PLS HELP - URGENT - How salty?

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Student-5
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PLS HELP - URGENT - How salty?

Post by Student-5 »

plz help me! I need help on the science project "How Salty Does the Sea Have to Be for an Egg to Float?" and im stuck on the absolute mass concentration and relative salt concentrations. I have Looked everywhere for an answer and yet i cant seem to understand. Plz someone help fast i dont have too much time to complete this project!
audreyln
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Re: PLS HELP - URGENT - How salty?

Post by audreyln »

Hello,

This sounds like a fun project! Step 4, part g in the Experimental Procedure describes how to calculate the absolute mass concentrations using the formula that is in the Introduction section above.

The first thing you need to do is calculate the Concentration of Stock (this is what you mixed up in the big bowl with 1 cup salt and 5 cups water). This is the grams of salt (1 cup = 292 grams) divided by the liters of water (1 cup = 237 mL or 0.237 L so 5 cups = 1.185 L) so the Concentration of Stock equals 236.4 g/L. This is your absolute mass concentration for Cup 1.

Next you will need to calculate the absolute mass concentration or Concentration of Dilution of Cup 2. Cup 2 has 3/4 cup of stock (0.75 * 0.237 L = 0.17775 L) and 3/4 cup of water so the Total Volume of Dilution is (0.17775 L + 0.17775 L = 0.3555 L). So using the formula in the introduction section the Concentration of Dilution equals (236.4 g/L * 0.17775 L) / 0.3555 L = 118.2 g/L. This is your absolute mass concentration for Cup 2.

You will then repeat this last step with Cups 3-4. Except for the Cup 3 calculation the Concentration of Stock is no longer 236.4 it is now 118.2 g/L since the stock added was from Cup 2.

Once you have calculated the absolute mass concentrations of Cups 1-4 you can calculate the relative salt concentration. For Cup 2 this would be 118.2 g/L divided by 236.4 g/L = 0.5 or 50%. This says that Cup 2 has half of the salt that Cup 1 has. To calculate this for Cup 3 you would use your Cup 3 absolute mass concentration divided by 236.4 g/L.

Hope this helps with this tricky part of the project!

Audrey
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