, when the acid used as a standard solution is strong acid, neutral pH will be obtained when the sample used is strongly alkaline as well so that the neutralization reaction will be perfect.

However, it will produce an acidic pH when the sample used tends to be weakly alkaline so that the neutralization reaction tends towards the acid.

Titration Formulas and Calculations

The purpose of the titration is to determine the level or concentration of an unknown substance by using a substance that is known as a reference.

The principle of the calculation is based on the number of moles of each substance that reacts in one titration. The principle is that in one finished reaction, the amount of substance from one reactant used is the same as the amount of other reactants that react. Thus, in acid-base titrations this can be written as acid moles and base moles.

Acid mole = base mol

We can determine the mole from concentration and volume.

Mol = Concentration x Volume

Then from the above equation it can be concluded that:

(Concentration x volume) acid = (concentration x volume) base

Or formulated

a x V a = M b x V b

For compounds that have a valence of more than 1, it can be formulated:

a x V a xn a = M b x V b xn b

Where Ma is the concentration of acid, Va is the volume of acid, na is the amount of valence of acid, Mb is the concentration of base, Vb is the volume of base, and nb is the amount of valence of base.

When you determine the level of an acid sample which means it is an alkalimetric titration, the volume of the acid sample you use can be determined freely. Then you use a base as a standard solution (titrant) with a known molarity (Mb).

The base volume (Vb) itself can be obtained from the titration results, which is when the titration has reached its final point, then you can calculate how much base volume or standard solution you used to titrate the sample.

In the titration generally used a glass tool that is specifically for the titration burette so you can see changes in the volume of the titrant before and after it is used for titration. The more volume of titrant used, the higher the concentration.

Examples of Questions and Answers

As for providing a deeper understanding, here are some examples of questions about acid-base titration and the answers. Among others;

  1. As much as 5 mL of unknown concentration of HCl solution is titrated with 1 M NaOH. In titration 10 mL NaOH is needed so that the PP indicator turns pink. Determine the concentration of HCl

The answer

a x V a = M b x V b

a x 5 ml = 1 M x 10 ml

a = 2M

Then it is known from the calculation that the concentration of HCl is 2M

  1. Determine the amount of 0.105M HCl solution used to titrate 22.5 mL of 118M NH 3 solution

The answer

HCl + NH 3  NH 4 Cl, then valence = 1

a x V a = M b x V b

0.105M x V a = 0.118M x 22.5mL

a = 25.3 mL

That was some material that can be written related to the  understanding of acid-base titration , ways of working, types, calculation formulas, sample problems and answers. Hopefully, through this review can provide insight and add in-depth education for all readers. Thanks,

 

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