Copy of chem lab 5

.docx

School

California State University, Northridge *

*We aren’t endorsed by this school

Course

102L

Subject

Chemistry

Date

Apr 3, 2024

Type

docx

Pages

Uploaded by marcuspen

Edward Avetisyan Richard Engeseth Tuesday 11am-1:50pm 2/20/2023 Chem 102 Lab 5 Objective ● Appyling the concepts of dynamic equilibrium through Le Chatliers principle by observing the effects of disturbing an equilibrium by changing temperature and concentration. Procedures ● Chromate and Dichromate Equilibrium ○ 1) In a clean test tube, place 1-2 mL of 1 M K 2 CrO 4 . Add a few drops of 3 M H 2 SO 4 . Shake the tube and write down the observations made. ○ 2) Add one drop of 6 M NaOH and mix. Continue to add single drops until you observe a color change. ○ 3) Add a few drops of 3 M H 2 SO 4 until you observe a color change. ○ 4) Add one drop of 6 M NaOH and mix. Continue adding single drops until you observe a color change. ● Indicator Equilibrium ○ 1) Place 2-3 mL of deionized water in a test tube and add 2-4 drops of 1% methyl orange. Now add 2 drops of 6 M HCl. Observe and record the color change. Add 4 drops of 6 M NaOH. Observe and record the color change. ○ 2) To one tube, add 1 M sodium acetate a few drops at a time. Mix the solution until you see a change. Compare the color of this tube with the original one and record your observations. ○ 3) Add a few drops of 1 M NH 4 OH, weak base, to each of the solutions. Observe any changes and record your observations. ● Temperature ○ 1) Place 4 mL of .15 M CoCl 2 *6H 2 O dissolved in methanol into a test tube drop- by-drop until the blue solution turns pink. Pour half of the pink solution turns pink. ○ 2) Pour half of the pink solution into a second test tube. ○ 3) To one of the test tubes add 12 M HCl dropwise until you see a color change. ○ 4) Heat the second test tube (no acid) in a water bath filled with hot water. If there is no color change, raise the temperature of the water bath. ○ 5) Using the solution you heated in step 4, place the test tube in an ice bath. ● Concentration and temperature ○ 1) Place around 4 mL of saturated KCl solution into a test tube. Carefully add 2 mL of concentrated 12 M HCl. Mix the solution.

○ 2) Warm the solution using a beaker of hot water on a hot plate. Note the presence of absence of precipitate and the amount of precipitate. Observations/ Results Chromate and dichromate equilibrium CrO 4 2- (aq) + 2 H + (aq) Cr ⇌ 2 O 7 2- (aq) + H 2 O(l) 1. (½ point) What substance, chromate or dichromate, is most abundant if the solution is yellow? Chromate 2. (½ point) What substance, chromate or dichromate, is most abundant if the solution is orange? DiChromate 3. (1 point) Addition of H + (aq) to the above equilibrium produces an Orange (insert color) solution and pushes the equilibrium to the Right (left/right) 4. (1 point) Addition of OH - (aq) to the above equilibrium produces an Yellow (insert color) solution and pushes the equilibrium to the Left (left/right) Indicator Equilibria The equilibria are generalized as: HIn(aq) H ⇌ + (aq) + In - (aq) 1. (½ point) What color is HIn for methyl orange? HIn for methyl orange 2. (½ point) What color is In - for methyl orange? In - 3. (½ point) Which way does the methyl orange equilibrium above shift upon addition of HCl? Upon addition of HCl equilibrium shifts left

4. (½ point) Which way does the methyl orange equilibrium above shift upon addition of NaOH? Upon addition of NaOH equilibrium shifts right 5. (½ point) What color is HIn for phenolphthalein? HIn of phenolphthalein is colorless 6. (½ point) What color is In - for phenolphthalein? In - for phenothalien is pink 7. (½ point) Which way does the phenolphthalein equilibrium above shift upon addition of HCl? Upon addition of HCl equilibrium shifts to the left 8. (½ point) Which way does the phenolphthalein equilibrium above shift upon addition of NaOH? Upon addition of NaOH the phenophthalien equilibrium shifts to the right Weak Acid Equilibria HCH 3 CO 2 (aq) CH ⇌ 3 CO 2 - (aq) + H + (aq) 1. (½ point) What color is the acetic acid plus methyl orange solution and what does this tell you about where the equilibrium is? The color of the solution is orange and the indicator equilibrium will shift towards the right 2. (½ point) What color is the acetic acid plus methyl orange after addition of sodium acetate solution and what does this tell you about where the equilibrium is? The color of the solution is yellow due to the formation of acetate ion from sodium acetate the dissociation of acetic acid reduces and pH increases. The indicator equilibrium will shift towards the left.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Recommended textbooks for you

Chemistry for Engineering Students

Chemistry

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Cengage Learning

Introductory Chemistry: An Active Learning Approa...

Chemistry

ISBN:9781305079250

Author:Mark S. Cracolice, Ed Peters

Publisher:Cengage Learning

Introductory Chemistry: A Foundation

Chemistry

ISBN:9781337399425

Author:Steven S. Zumdahl, Donald J. DeCoste

Publisher:Cengage Learning

Chemistry: The Molecular Science

Chemistry

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:Cengage Learning

Chemistry

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Cengage Learning

Chemistry & Chemical Reactivity

Chemistry

ISBN:9781337399074

Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel

Publisher:Cengage Learning

SEE MORE TEXTBOOKS

Recommended textbooks for you

Chemistry for Engineering Students
Chemistry
ISBN:9781337398909
Author:Lawrence S. Brown, Tom Holme
Publisher:Cengage Learning
Introductory Chemistry: An Active Learning Approa...
Chemistry
ISBN:9781305079250
Author:Mark S. Cracolice, Ed Peters
Publisher:Cengage Learning
Introductory Chemistry: A Foundation
Chemistry
ISBN:9781337399425
Author:Steven S. Zumdahl, Donald J. DeCoste
Publisher:Cengage Learning
Chemistry: The Molecular Science
Chemistry
ISBN:9781285199047
Author:John W. Moore, Conrad L. Stanitski
Publisher:Cengage Learning
Chemistry
Chemistry
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Cengage Learning
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781337399074
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning