New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Chem 14BL- Week 3 Notes

by: Daniel Ochs

Chem 14BL- Week 3 Notes CHEM 14BL

Daniel Ochs

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Week 3 Notes
General and Organic Chemistry Laboratory I
Class Notes
25 ?




Popular in General and Organic Chemistry Laboratory I

Popular in Chemistry and Biochemistry

This 12 page Class Notes was uploaded by Daniel Ochs on Tuesday April 19, 2016. The Class Notes belongs to CHEM 14BL at University of California - Los Angeles taught by Casey in Spring 2016. Since its upload, it has received 12 views. For similar materials see General and Organic Chemistry Laboratory I in Chemistry and Biochemistry at University of California - Los Angeles.


Reviews for Chem 14BL- Week 3 Notes


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 04/19/16
Week 3 Notes Recrystalization- Single Solvent Goal: Purify an impure or crude experimentally synthesized product Basic Principle: Solubility of a compound usually increases with increasing temperature of the solvent (solubility depends on concentration, polarity, and temperature) Major Difficulty: Most impurities and reaction by-products have similar solubility properties as the desired product. 1.  Dissolve the impure product in a minimum amount of a soluble hot solvent.
 2.  Filter the hot solution to remove any insoluble impuri
ies. 3.  Let the solution cool slowly to allow the pure crystal form without trapping impu
ities. 4.  Filter the purified product Solubility in Recrystalization Example 2: Suppose we take 25 g of sugar and dissolve it in 10 mL of boiling water. We then allow the solution to slowly cool down to room temperature. Will we observe any sugar crystals in the cooled solution? Example 3: Suppose we take 25 g of sugar and dissolve it in 12.5 mL of boiling water. We then allow the solution to slowly cool down to room temperature. Will we observe any sugar crystals in the cooled solution? Solubility of Sugar in Water Temperature 1.80 g/mL 25 C Using excess solvent in a recrystallization will reduce 2.50 g/mL 100 C the amount of recovered purified product (lower yield!) Example 2:
 At 100 C: 2.50 gml×10ml = 25g [Can dissolve all sugar] o 1.80 ×10ml=18g [Cannot dissolve all sugar] At25 C: ml 25g initially dissolved - 18 g remaining in solution = 7 g or sugar cyrstals formed Example 3: At 100 C: 2.50 gml×12.5ml = 31.25g [Can dissolve all sugar] At 25 C: 1.80 g ×12.5ml = 22.5g [Cannot dissolve all sugar] ml 25g initially dissolved - 22.5 g remaining in solution = ONLY 2.5 g of sugar crystals formed Using Recrystalization to Remove Impurities Consider the example system where we have 10 g of desired product (A) and 2 g of impurity (B) Temp = 20°C Temp =100°C solubility (0.1 g/mL 1 g/mL solubility (B0.1 g/mL 1 g/mL Dissolve all crude product (10 gAand 2 g B) in 12 mL of solvent at 100oC. 
 Cooling to 20oC, 1.2 g ofAand and 1.2 g of B remain in solution while 8.8 g ofAand 0.8 g of B crystalize out. 
 Before recrystallization 10g / 12g ×100% = 83.3% 12g After recrystallization 8.8g / 9.6g ×100% = 91.7% Choosing a Good Crystallization Solvent A good crystallization solvent should: Be soluble for (dissolve) a large quantity of the product at high temperature 
 Be insoluble for (not dissolve) the product at low temperature 
 Be soluble for (dissolve) the impurities at all temperatures [Optional, becuase very difficult to achieve] 
 Not react with the product 
 Considering Crystalization of Glycine Example 4: Is water or ethanol a better solvent for glycine? Solubility of Glycine in Water Temperature Solubility of Glycine in Ethanol Temperature 14.0 g/100 mL 0 C 0.01 g/ 100 mL 0 C 25 g/ 100 mL 25 C 39 g/ 100 mL 50 C 45 g/ 100 mL 25 C 54 g/ 100 mL 75 C o o 65 g/ 100 mL 65 C 67 g/ 100 mL 100 C Considering Crystalization of Glycine 
 Example 4: Is water or ethanol a better solvent for glycine? Use percent recovery to decide (amount dissolved at high T - amount at low T / amount at high T) x 100% = Percent Recovery Using water as the solvent: (67 g -14 g) / 67 g % recovery = ×100% = 79% Using ethanol as the solvent: [Preferred Solution] % recovery =(65 g - 0.01g) / 6×100% = 99.98% Synthesis of Aspirn Lab 
 salicylic acid (limiting reagent) + acetic anhydride ——> aspirin + acetic acid Example 5: When performing the aspirin lab, you weigh out exactly 3 g of salicylic acid (SA). Given that you made 3.21 g of aspirin (A) after recrystallization, what is the % yield? 3gSA 1mol SA / 138.1g SA) 1mol A / 1 mol SA)180.2g A / 1 mol A=3.91g % yield = actual amount / theoretical amount ×100% = 3.21 g / 3.91 g×100% = 82.1% Recrystalization of Aspirin What solvent do we use to recrystalize aspirin? Water: not very soluble Ethanol: way too soluble Solubility ofAspirin in Water Temperature Solubility of Aspirin in Temperature 0.025 g / 100 mL of wat0 C Ethanol 0.30 g / 100 mL of wate25 C 20.0 g / 100 mL 25 C of ethanol 1.0 g / 100 mL of water37 C 35.0 g / 100 mL o of ethanol 70 C Decomposes at high T o 100 C Mixed Solvent System for Recrystalization • Made with two mutually miscible (mixable) liquids 
 • One of the two solvents will dissolve the product more readily than the other solvent 
 • Usually works better than single solvent system 
 We will use a mixed solvent recrystallization for purifying aspirin – use a mixture of water and ethanol! 
 Procedurte for Recrystalization with Mixed Solvent System •  Dissolve the impure product in the high-solubility solvent (ethanol) at high temperature. 
 •  Add the low-solubility solvent (water) drop-wise until solution turns cloudy. 
 •  Heat solution to re-dissolve all crystals. Add a few drops of high- solubility solvent (ethanol) if required to force all the crystals back into solution 
 •  Allow solution to cool slowly to allow the pure products to form without trapping impurities. 
 Graphs •Online in powerpoint provided and in notes


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Steve Martinelli UC Los Angeles

"There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

Anthony Lee UC Santa Barbara

"I bought an awesome study guide, which helped me get an A in my Math 34B class this quarter!"

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.