1 / 15

pH and Water

pH and Water. Understanding the Properties of the Essential Water Molecule. pH. pH = -(log [H + ]) [H + ] = concentration of Hydrogen ions For [H + ] = 10 -2 , pH = 2 Each change in pH represents 10x change in [H + ] and [OH - ] pH of 7 is neutral; [H + ] = [OH - ]

silas
Download Presentation

pH and Water

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. pH and Water Understanding the Properties of the Essential Water Molecule

  2. pH • pH = -(log [H+]) • [H+] = concentration of Hydrogen ions • For [H+] = 10-2, pH = 2 • Each change in pH represents 10x change in [H+] and [OH-] • pH of 7 is neutral; [H+] = [OH-] • pH < 7 is acidic; [H+] > [OH-] • pH > 7 is basic; [H+] < [OH-]

  3. Complete this sentence: Coffee has (A)______ fold (B)______ (C) ______ than water. • (A) • 1 • 10 • 100 • 1000 • 10000 • (B) • Less • More • The same amount • (C) • [H+] • [OH-] Applying Your Knowledge Given: Coffee has a pH value of 5. Pure water has a pH value of 7.

  4. Experiments for Today • pH • Buffers • Specific Heat Experiment • Heat of Vaporization • Surface Tension/Capillary Action

  5. pH Experiment • Handle the small pieces of pH paper with forceps. • Using wooden stick, dot paper with test solution and read when wet. • Test at least three solutions and share information with classmates to get a full set of data.

  6. Carbonation • CO2 occurs in aqueous solutions through • Injection: carbonation in soft drinks and sparkling water • Yeast fermentation: beer and sparkling wines • In water, CO2 forms carbonic acid CO2 + H2 O  H2 CO3  H+ + HCO3 -

  7. Buffers • Buffers resist changes in pH • Buffers have substances that can bind to excess H+ and/or OH- • Blood and milk contain proteins that can absorb H+ and OH- ions.

  8. Add NaOH Add HCl H2O H2O H2O Add HCl Add NaOH Milk Milk Milk Buffer Experiment Check pH Add HCl, stir Add NaOH, Stir Check pH Check pH

  9. Specific Heat • Specific heat = amount of heat needed to raise the temperature of 1 gram of a solution by 1o C • Experiment compares heating and cooling rates of water and ethyl alcohol

  10. Place both beakers in ice water bath and allow temperatures to equalize (~10 min). • Switch beakers to warm water bath. Monitor and record the temperatures of both solutions every 30 seconds for 5 minutes. • Switch beakers to ice water bath. Monitor and record the temperatures of both solutions every 30 seconds for 5 minutes. Ice water Warm water Ice water

  11. Heat of Vaporization • Heat of vaporization = amount of heat needed to change a liquid into a gas • Experiment compares the sensations that occur with evaporation of water and ethyl alcohol

  12. Heat of Vaporization • Blind experiment • Subject is unaware of treatment • Double-blind experiment • Subject and tester are both unaware of treatment • Requires help of third party

  13. Capillary Action • Capillary Action – movement of water through a tube by adhesion and cohesion • Experiment involves comparisons of water and alcohol moving up glass and plastic tubes of varying diameters • Note the liquid level and degree of curvature of liquid surface inside tube

  14. CLEAN UP! • Rinse and clean all glassware • Place used pH strips in the discard container • Pour ethyl alcohol into to the “USED” container • Exercise care in using your thermometer to avoid breakage

  15. Worksheet • Complete pages 21-25 from lab manual • Be sure your instructor checks your completed worksheet before you leave the lab

More Related