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Warmup 10/20/14

Warmup 10/20/14. Let's say you make some chocolate milk one day. You try it and it's REALLY good. You want to tell a friend just how much chocolate there is compared to how much milk. How can you measure / describe this?. Objective Tonight’s Homework.

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Warmup 10/20/14

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  1. Warmup10/20/14 Let's say you make some chocolate milk one day. You try it and it's REALLY good. You want to tell a friend just how much chocolate there is compared to how much milk. How can you measure / describe this? Objective Tonight’s Homework To learn how we measure the concentration of a liquid. pp 205: 46, 47, 48, 49

  2. Notes on Molarity Let’s say we have some lemonade. Then we add a bunch of water to it. Will this change the taste?

  3. Notes on Molarity Let’s say we have some lemonade. Then we add a bunch of water to it. Will this change the taste? Of course! If we add water, we dilute the lemonade. This works with lots of things. Like chemicals…

  4. Notes on Molarity Let’s say we have some lemonade. Then we add a bunch of water to it. Will this change the taste? Of course! If we add water, we dilute the lemonade. This works with lots of things. Like chemicals… Let’s say we wanted to measure the concen-tration of a chemical. How might we do this? With something called “molarity.”

  5. Notes on Molarity Let’s say we have some lemonade. Then we add a bunch of water to it. Will this change the taste? Of course! If we add water, we dilute the lemonade. This works with lots of things. Like chemicals… Let’s say we wanted to measure the concen-tration of a chemical. How might we do this? With something called “molarity.” moles of solute _ volume of solution in L molarity (concentration) =

  6. Notes on Molarity Example: Calculate the molarity when 5.23 g of Fe(NO3)2 in 100.0 cm3 of solution

  7. Notes on Molarity Example: Calculate the molarity when 5.23 g of Fe(NO3)2 in 100.0 cm3 of solution - We need to find how many moles of Ferric (II) Nitrate we have. 5.23 g Fe(NO3)2 1 mol _ 1 179.9 g • = 0.029 mol Fe(NO3)2

  8. Notes on Molarity Example: Calculate the molarity when 5.23 g of Fe(NO3)2 in 100.0 cm3 of solution - We need to find how many moles of Ferric (II) Nitrate we have. 5.23 g Fe(NO3)2 1 mol _ 1 179.9 g - Now we can divide moles by volume. 0.029 mol Fe(NO3)21000 cm3 100.00 cm3 1 L • = 0.029 mol Fe(NO3)2 • = .29 M Fe(NO3)2

  9. Practice with Molarity Take a look at problems 44 and 45 on page 205. Make sure you can do them and know what’s going on. We’ll discuss them as a class in a bit.

  10. Exit Question #30 Calculate the molarity: 8.55 g NH4I in 50.0 cm3 of solution. a) 0.97 M NH4I b) 1.18 M NH4I c) 1.67 M NH4I d) 2.02 M NH4I e) 2.46 M NH4I f) 2.98 M NH4I

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