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Learn what is molarity and molality and how solute and solvent are important for calculating molarity and molality of solutions.

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As we all know that a chemical solution comprises two main components; solute and solvent. In a chemical solution, the component present in the highest concentration is known as a solvent. On the other hand, the other components that are present in smaller concentrations are called solutes. Solutes could be solid, liquid, or gas.

However, to know about the exact concentration of a given solution, we use specific concentration units. Why cannot we use already available measurement units like volume or mass? Because these measurement units are too large for measuring tiny particles of solute and solvent.

Thus, to study the chemical solutions, we use a unit based on mole - MOLARITY & MOLALITY

To know about mole and calculations based on the mole, read our article How to find molar mass, formula mass, and percentage composition?

Molarity

Suppose you are provided with a solution whose total volume is one liter, and it possesses three moles of solute. We will say that the molarity of that solution is three.

Thus, molarity (also known as molar concentration) can be defined as the number of moles of solute present or dissolved in one liter of solution. Keep in mind that we are here considering the number of liters of total solution other than that of solvent. Mathematically, molarity can be represented such as

Molarity = number of moles of solute/liters of solution = mol/L

To represent the molarity, we use the unit moles/liter that is shown by the symbol "M." Thus, whenever we see a solution labeled as 2M NH ₄ Cl, we will read it as two molar solutions of ammonium chloride.

How to calculate the molarity of a solution?

Suppose you are provided with a solution of 500ml, which possesses 42.23g of NH ₄ Cl. To find the molarity of that solution, follow these steps.

1. What you know

The problem shows that the total mass of NH ₄Cl present in the solution is 42.23 g. Moreover, the total volume of the solution is also 500ml. From the compound formula, we can also measure the molar mass of NH ₄ CL, which is 53.50 g/mol.

To learn how to calculate molar mass from the formula of a compound, read our article on how to find out molar mass, formula mass, and percentage composition.

2. Convert the units

According to the formula of molarity (M=Moles/liters), we have to convert the volume of solution in liters and the mass of solute in moles such as

Change ml into liters

L = given mass in g/1000 = 500/0.5000
500 ml = 0.5000 L

Change mass into moles

Number of moles = 1 mole of solute/molar mass × given mas
Number of moles = 1 mol of NH ₄CL/53.50g NH ₄CL × 42.23g NH ₄CL = 0.7893 mol NH ₄ CL

Calculate the molarity

Molarity = number of moles of solute/liters of solution
Molarity = 0.7893moles/0.5000L = 1.579M

Thus, the molarity of the given solution is 1.579M.

Molality

The Molality of a solution is known as its molal concentration. We can define the molality of a solution as
"The number of moles of solute present in the total mass of solvent"
Remember that here, unlike molarity, we consider only the mass of solvent other than the entire solution. Moreover, we are taking the mass of the solvent in kilograms other than liters. Mathematically, molality can be represented as

Molality = number of moles of solute/mass of solvent in kilograms = moles/kg.

The unit of molality is moles/kg, which is represented by m.

How to Find the Molality of a Solution?

Suppose you are asked to find out the molality of a solution that possesses 225g of benzene, in which 0.5g of toluene has been dissolved. To find the morality of this solution, follow these steps.

1. What you know

The problem showing that you have
Solute(toluene) = 0.5g
Solvent(benzene) = 225g
Molar mass of toluene (C ₇H ₈) = 92 g/mol

To get the most exact and precise molar mass, you need to use online molar mass calculator.

2. Convert the units

According to the formula (moles/kg), we have to convert the mass of solute into the number of moles and mass of solvent from grams to kilograms.

Change mass into moles

Moles of toluene = Given mass of toluene/molar mass of toluene Moles of toluene = 0.5/92 = 0.054 moles

Change grams into kilograms

Kilograms = given mass in grams/1000 = 225/1000 = 0.225 kg

Calculate the molality

Molality = number of moles of solute/ mass of solvent in kg
M = 0.054 moles/ 0.225 kg = 0.24m

Thus, the molality of the given solution is 0.24m.

Bottom Line

Molarity and morality are often confused with each other. However, there are some major differences between both these parameters, such as

In molarity, we take the total volume of solution(in liters) into consideration. On the other hand, we only consider the mass(in grams) of solvent while calculating molality.

The unit of molarity is moles/liters, which is shown by "M." On the other hand, the unit of molality is moles/kg, which is shown by "m."

Molarity depends on temperature and pressure, while molality remains constant even in T and P changing conditions.

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How To Find Out The Molarity And Molality Of A Solution

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As we all know that a chemical solution comprises two main components; solute and solvent. In a chemical solution, the component present in the highest concentration is known as a solvent. On the other hand, the other components that are present in smaller concentrations are called solutes.

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Periodic Table, Its History And Why It Is Important

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Periodic Table, Its History And Why It Is Important

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Learn what is Periodic Table along with Periodic Table History & its importance

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Introduction to the Periodic Table

Up Till now, 118 elements are known to man - 94 of them found in nature while the remaining 24 are made within the laboratories. These elements are arranged in a tubular style according to their increasing atomic numbers within a table called the Periodic table.

However, it's not that the scientists put all the elements randomly to this table; instead, all the elements were arranged according to their periodic characteristics and atomic numbers.

Periodic table is also used for balancing chemical equations during a chemical reaction if you are doing it manually. However, if you are using balancing chemical equations calculator you will still need that periodic table for doing it correctly.

Related: Learn how to balance redox reaction in basic solution.

History of the Periodic Table

To arrange all the known elements with that much preciseness and accuracy, the scientists had to work hard for about a complete century. Since various scientists worked on this project of assembling elements, the table kept on changing its shape and size such as,

Lavoisier's Periodic Table

The first periodic table was structured by a French scientist Antonie Lavoisier in 1789. He grouped the elements into two main classes - Metals and Non-metals.

Related: Simple ways for balancing complex chemical equations.

Dobereiner's Periodic Table

After forty years of this periodic table, another scientist Johann Wolfang Dobereiner grouped the elements into three groups based on their similar chemical and physical properties. He called these three groups triads.

He also proposed that the elements of the middle group possess the properties average to that of the other two groups.

Related: Learn about endothermic and exhothermic reactions and the general chemical equation.

John Newlands Periodic Table

In 1860, after discovering the atomic mass, British scientist John Newlands arranged the known elements based on their increasing atomic masses.

After assembling all the elements in the table, he noticed that every group of eight elements showed similar properties. He named his finding the law of octaves. The only drawback of the Newlands periodic table was that it didn't possess any space for undetected elements.

Related: Learn the complete process of sodium reaction with chlorine and making of sodium chloride.

Mendeleev Periodic Table

In 1866, Russian scientist Dmitri Mendeleev removed these errors and left gaps for undiscovered elements. His periodic table was the closest form of today's periodic table.

However, he also arranges the elements based on their atomic masses. The surprising thing was that he even predicted the nature of an undiscovered element (eka-aluminum at that time) that was needed to fill the gap in the table. Use this tool for calculating atomic mass.

Afterward, an element was discovered possessing the same properties Mendeleev described before, and today, the world knows that element as Gallium.

However, his periodic table also contained some errors like controversial positions of some elements. That's why Mendeleev's periodic table was also rejected.

Related: Find what you need to know about synthesis reaction in chemistry.

Moseley's Modern Periodic Table

In 1913, Henry Moseley discovered subatomic particles and gave the concept of atomic number. After that, he arranged the elements according to their atomic numbers.

Moseley's periodic table was the answer to all the confusion, and this is the same periodic table we use today.

Related: Find out the complete process of a metal displacement reaction in an aqueous medium.

Basics of the Periodic Table

The periodic table is a kind of 8×17 grid that is being placed over two separate rows.

Each element is represented by its atomic symbols in the table. The atomic mass and the atomic number of each element are written beside its symbol.

As stated before, these elements are arranged according to the increasing atomic numbers. These atomic numbers increase from left to right, and we call these horizontal rows periods.

On the other hand, the vertical columns of the periodic table are called groups. Remember that all the elements enlisted in a single group possess similar properties.

There are seven groups and eighteen periods in the periodic table. Some of the groups and periods are also named specifically like alkali metals group (I), alkaline earth metals group (II), halogen group(XVII), and noble gases group (XVIII). Similarly, the last two periods are also called lanthanides and actinides.

Besides periods and groups, the periodic table is divided into four blocks (s,p,d,f) based on the location of the valence electron of an atom. For example, all the atoms of block s possess the valence electrons in subshell "s" and so on.

Related: What are gas laws and how these laws are used in the real life?

Why is the Periodic Table Important?

If we say that the periodic table is nothing but just a tubular symmetry of elements, we would be wrong. This table enables the scientists to do so many complicated things just in a glance, such as

1. Predict the nature of chemical reactions conducted by each element

2. Analyze reactivity of each element and order of reactivity

3. Understand how the chemical properties of all the elements are different periodically from each other

4. Assume the properties and nature of yet-to-discover elements.

5. Study the atomic structure of each element and check the similarities and dissimilarities among elements

6. Design the chemical reactions to get the desired cosmetic and pharmaceutical products.

On a final note, we can say that this periodic table of elements is not just a catalog or guide of the known elements; instead, it is a window that opens up to the entire universe and helps us understand the realm around us.

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What is Periodic Table and What is the Base of this Table

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Up Till now, 118 elements are known to man - 94 of them found in nature while the remaining 24 are made within the laboratories. These elements are arranged in a tubular style according to their increasing atomic numbers within a table called the Periodic table.