# Solutions:- Part 2 – Preparation of solutions (Molar, Normal) and Dilution

- These are the formulas for the preparation of various solutions.
- Elaborated with examples.

**Molar solution**

- It contains one mole of solute in a solution making equal to one liter.
- Molar solution = Molecular weight in gram / liter in the solution.
- Example: I molar solution of sodium chloride (NaCl).

Sodium atomic weight = 23

Chloride atomic weight = 35.5

Total molecular weight = 58.5 gram / mol

Now dissolve 58.5 grams of NaCl in distilled water and make the solution to one liter.

#### Normal solution

- The normal solution is defined as the gram equivalent weight per liter of the solution.
- Normal solution = gram equivalent weight of solute/liter of the solution.

- These solutions are expressed as N.
- Gram equivalent weight = molecular weight/valency

#### Example

**To make 1 N sodium chloride solution**

- The molecular weight of NaCl is 58.5
- Gram equivalent weight of NaCl = molecular weight / 1 (valency)
- So dissolve 58.5 grams of NaCl in distilled water and makeup to one liter.

#### Percent solution

- This is per hundred part of the total solution.
- There are three possibilities of a percent solution.
- Weight/weight is this a percentage of solute in 100 grams of final solution equal to solute + solvent.
- e.g. 5 grams of NaCl dissolved in 95 grams of water which is around 95 mL.

- Weight/volume e.g. 5 grams of NaCl dissolved in water and the volume is made 100 ml is called a 5% solution of NaCl.
- Volume/volume composed of two solutions. e.g. if we take 5 mL of acid and dilute to 100 mL of water will be a 5% solution of that acid.

- Weight/weight is this a percentage of solute in 100 grams of final solution equal to solute + solvent.

#### Dilution

- This procedure is very common to prepare the dilution of the serum where there is a high concentration of chemicals like urea in blood if it is above 300 mg/dL.
- If we make a dilution of serum like this:
- Serum = 1 ml
- Diluting fluid 4 mL
- This will be a dilution of 1:5 (1+4 =5).