How to Prepare 50 mL of 95% Ethanol

Preparing 50 mL of 95% ethanol requires precise measurements and a clear understanding of dilution principles. This guide will walk you through the process, from selecting the appropriate materials to executing the preparation steps.

Materials Needed

95% ethanol Distilled water A graduated cylinder or pipette A mixing container like a beaker or flask

Dilution Calculation

The process involves diluting a higher concentration of ethanol, such as 100% ethanol, to achieve the desired concentration. The formula for dilution is:

C1 x V1 C2 x V2

Where:

C1 concentration of the stock solution (100% or 1.0) V1 volume of the stock solution needed C2 desired concentration (95% or 0.95) V2 final volume of the diluted solution (50 mL)

Rearranging the formula gives:

V1 (C2 x V2) / C1

Calculation Steps

To find V1 (the volume of 100% ethanol needed):

V1 (0.95 x 50 mL) / 1.0 47.5 mL

You will need 47.5 mL of 100% ethanol. To find the volume of water required:

V_{water} V2 - V1 50 mL - 47.5 mL 2.5 mL

Preparation Steps

Measure 47.5 mL of 100% ethanol using the graduated cylinder. Measure 2.5 mL of distilled water. In a mixing container, combine the 47.5 mL of ethanol with the 2.5 mL of distilled water. Stir gently to mix the solution thoroughly.

Always use appropriate safety precautions when handling ethanol, such as wearing gloves and working in a well-ventilated area. Label the container with the concentration and date of preparation.

Alternative Methods for 95% Ethanol

If you purchase industrial ethanol or use ethanol for laboratory purposes, the concentration is already 95% (v/v). In this case, simply measure out 50 mL of the commercial product, and you have the required 95% ethanol.

Measure 48 mL of 99% ethanol using the formula: 0.95 0.99X / 50 (from the given example).

Mix the ethanol with water until the final volume of 50 mL is achieved.

Alternatively, if you have 99% ethanol (around 100% by volume), use the general chemistry dilution formula:

M1V1 M2V2

For example, if you have 100 mL of a 100% stock solution, and you want 50 mL of a 95% solution:

V1 (95 x 50 mL) / 100 47.5 mL

Add 47.5 mL of the stock solution to a beaker, then dilute with water to reach a final volume of 50 mL.

By following these steps accurately, you can prepare the precise concentration of ethanol needed for various applications, ensuring both safety and reliability.