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.