**Problem Set**

How do we express the concentration of a solute in a solution? We use **Mass Percentage**.

Mass Percentage is one of the way of representing the concentration of a solute in a solution. Mass percentage is calculated as the mass of a solvent divided by the total mass of the solution, multiplied by \(100\%\).

So it is easy to find out the formula:

\(\text{Mass Percentage }=\frac{m_{solute}}{m_{solution}}\times100\%\)

A \(200g\) beer contains \(20g\) alcohol. So, the mass percentage of alcohol in the beer is:

\(\frac{20g}{200g}\times100\%=10\%\).

Some other notes:

The mass percentage does not change with the temperature and air pressure.

There are other ways to express the concentration of a solute in a solution such as volume percentage, molality and amount-of substance concentration.

Some reference books express mass percentage as \(g/g\). However, try not to use that to prevent a confusion with Solubility.

Now, there is an example:

I want to dilute a \(50g\), \(98\%\) \(H_2SO_4\) to a \(20\%\) solution. How much water should I add in **grams** to do this?

Solution:

\(50g\) is the mass of solution.

\(98\%\) is the mass percentage before adding water.

\(20\%\) is the mass percentage after adding water.

Note that the mass of \(H_2SO_4\) does not change before and after the water added.

So, let the fixed mass of \(H_2SO_4\) be \(c\) and the mass of water should add be \(x\)

Before adding water,

\(\frac{c g}{50g}\times100\%=98\%\)

\(c=\frac{98}{100}\times50\)

After adding water,

\(\frac{c g}{(50+x)g}\times100\%=20\%\)

\(c=\frac{20}{100}\times(50+x)\)

Compare the two equations we have,

\(\frac{98}{100}\times50=\frac{20}{100}\times(50+x)\)

\(x=195g\)

So, the amount of water we should add is \(195g\).

No vote yet

1 vote

×

Problem Loading...

Note Loading...

Set Loading...

Easy Math Editor

`*italics*`

or`_italics_`

italics`**bold**`

or`__bold__`

boldNote: you must add a full line of space before and after lists for them to show up correctlyparagraph 1

paragraph 2

`[example link](https://brilliant.org)`

`> This is a quote`

Remember to wrap math in \( ... \) or \[ ... \] to ensure proper formatting.`2 \times 3`

`2^{34}`

`a_{i-1}`

`\frac{2}{3}`

`\sqrt{2}`

`\sum_{i=1}^3`

`\sin \theta`

`\boxed{123}`

## Comments

Sort by:

TopNewestI can't find any good image for this topic. If you found one, feel free to give me the link! For your information, I will not continue any notes involve solution such as molality, ideal solution, Raoult's Law etc. because this topics need the concept of mol. So, I will continue to those section after the idea of mol is presented. However, I will continue my chemistry notes in gas.

Log in to reply

Thanks for this note...Could you also start a series on

OrganicChemistry, if possible. Looking forward to your note on mole concept.Log in to reply

Oops, sorry I can't start Organic Chemistry because I am weak in that part.

Log in to reply

NICE POST!CAN YOU GIVE SOME NOTES ON EQUILIBRIUM.

Log in to reply

Ok but that may take some time, hope you can wait because now I am focusing on gases. :)

Log in to reply

What does \(20%\) solution mean?

Log in to reply

Sorry, it is 20%

Log in to reply

In this particular example, it means that the mass of \(H_2SO_4\) is \(20\)% of the mass of the solution.

Log in to reply