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Normality is defined as the number of grams that is equal to the solute mixed in per liter of the solution. This method is generally used to express the concentration of the solute dissolved in a solution. The formula for normality is given by,
N = Weight of Solute in gm. / Equivalent Weight × Volume in ltr.
Concentration is the amount of solute dissolved in the given amount of solution. The SI unit for Normality is gram per liter. It can be used as a reactive species in the solution. It is also used for the quantitative measurement of the substance during the chemical process.
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Key Terms: Normality, Concentration of Solution, Molarity, Solute, Solvent, Equivalent Mass, Redox Reaction.
What is Normality?
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Normality is used to identify the concentration of the given solution during the particular chemical process. In other words we can say Normality is the number of grams which are equivalents of solute present in per liter of the solution. Normality is denoted by the symbol ‘N’. The International SI unit is gram/ liter. This is also known as an equivalent concentration.
Some of the properties of Normality of a Solution may include
- It is mainly used to measure the concentration of the solution.
- In some processes like precipitation reaction, normality is used. The main aim in this is to identify the number of ions which are precipitated during the reaction.
- The process is used in redox reactions. The number of electrons is measured.
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Calculation of Normality
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To identify or measure the value of Normality, there are some steps that need to be followed perfectly. 'Normality' is used to measure the concentration of the given solution. The steps for the calculation are
- First step is to collect the information of the equivalent weight of those reacting species which are used in the solution.
- After that, when the equivalent weight of the species is calculated then calculate the number of grams equivalent of the solute.
- Once both the values calculate the volume of the substance in liters by using the normality formula.
- The values should be kept in the right place in order to get the exact values of the solution.
Formula of Normality
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The formula of Normality is used to measure the concentration of the given solution.
When all the steps are followed perfectly then the formula for Normality is obtained. The formula is given below.
Normality = Number of Gram Equivalents / Volume of Solution in liters
Therefore,
No.of Equivalent Gram = Weight of Solute / Equivalent Weight of Solute
Hence,
N = Weight of Solute in gm. / Equivalent Weight × Volume in ltr.
The normality can be measured by using the value of Molarity of the solution. Therefore, the formula will be written as.
Normality (N) = Molarity × Molar mass / Equivalent mass
Normality (N) = Molarity × Basicity = Molarity × Acidity
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Relationship Between Normality and Molarity
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Basically the Normality and Molarity are two different terms but at some steps, they have a relation in between. Let's understand this. Normality is known as an equivalent concentration of the solution whereas Molarity is said to be the molar concentration of the solution.
Here,
Normality = Molarity × Molar Mass / Equivalent Mass
Normality for acids can be measured with the formula given below.
Normality = Molarity × Basicity
In order to obtain the basicity, first calculate the total number of H+ ions in the given acid molecule.
Now,
Normality = Molarity / Acidity
In case of acid, get or calculate the number of OH- ions that the base molecule gives during the process.
Difference between the Normality and Molarity
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The difference between normality and Molarity is given in tubular form.
| Normality | Molarity |
|---|---|
| Normality is the number of grams which is equivalent to the solute mixed in 1 liter of the solution. | Molarity is the total number of moles of solute present in 1 liter of the solution. |
| It is also termed as an equivalent concentration. | It is also known as molar concentration. |
| The process is used to find the gram equivalent in relation to the total volume of the solution. | This one is used to calculate the ratio between the number of moles in the total volume of the solution. |
| Formula: Normality = Gram Equivalent of Solute / Volume of Solution in liter | Formula: Molarity = number of moles of solute / Volume of solute in liters |
Things to Remember
- The concentration of a solution is the mass of solute mixed with the given amount of solution. This is called the concentration of a solution.
- Dilute solution is a solution which has a small quantity of solute.
- Whereas the concentrated solution is said to be a large amount of solute present in the solution.
- Molarity is defined as the number of moles of the solute dissolved or present in 1liter of the solution.
- Normality is defined as the number of grams that is equivalent to solute present in 1 liter of the solution.
- Molality is defined as the total number of moles of solute present in 1kilogram of the solvent. It is represented as 'm'.
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Sample Questions
Ques. Find out the normality of NaOH solution. The solution is produced by dissolving 0.2 gm NaOH to make a 250 ml solution. (3 marks)
Ans. Firstly, the formula of Normality is given by.
Normality (N) = No. of Gram Equivalent of solute / Volume of solution
No. of Gram Equivalent of the Solute = Weight / Equivalent weight
Now, Equivalent weight = Molar mass
= 23 + 16 + 1
Therefore, Equivalent weight = 40
Then, N = No. of gram of equivalent mass / Volume
= Weight / Equivalent weight × 1000 / Volume
= 2 / 40 × 1000 / 250 ( On dividing and multiplying the equation, we get)
= 0.2 N
Hence, The normality (N) for NaOH solution is 0.2 gm / ltr.
Ques. Find out the number of moles and molarity of Sulphuric acid having N/2 500 ml. of the given solution. (3 marks)
Ans. Calculate the no. of moles of H2SO4 first by using the formula,
N = n × M
½ = 2 × M
Therefore, No. of Moles = ¼
Then, Molarity of the given solution = No. of moles / Volume (liter)
¼ = n / 0.5
¼ = n × 10 / 5
5/4 = 10n
Now, n = 5 / 40
Hence, n = 1/8
Ques. Measure the equivalent weight of the given compound. (3 marks)
(a) NaCl
(b) Na2CO3
Ans. (a) Firstly calculate the molar mass of NaCl.
Sodium (Na) = 23 , Chloride (Cl) = 35.5
Add the molar mass together.
Now, Molar mass of NaCl = 23 + 35.5 = 58.5
Here, n = 1
Then, The Equivalent Weight = Molar mass / n
Therefore, Equivalent weight of NaCl = 58.5 / 1 = 58.5
(b) Na2CO3, At first calculate the molar mass.
Molar mass of Na2CO3 = 106
Then, n = 2 ( Because the Sodium salt ionizes to produce 2 Na+ and CO32– and the produced charge will be positive i.e. 2.)
Now, Equivalent weight = Molar mass / n
Hence, Equivalent weight of Na2CO3 = 106 / 2 = 53
Ques. Find out the normality of an acid if 21.18 mL is used to titrate around 0.1369 g of Na2CO3? (3 marks)
Ans. To find out the normality of an acid. Substituting the values in Normality formula we get
0.1369 g Na2CO3 × (1 mol/105.99 g) × (2 eq/1 mol) × (1 eq acid/1 eq base):
Solving the equation
= 2.583 × 10-3 eq acid / 0.02118 L = 0.1212 N
Hence, the Normality of an acid = 0.1212 N.
Ques. State the difference between normality and molarity. (3 marks)
Ans.The difference between Normality and Morality is given below.
- Normality is a quantitative measure in chemistry. It is considered as the number equivalent grams which is dissolved per liter of the solution. Molarity is said as the number of moles of solute dissolved per liter of solution.
- Normality is used to measure the gram equivalent to the total volume of the given solution whereas Molarity is used to identify the no. of moles in the total volume of the given solution.
Ques. What is the concentration of a solution? (2 marks)
Ans. The concentration of any solution is a way of expressing the amount of solute that is mixed with the given amount of solvent or solution. There is a big amount of dissolved solute in the given concentrated solution. Whereas the dilute solution has a small amount of dissolved solute.
Ques. Find the normality of 0.321 g sodium carbonate when it mixes with 250 ml of a solution? (3 marks)
Ans. To find out the normality first we have to write the formula of sodium carbonate. After writing the formula, we can get two sodium ions present in the solution for every carbonate ion. Now after solving the problem
N of 0.321 g of Sodium carbonate
The molecular formula of Sodium carbonate is Na2CO3.
N = Na2CO3 × 1 mol/105.99g × 2eq /1 mol
N = 0.1886 eq / 0.2500 L
N = 0.0755 N
Hence the normality of 0.321g of Sodium Carbonate is 0.0755.
Ques. What do you mean by Molarity? (2 marks)
Ans. Molarity is said as the number of moles of a solute present per liter of the solution. It is represented as 'M'. Molarity is also termed as the molar concentration of a solution. The SI unit for Molarity is given by mol/liter. Here per mole is referred to 1 mole of the solution.
Ques. What is Normality? State the SI unit, uses and limitations of Normality. (2 marks)
Ans. Normality is a term used to measure the concentration of the given solution. It is considered as the number of grams which is equivalent to the solute dissolved per/ liter of the solution. This is called Normality. It is denoted by 'N'. The SI unit used for this is gram / liter.
Ques. A solution of 200 mL is mixed with the Caustic Soda of 4 gm. Find the molarity of the Soda. (3 marks)
Ans. Given,
Mass of solute of Caustic Soda = 4gm
Volume of solution = 200 mL = 0.2 L
Formula of Molarity = Number of moles of solute / Volume of the Solution
Molar mass of Caustic Soda (Solute) = 23 g × 1 + 16 g × 1 + 1 g × 1
= ( 23 + 16 + 1 ) g
Now, No. of moles of solute = Given mass / Molecular mass
= 4 g / 40 g
= 0.1 g
Then, Molarity = No. of moles of solute / Volume of the Solution
= 0.1 / 0.2
= 0.5 M
Hence, the Molarity of Caustic Soda is 0.5 M.
Ques. A solution of 200 mL is mixed with the Caustic Soda of 5g. (3 marks)
Ans. The uses of Normality are given below.
- Normality is a process used to determine the level of concentration of the solution.
- It is used in precipitation reactions mainly to calculate the number of ions after the reaction happens.
- Normality is also used in redox reactions. Redox means to reduce. The number of electrons are measured during the process.
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