# How do you calculate molality from molarity?

See explanation.

If all you are given is , then you also need to know the of the solution to calculate , m (mol/kg solvent).

The easiest way to understand the process is to assume you have 1L of solution which is 1000 mL. Think of the units of molarity and molality. So here is an example:

What is the molality of a ##”3.00 M”## solution of ##”NaCl”##? The density of the solution is ##”1.12 g/mL”##.

We know that in ##”1.00 L”## of solution, there are ##3.00## mol of ##”NaCl”##, since that is the meaning of ##”3.00 M”##.

If we figure out how many kg of water there are in ##”1.00 L”## of this solution, we are almost done! Many students are confused between solution and , so be careful.

First let’s figure out the mass of the solution using dimensional analysis and density:

##”? g soln” = 1.00 cancel(“L”) xx (1000 cancel(“mL”))/(1 cancel(“L”)) xx (“1.12 g”)/(1 cancel(“mL”)) = “1120 g solution”##

Now we need to know the mass of just the water.

##”? g water” = “mass of the solution” – “mass of NaCl in the solution”##

##= “1120 g soln” – (3.00 cancel(“mol NaCl”) xx “58.4 g”/cancel(“1 mol NaCl”))##

##= “1120 g soln” – “175 g NaCl” = “945 g water”##

## = “0.945 kg of water”##

Now, use the units of molality as an equation:

##”molality” (“mol solute”https://studydaddy.com/”kg solvent”) = (“no. moles NaCl”)/(“no. kg water”)##

So,

##”molality” = (“3.00 mol NaCl”)/(“0.945 kg water”) = “3.17 m NaCl”##

## Calculate the price of your order

550 words
We'll send you the first draft for approval by September 11, 2018 at 10:52 AM
Total price:
\$26
The price is based on these factors:
Number of pages
Urgency
Basic features
• Free title page and bibliography
• Unlimited revisions
• Plagiarism-free guarantee
• Money-back guarantee
On-demand options
• Writer’s samples
• Part-by-part delivery
• Overnight delivery
• Copies of used sources
Paper format
• 275 words per page
• 12 pt Arial/Times New Roman
• Double line spacing
• Any citation style (APA, MLA, Chicago/Turabian, Harvard)

# Our guarantees

Delivering a high-quality product at a reasonable price is not enough anymore.
That’s why we have developed 5 beneficial guarantees that will make your experience with our service enjoyable, easy, and safe.

### Money-back guarantee

You have to be 100% sure of the quality of your product to give a money-back guarantee. This describes us perfectly. Make sure that this guarantee is totally transparent.

### Zero-plagiarism guarantee

Each paper is composed from scratch, according to your instructions. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in.

### Free-revision policy

Thanks to our free revisions, there is no way for you to be unsatisfied. We will work on your paper until you are completely happy with the result.