Weekly Math Problem! #40

Molality. You weren't expecting that were you? Yeah...me either. 🤷🏿‍♀️😆 I wanted to post a calculus problem this week but, a conversation I had with one of my god-daughters (a college freshman) this evening, prompted me to post something different. I'm always interested in where mathematics shows up in the world and in other disciplines. So, this week we're putting our math skills to use in chemistry by doing a molality calculation. 

To solve this week's problem in completion, you need to recall the following math skills:

        ✔️     How to do substitution
        ✔️     How to do unit conversions
        ✔️     How to do metric conversions

You will also need the following chemistry skills:

        ✔️     How to use the periodic table
        ✔️     How to find molar mass
        ✔️     How to find moles of a compound

We'll definitely be looking up some things this week. WMP! #40 says:

Happy solving!

Check back on Friday, March 5th for the solution, which will be posted below ⬇️.

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✏️📓 Solution Time! 📓✏️

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Now, I've done Chemistry in college but it's been quite a few years since the last time I've done it. Nonetheless, the problem type is still familiar to me. Hopefully some of the resources I linked above were helpful. So...let's go! 💃🏿

Step 1. Calculate Molar Mass of the Solute

This is where you need to use the periodic table. You can't calculate the molality without knowing how many moles of the solute you have and you can't know how many moles of the solute you have without knowing the molar mass of the solute. Locate the elements of the solute (the thing being dissolved in water) in the periodic table to find what the mass of each is. Then proceed with the calculation as follows:

Step 2. Calculate Moles of Solute 

Now that we know the molar mass of NaCl, we can compute how many moles of the solute are present in 14.3 g of the substance. 

Step 3. Convert the Solvent to kg 

For whatever reason, the unit for the solvent (the things being dissolved into) is kg. Since our solvent is presented in g, we need to make the adjustment.

Step 4. Calculate the Molality of the Solution 

Here's the final step! 😄 Use the resulting information from steps 2 and 3 to calculate the molality.

Hmmm...not too bad. Now you know I just had to check my work--a way to ease the anxiety stemming from not having done this in years and to make sure I followed the steps properly. I used WolframAlpha to check my final answer: 

 

▪️ How did solving the problem this week go?

▪️ How did you feel about chemistry, in general?

▪️ Leave your response down below and let me know what you thought about this week's problem.

Thanks for solving with me this week!

Up next, WMP! #41.

Cheers!

The Younge Lady