Molarity - How to make Molar Solution

Molarity

The quantity of a solute dissolved in a certain volume of a solution is measured in molarity, which is represented by the letter "M". It is described as the quantity of solute in a solution measured in moles per litre. Molecules per litre (mol/L) or, in certain situations, moles per deciliter (mol/dL) are used to denote molarity.

A solution with a concentration described in terms of molarity (moles per litre) is referred to as a molar solution, also known as a molarity solution. It indicates that a certain number of moles of the solute are dissolved for each litre of the solution.

 The formula for calculating molarity is:

Molarity (M) = (moles of solute) / (volume of solution in liters)

This formula can be rearranged to solve for either moles of solute or volume of solution:

 

moles of solute = (Molarity) x (volume of solution in liters)

 

volume of solution in liters = (moles of solute) / (Molarity)

 

For example, if you have 0.5 moles of solute and you dissolve it in 2 liters of solution, the molarity would be:

Molarity = (0.5 moles) / (2 liters) = 0.25 M

Therefore, the molar solution would be a 0.25 M solution.

Molar Solution Preparation 

The process to make a molar solution involves the following steps:

1. Determine the desired concentration: 

Decide the molarity (concentration) you want to achieve for your solution. For example, if you want a 1 M solution, you would have 1 mole of solute per liter of solution.

2. Calculate the amount of solute needed: 

Determine the molecular weight (molar mass) of the solute you are using. This is the mass of the solute in grams per mole. Multiply the desired molarity by the desired volume in liters to obtain the number of moles of solute required.

3. Weigh the solute:

 Use an analytical balance to measure the calculated amount of the solute accurately. This is typically done using a weighing boat or a container.

4. Dissolve the solute: 

Transfer the weighed solute to a clean container, such as a beaker or a flask. Add a small amount of a suitable solvent (such as water) to dissolve the solute. Stir or swirl the mixture until the solute is completely dissolved.

5. Rinse and transfer: 

If necessary, rinse the container used for dissolving the solute to ensure no solute is left behind. Then, transfer the solution to a volumetric flask to ensure accurate measurement of the final volume.

6. Dilution (if needed): 

If the desired volume is different from the volume in the volumetric flask, you may have to dilute or concentrate the solution. To dilute, add the solvent (water) to reach the desired final volume while maintaining the desired molarity.

Remember to take appropriate safety precautions when handling chemicals and follow any specific guidelines or procedures provided by your instructor or chemical manufacturer.

How to measure molarity and how to make 2 Molar solution of NaOH?

To measure molarity, you need to determine the number of moles of solute (in this case, NaOH) present in a given volume of solution. Here's how you can do it:

1. Obtain the necessary materials: 

You will need NaOH, a balance, a graduated cylinder or volumetric flask, distilled water, and a stirring rod.

2. Calculate the required mass of NaOH: 

Determine the desired concentration and volume of the solution. In this case, we want to make a 2 M NaOH solution. Now, check the molar mass of NaOH, which is approximately 39.997 grams/mol. To calculate the mass of NaOH needed, use the formula mass = moles × molar mass. Since we want a 2 M NaOH solution, we know that 1 liter of the solution will contain 2 moles of NaOH. So the mass needed will be 2 moles × 39.997 g/mol = 79.994 grams.

3. Prepare the solution: 

Add the calculated mass of NaOH to a clean container (graduated cylinder or volumetric flask is recommended). Measure out the exact volume of distilled water needed. For a 2 M solution, aim for a final volume of 1 liter. Dissolve the NaOH completely by stirring the mixture.

4. Adjust Volume: 

If the volume is not exactly 1 liter, add distilled water to increase or decrease the volume until you reach the desired volume (1 liter in this case). Stir the solution thoroughly to ensure complete mixing.

It is important to note that NaOH is a strong base and can be corrosive; therefore, handle it with caution, wear appropriate protective equipment, and follow all safety protocols.

How to prepare 2 Molar NaOH solution in 50ml water?

By using above formula we can calculate the amount of NaOH required to dissolved in 50ml water. 

Molarity =2M

Volume in ml =50ml

Weight of NaOH =?

 

Molarity = mass of solute / molar mass of solute ×1000/volume of solution in ml

So, 

Put value in the given formula 

2= x/40×1000/50

x= 0.25 g

Here, we take 0.25 g of NaOH by using weight balance then add it into beaker then add 50 ml water in it, it will be 2M solution of NaOH in 50ml water. 

 

Dilution of Concentrated 

solutions 

To dilute a solution in terms of molarity, you need to add more solvent to decrease the concentration of the solute.

The basic formula for dilution is:

M1V1 = M2V2

Where:

M1 = Initial molarity of the solution

V1 = Initial volume of the solution

M2 = Final molarity of the solution

V2 = Final volume of the solution

To calculate the final volume or molarity, rearrange the formula as needed.

Example:

Let's say you have 200 mL of a 0.5 M solution and dilute it to a final concentration of 0.2 M. To find the final volume, use the following formula:

M1V1 = M2V2

(0.5 M) * (200 mL) = (0.2 M) * (V2)

Solving for V2:

V2 = (0.5 M * 200 mL) / (0.2 M) = 500 mL

 

Therefore, to dilute the solution from 0.5 M to 0.2 M, we add 300 mL of solvent (diluent) to make a final volume of 500 mL.

 

Solution and their Types

Solutions and Types of Solutions

Solution 

 A solution is a homogeneous mixture composed of two or more substances, where the solute is uniformly dispersed in the solvent. While solutions are often thought of as liquid mixtures, they can also exist in solid and gas phases. In the case of a solid solution, the solute particles are distributed evenly throughout the solid solvent, resulting in a uniform structure.

Components of Solution 

In a solution, there are typically two main components: the solute and the solvent.

Solute

The solute refers to the substance that is being dissolved in the solution. It is the component that is present in a lesser amount. For example, when salt is dissolved in water, salt is the solute.

Solvent

On the other side, the material that dissolves is known as a solvent. It is the element that is more abundantly present. Water serves as the solvent in the salt and water illustration.

When the solute and solvent contact, they combine to create a homogenous mixture in which the solute particles are evenly distributed throughout the solvent. Atoms, ions, molecules, and even other substances can make up the solute particles.

The fact that the solute and solvent may exist in several physical states is significant. For instance, the solvent may be a liquid or a gas, whereas the solute may be a solid. As an alternative, the solute and solvent may both be in the same state of matter, such as being liquids.

Understanding the components of a solution, particularly the solute and solvent, is crucial for determining the properties and behavior of the solution, as well as for various applications in fields like chemistry, biology, and engineering.

Solution

Solid Solutions

An alloy is a perfect example of a solid solution. It is a mixture of two or more metals, or a metal combined with a non-metal. The solute within the alloy is typically a metal that is added in small amounts to the solvent metal. The solvent metal determines the majority of the properties and characteristics of the alloy.

For instance, when copper (Cu) is mixed with nickel (Ni) in appropriate ratios, it forms an alloy known as cupronickel. The copper acts as the solvent, and the nickel is the solute. The solute nickel atoms blend within the copper lattice, creating a uniform solid solution. The resulting cupronickel alloy exhibits enhanced resistance to corrosion and is commonly used in marine applications, such as for making coins, pipes, and marine equipment.

Another example is alloy steel, which is created by combining iron (Fe) with tiny quantities of carbon (C). The iron serves as a solvent, dispersing the carbon atoms throughout the iron lattice to create a solid solution. The resultant alloy steel has enhanced mechanical characteristics, including greater strength and hardness, which makes it perfect for use in a variety of industries, including construction, tool production, and vehicle components.

In conclusion, alloys are solid solutions made up of one or more solute elements and a solvent metal or non-metal. A homogeneous solid solution with distinct features and characteristics is produced by the uniform dispersion of the solute atoms inside the solvent lattice. In addition to solid solutions, solutions can also exist in liquid and gas phases, where the solute is uniformly dispersed in the solvent.

Liquid Solutions 

A liquid solution is formed when a liquid solvent dissolves one or more solute substances. For example, when sugar (solute) is added to water (solvent), it dissolves and forms a homogeneous liquid solution known as a sugar solution. The sugar molecules become uniformly dispersed throughout the water, resulting in a clear and homogeneous mixture.

Gas Solutions 

Similarly, gas solutions occur when a gas dissolves into another gas or a liquid. An example of a gas solution is the dissolution of carbon dioxide (CO2) in water. When carbon dioxide gas is exposed to water, it dissolves and forms carbonic acid, resulting in a gas-liquid solution. The dissolved carbon dioxide molecules are evenly distributed throughout the water.

When one gas dissolves in another gas, a gas solution can also result. For instance, when oxygen (O2) and nitrogen (N2) gases are combined, the individual gas molecules become equally scattered in one another, resulting in the formation of a gaseous solution. A common example of a gaseous solution is air, which is a mixture of several gases including oxygen, nitrogen, carbon dioxide, and others.

The solute particles are equally dispersed throughout the solvent phase in both liquid and gaseous solutions, creating a homogenous combination. This makes it possible for the solute materials to be quickly combined with the solvent and transported, supporting a number of critical activities such chemical reactions, biological processes, and physical transformations. 

Types of Solutions

There are several types of solutions based on the solute, solvent, and concentration. Some of the common types include:

1. Homogeneous Solution:

 In this type of solution, the solute particles are uniformly distributed and dissolved in the solvent. The solute particles are not visible to the naked eye, and the solution appears to be a single phase. For example, a mixture of salt and water.

2. Heterogeneous Solution:

 This type of solution contains visible particles of the solute that do not completely dissolve in the solvent. The solute particles are not uniformly distributed, and the solution appears to have multiple phases or layers. For example, a mixture of oil and water.

3. Dilute Solution: 

A dilute solution contains a small amount of solute dissolved in a large amount of solvent. The concentration of the solute is relatively low.

4. Concentrated Solution: 

A concentrated solution contains a large amount of solute dissolved in a smaller amount of solvent. The concentration of the solute is relatively high.

5. Unsaturated Solution: 

An unsaturated solution contains a smaller amount of solute than the maximum amount that can be dissolved in a given amount of solvent at a particular temperature. It has the capacity to dissolve more solute.

6. Saturated Solution: 

A saturated solution contains the maximum amount of solute that can be dissolved in a given amount of solvent at a particular temperature. It is in a state of equilibrium where the rate of dissolution equals the rate of crystallization.

Saturated Solution

7. Supersaturated Solution: 

A supersaturated solution contains more solute than what can normally dissolve in a given amount of solvent at a particular temperature. The solution is temporarily stable but can become unstable and precipitate if disturbed or if a seed crystal is added.

8. Aqueous Solution 

A form of solution called an aqueous solution uses water as its solvent. It is identified by the sign "(aq)" following the solute's chemical formula. In aqueous solutions, several chemical and biological activities take place. For instance, a hydrochloric acid solution (HCl(aq)) is created when hydrochloric acid (HCl) is dissolved in water. Similar to this, a sodium hydroxide solution (NaOH(aq)) is created when sodium hydroxide (NaOH) is dissolved in water. Water serves as the solvent in both scenarios, and the solute molecules are evenly dispersed in the aqueous solution.

Concentration Units-Mass Percent (%)

Concentration

The term "concentration" describes how much solute is contained in a specific volume of solvent or solution. It measures a substance's relative density or abundance within the mixture.

Making precise volume solutions, usually referred to as percent solutions, is the main application for a volumetric flask. It is specially made to deliver an accurate volume measurement with a small margin of error, often at a set volume. On the other hand, a volumetric flask offers more precision than a measuring cylinder, despite the latter's usage for volume measurements.

Units of Concentration

There are several units commonly used to measure concentration, depending on the nature of the mixture and the properties of the substances involved. Here are some commonly used units of concentration:

1. Molarity (M): 

Molarity measures the number of moles of solute present or dissolved in one liter of solution. It is expressed as moles per liter (mol/L or M). For example, a solution with a molarity of 0.22 M means that there are 0.222 moles of solute dissolved in every liter of solution.

2. Mass Percent (%): 

Mass percent represents the percentage of the mass of the solute in a solution. It is calculated by dividing the mass of the solute by the mass of the solution and multiplying by 100%. Mass percent is denoted by the symbol "%". For example, a mass percent of 20% means that 20 grams of solute are present in 100 grams of solution.

3. Molality (m): 

Molality measures the concentration of a solute in terms of its moles per kilogram of solvent. It is expressed as moles per kilogram (mol/kg). Molality is particularly useful when the volume of the solution changes with temperature, as it is not affected by changes in volume.

4. Normality (N): 

Normality is a measure of concentration that considers the equivalent weights of solute species involved in a chemical reaction. It is expressed in equivalents per liter (eq/L or N).

5. Parts Per Million (ppm) or Parts Per Billion (ppb): 

These units are used when dealing with extremely dilute solutions. PPM and PPB indicate the number of parts of the solute in one million or one billion parts of the solution, respectively.

These are just a few examples of the units used to measure concentration, and there may be specific units used for different properties or industries. It is important to use the appropriate unit for the specific context or calculation at hand.

 

 Here we will discuss mass percent with complete details.

Mass Percent (%) Solution 

To make percent solutions, we need to understand the different ways in which the percentage is calculated: m/m (mass/mass), m/v (mass/volume), v/m (volume/mass), and v/v (volume/volume).

 

1. m/m (mass/mass): 

This means the mass of the solute is expressed as a percentage of the total mass of the solution.

  To make a m/m percent solution, you need to weigh the solute (in grams) and the total solution (including the solute) to calculate the mass percentage.

 

% m/m = (mass of solute / mass of solution) x 100

 

Point To Remember 

In a mass-by-mass percent solution, we must weigh both the solute and the solution. A weight balance must be used in order to precisely calculate the solution's mass. The entire mass of the solution may not be precisely measured with a measuring flask alone. Instead of measuring masses, a measuring flask is often used to measure volumes.

We can precisely determine the % concentration by using a weight balance to measure the mass of the solution in question. This makes sure that the right ratios of solute and solvent are employed to get the concentration you want. Therefore, while producing a mass-by-mass percent solution, it is advised to use a weight balance to determine the mass of the solution.

2. m/v (mass/volume): 

This means the mass of the solute is expressed as a percentage of the total volume of the solution.

   - To make a m/v percent solution, you need to weigh the solute (in grams) and measure the volume of the solution (in milliliters) to calculate the mass/volume percentage.

 

% m/v = (mass of solute / volume of solution) x 100

 

3. v/m (volume/mass): 

This means the volume of the solute is expressed as a percentage of the total mass of the solution.

To make a v/m percent solution, we first measure the volume of the solute (in milliliters) and weigh the total solution (including the solute) to calculate the volume/mass percentage.

 

     % v/m = (volume of solute / mass of solution) x 100

 

It is necessary to use a weight balance for m/m (mass/mass) and v/m (volume/mass) percent solutions. In both cases, we need to measure the mass of the solute, and for v/m solutions, we also need to measure the mass of the solution.

Using a weight balance ensures accurate measurements of the mass, which is crucial for calculating the percentage accurately. It is recommended to use a precision balance that can measure small masses with high accuracy for precise results.

However, for m/v (mass/volume) and v/v (volume/volume) percent solutions, we don't necessarily need a weight balance. For m/v solutions, we only need to measure the mass of the solute and the volume of the solution. For v/v solutions, we need to note or measure the volume of both the solute and the solution. In these cases, we can use a graduated cylinder or a volumetric flask with appropriate markings to measure the volume accurately.

 

4. v/v (volume/volume):

 This means the volume of the solute is expressed as a percentage of the total volume of the solution.

To prepare a v/v percent solution, we first need to measure the volume of the solute (in milliliters) and the volume of the solution (in milliliters) to calculate the volume/volume percentage.

 

   % v/v = (volume of solute / volume of solution) x 100

 

In each case, after calculating the percentage, one can add the solute to the solvent and mix thoroughly to create the percent solution.

 

Important Terms In Surface Chemistry

Surface Chemistry 

 

Surface Chemistry 

Surface chemistry refers to the study of chemical processes that occur at the surfaces or interfaces of materials, such as solids, liquids, or gases. This includes phenomena such as adsorption, desorption, catalysis, corrosion, and oxidation that happen at the boundary between two phases.

Importance:

As a result of the critical roles that surface and interface play in several applications, such as catalysis (chemical reactions), corrosion of materials, electrochemistry, adhesion, lubrication, heterogeneous mixture, and purification procedures, among others, surface chemistry is significant in the field of chemistry. Scientists can create novel materials with desired features and enhance the effectiveness of many industrial processes by better understanding the mechanics and characteristics of surface chemistry. To create efficient products and procedures, many sectors, including biotechnology, electronics, medicine, energy, chemical manufacture, and environmental cleanup, rely on a thorough grasp of surface chemistry fundamentals.

Absorption:

Phenomena of absorption involve the transfer of matter or energy from an external medium into another medium. For example, in the process of absorption, a substance (the adsorbate) is transferred from one fluid or solid phase into another (the adsorbent), often resulting in the adsorbate being held or bound onto the surface of the adsorbent. This process can be influenced by various factors including temperature, pressure, time, surface area, and the physical and chemical properties of the adsorbate and adsorbent.

Types of Absorption:

There are various types of absorption, including:

A. Physical absorption:

This is the reversible process of gases and vapors being taken up into or adsorbed onto the surface of a solid or liquid.

B. Chemical absorption:

This is a process where a substance reacts with a solute to form a new compound. 

C. Molecular absorption: 

This is the process where the energy of a photon or radiant energy is absorbed by a molecule, leading to an increase in its internal energy.

D. Biological absorption:

This is the process by which living organisms absorb nutrients and other materials in order to carry out their metabolic functions. 

E. Sound absorption: 

This is the process where sound waves are absorbed by a material and converted into heat or other forms of energy.

Adsorbate and Adsorbent:

Adsorbate refers to the substance being adsorbed, while adsorbent refers to the material on which the adsorption occurs. 

Desorption:

Desorption is the process in which an adsorbed substance is released from an adsorbent material. It can occur naturally or be induced through external stimuli (e.g., heating). 

Sorption:

Sorption is a general term that refers to both adsorption and desorption, the process of attachment and detachment of molecules onto materials. 

Adsorption Isotherm:

Adsorption isotherm refers to the relationship between the amount of a gas or liquid adsorbed onto a solid surface and its equilibrium pressure or concentration. There are several types of absorption isotherms which are commonly used in surface chemistry research. These include:

A. Langmuir Isotherm: 

This is one of the most commonly used isotherms to describe adsorption of a gas onto a solid surface. It assumes that there are a limited number of adsorption sites on the surface of the solid, and that the adsorption of gas molecules onto these sites follows an equilibrium process. The Langmuir equation is expressed as Q = QmKc / (1 + Kc), where Q is the amount of adsorbate on the surface, Qm is the maximum amount that can be adsorbed and Kc is a constant related to the affinity of the adsorbate for the surface.

B. Freundlich Isotherm: 

The Freundlich isotherm is often used for heterogeneous surfaces where there is no specific adsorption site. It assumes that there is a certain degree of adsorption on all surface areas. This isotherm is expressed as Q = Kc^(1/n), where Q is the amount of adsorbate on the surface, K and n are constants related to the surface properties, and c is the concentration of adsorbate.

Overall, these absorption isotherms are essential in understanding how molecules are adsorbed on the surface of various materials, which contributes to the development of new materials and improved industrial processes.

Catalysis: 

Catalysis is a process in which a substance accelerates a chemical reaction without itself being consumed or changed. In surface chemistry, catalysis is the study of the surfaces of catalysts and the way they interact with reactant molecules to increase the rate of chemical reactions.

Colloids: 

Colloids are systems in which small particles are dispersed in a continuous medium. These particles are typically bigger than individual atoms or molecules but smaller than visible particles. Examples of colloids include milk, blood, and fog. In surface chemistry, the study of colloids includes the behavior of particles at interfaces and the effects of surface chemistry on the stability and properties of colloidal dispersions.

Emulsion: 

The act of combining two immiscible liquids—typically, oil and water—to create an emulsion results in a stable composition. An emulsion is the end product, and it can be either an oil-in-water (O/W) or a water-in-oil (W/O) emulsion. The concepts of surface tension, interfacial tension, and the adsorption of surfactants and stabilizing agents at the interfaces of emulsifying systems are all included in the study of emulsions in surface chemistry.

For Complete details 

Emulsions, Adsorption and Adsorption Isotherm 

Factors Affecting Boiling Point and Vapour Pressure of Liquid

Boiling Point 

The boiling point is the temperature at which a liquid turns into a gas or the point where the vapor pressure of a liquid equals the atmospheric pressure. For example, Water has the chemical formula H2O and is an inorganic substance. It is a translucent, tasteless, odorless, and almost colorless chemical substance that is the primary ingredient of the hydrosphere of Earth and all known living creatures' fluids. At 1 atm (i.e., 101.325 kPa), the typical boiling point is 99.97 °C (211.9 °F). At a standard pressure of 100 kPa (1 bar), the IUPAC-recommended standardized boiling point of water is 99.61 °C (211.3 °F).

 The factors that affect boiling point include:

Factors:
1. Atmospheric pressure: 

The higher the atmospheric pressure, the higher the boiling point. This is because more pressure is required to keep the liquid in a liquid state at a higher temperature.

2. Intermolecular forces: 

The stronger the intermolecular forces of attraction between the molecules of a substance, the higher the boiling point. The reason is that more energy is required to overcome these forces and break the bonds between the molecules.

3. Molecular weight: 

Generally, the higher the molecular weight of a substance, the higher the boiling point. This is because more energy is required to overcome the stronger intermolecular forces between larger molecules.

4. Presence of impurities: 

The presence of impurities in a substance can lower its boiling point. This is because impurities disrupt the intermolecular forces between the molecules, making it easier to convert the liquid into a gas.

• 

  Factors Affecting Boiling Point 

Vapour Pressure 

Vapor pressure is defined as the pressure exerted by the vapor of a substance in a closed system when it is in equilibrium with its liquid or solid phase at a particular temperature. In simpler terms, it is the measure of the tendency of molecules in a liquid to escape into the atmosphere as a gas or vapor. As an example, when water vapor molecules are gaseous, they exert pressure on the surrounding environment. Water has a vapor pressure of 23.8 mmHg at 298K. 

Factors:
There are several factors that affect vapor pressure, including:

1. Temperature: 

Vapor pressure increases with an increase in temperature. This is because at higher temperatures, more molecules have sufficient kinetic energy to escape from the liquid and become a vapor.

2. Intermolecular forces: 

The strength of intermolecular forces between molecules affects vapor pressure. Stronger forces lead to lower vapor pressure as molecules are more tightly held in the liquid phase.

3. Molecular weight: 

The higher the molecular weight of a substance, the lower the vapor pressure. This is because heavier molecules have weaker kinetic energy and are less likely to escape the liquid phase.

4. Surface area: 

An increase in surface area leads to an increase in vapor pressure. This is because more molecules are available to escape into the atmosphere, increasing the likelihood of vaporization.

5. Presence of other gases: 

The presence of other gases can affect vapor pressure. If the gas is less dense than air, it will tend to rise and decrease the pressure at the surface of the liquid, leading to an increase in vapor pressure.

• 

  Factors Affecting Vapor Pressure of Liquid 

Example:

An example of the relationship between boiling point and vapor pressure is the difference between water and acetone. The boiling point of water is 100℃, while the boiling point of acetone is much lower at 56℃. This indicates that acetone has a much higher vapor pressure at room temperature than water.

This is because acetone molecules have weaker intermolecular forces than water molecules, meaning that more of them can escape into the atmosphere at a given temperature. As a result, acetone evaporates more quickly than water and has a higher vapor pressure.

In contrast, water has stronger intermolecular forces and a higher boiling point, which makes it less likely to evaporate at room temperature. This is why water is a liquid at room temperature, while acetone is a volatile liquid that easily evaporates.