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# Help Zone

### Student Question

Hello!

I have a lab tomorrow and I have to write a protocol for the dissolution that I have to do, where I have to use a 50 ml volumetric flask and I have to make a concentrated solution of 0.08 g / ml of NaCl. First, how do I calculate the mass of NaCl? Then, can you give me some tips for writing my protocol ??

Thank you !!!

Science ## Explanations (1)

• Explanation from Alloprof  Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

Thank you for your question 😉

First, when you try to find an unknown value, you need to use the data provided to you to help you find the appropriate formula.

In your case, you know the volume of your solution and its concentration. As you are looking for the mass, you can use the following formula which contains these three variables, and isolate the mass:

$$C = \frac{m}{V} \Rightarrow m = C \times V$$

You can then replace the variables with their respective values ​​to find the mass!

As for the protocol, it often involves listing the steps of your manipulations in chronological order precisely enough that someone reading it will be able to reproduce the experience.

It is important to specify the measuring instruments as well as their capacity, for example "a 25 ml graduated cylinder".

Also, each step must start with an infinitive verb and must represent only one action.