In this article, I’ll tell you from where to start in the lab. When you enter in the laboratory, the most important thing you must know is ” calculation in biotechnology.”

As,

##### Correct reagent is directly proportional to the correct result

In this article, you’ll only get two formulas that are useful in the labs. Normally in labs we have either solid chemicals or liquid stock.we have to make the desired concentration of the solution from solid or liquid stock,

## Calculation in Biotechnology

The basic formula that I’m using for molarity calculation is

**W** – Weight of the reagent required **( in grams)**

**M** – Molarity required

**MW** – Molecular weight of the reagent

**V** – final volume of solution required** (in liters)**

# W_{(in grams)} = M_{(in moles)} x MW x V_{(in liters)}

_{(in grams)}

_{(in liters)}

for example,

#### How are 500 mL of 0.3 M NaCl prepared?

NaCl is solid, so we use above formula to calculate the weight of the NaCl required to make 500 ml of 0.3 M NaCl solution.

Given,

**M** = Molarity of the solution required = **0.3 M**

**MW** = Molecular weight of the NaCl = **40 g/mol**

**V** = Volume of solution to be preapared =**500 ml** = **0.5 L** (as volume** must be in liters**)

**W** = Weight of the NaCl required.( In grams)

calculation part,

### W = M X MW X V

= 0.3 X 40 X 0.5

= 0.6 grms or 600 mg

so, 600 mg or 0.6 grams of NaCl is 500ml of water (final volume) to make its concentration to 0.3 M.

in second case when we have to reduce the concentration of stock.

example – From the above stock (500 ml of NaCl ,0.3 M) we have to make 500 ml of 0.2M NaCl ?

Method to be used,

# C_{1}V_{1} = C_{2}V_{2}

- V
_{1}= Volume of stock solution needed to make the new solution**(Unknown)** - C
_{1}= Concentration of stock solution**(Here 0.3 M)** - V
_{2}= Final volume of new solution**(Given – 500 ml)** - C
_{2}= Final concentration of new solution**(Given – 0.2M)**

It’s important to use same units for concentration and volume on both sides.

V1 = (C_{2}V2) / C_{1}

= (0.2 X 500 ) / 0.3

= 333.33 ml

to make 500 ml of 0.2 M NaCl from 0.3 M stock, we have to measure 333.33 mL of stock and make its final volume to 500 ml.