Hi folks,
This week we took a look at the concept of concentration. Basically, how many particles of something is in a solution. We worked a few molarity problems and some concentration problems. Then we did a fun lab where we used these concepts to discover what molarity of lemonade tastes the best.
For homework please do the enclosed worksheet. Several of these are two step problems so you need to convert to moles first. Answers are included so you can make sure you are on the right track.
Also, please answer the following questions regarding the lab. Answers below.
1. The lemonade container had a mass of 536g. How many moles of lemonade was in the container (just use the molar mass of sugar, C12H22O11, for the molar mass of lemonade)?
2. How many particles of "lemonade" is in the container (in other words, convert moles to particles)?
3. You've discovered that .25 M is the perfect molarity for a perfect tasting lemonade. You are having a party and want to impress all your friends, so you need to make 3 liters of lemonade. What mass of powder would you need? You need to convert moles to mass here. (See, and you thought chemistry wasn't useful.)
4. Whoops. .25M is way too sweet. Let's dilute that to .2M. How much water do you need to add. Use C1V1 = C2V2 here.
5. If you poured the entire jar, all 536g of lemonade, into a 2.2 liters (a gallon) jar, what would the molarity be?
Answers:
1. 1.57 Moles
2. 9.4 x 10^23
3. .25 = m/3 .75 moles so .75x 342 g/mol = 256.5g
4. C1V1 = C2V2
.25 x 3 = .2 x V2
3.75L = V2 So you need to add .75 L of water to dilute it.
5. 1.57/2.2 = .71M (That might be a bit sweet.)
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