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Aim AB 1a What are the properties of Acids and Bases?

Learn about electrolytes and their ability to conduct electricity. Discover the properties of acids and bases, including taste, corrosiveness, and their reactions with metals. Explore the pH scale and common acids and bases used in real-world applications.

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Aim AB 1a What are the properties of Acids and Bases?

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  1. Aim AB 1aWhat are the properties of Acids and Bases?

  2. Question: What is an electrolyte? • Electrolytes – think Gatorade! • As substances dissolve, ionicsubstances release free ions • Ions carry a charge • Electrolytes can therefore carry electricity • How do we test for electrolyte solutions?

  3. Properties of Acids • Examples to the right; what do they have in common? • They are all electrolytes – conduct electricity when aqueous • They taste sour – think lemons • They are corrosive - break down materials • React with active metals to release hydrogen gas Ex: HCl(aq) + Mg(s) MgCl(aq) + H2(g) • Neutralize bases to form a salt and water in a double replacement reaction Ex: HCl(aq) + NaOH(s) NaCl(aq) + HOH(l) ACID base salt water

  4. Properties of Acids • Cause color changes in indicators (A chemical that reacts with an acid or base and shows a color change) • blue litmus paper • changes to red • (aciD = reD) • phenolphthalein solution • changes to clear • pH scale – indicates level of acidity or basicity of a solution • pH of 1 – 6 indicates an acid • pH of 7 is neutral • pH of 8 – 14 indicates a base

  5. Commonly used Acids Regents Chemistry Table K Common Acids • Monoprotic acid • only one H+ released • HCl, HNO3 • Diprotic acid • Two H+ ions released • H2CO3, H2SO4 • Triprotic acid • Three H+ ions released • H3PO4

  6. Properties of Bases • Examples to the right; what do they have in common? • They are all electrolytes – conduct electricity when aqueous • They taste bitter – what does that tell you about coffee, especially Starbucks? • They are caustic – break down skin tissue • Feel slippery to the touch – many soaps have this characteristic • Neutralize bases to form a salt and water in a double replacement reaction Ex: HCl(aq) + NaOH(s) NaCl(aq) + HOH(l) acid BASE salt water

  7. Properties of Bases • Cause color changes in indicators • red litmus paper • changes to blue color • (Blue = Base) • Phenolphthalein solution • changes to pink color • pH scale – indicates level of acidity or basicity of a solution • pH of 1 – 6 indicates an acid • pH of 7 is neutral • pH of 8 – 14 indicates a base

  8. Commonly used Bases Regents Chemistry • Monohydroxy base -only one OH- released • NaOH, KOH • Dihydroxy base -two OH- ions released • Ca(OH)2 • Ammonia – special case (more later) Table K Common Bases

  9. Real World Acid/Base Applications • Acid Rain • Forms from the reactions of sulfur and nitrogen oxides reacting with moisture in the air • Increases the acidity of rainwater • Falls into lakes and ponds • Eats at metals in the lakebeds, ionizing them and polluting the lakes and ponds • Remediation – add lime (base material) to neutralize the acid in the lake – expensive!

  10. Uses of Acids • CH3COOH - Acetic acid • Vinegar in very dilute solution form (3% solution) • HCl – hydrochloric acid • pH control for swimming pools • Cleaning material for tiles "muriatic acid“ • H2SO4 - sulfuric acid • battery acid in your car • HNO3 – nitric acid • Reaction with ammonia to make fertilizers • Reaction with glycerol and toluene to make TNT • H3PO4 – phosphoric acid • can be used to remove rust

  11. Uses of Bases • NaOH – sodium hydroxide • one of the most used bases in industrial processes, also called "lye" and is in some soaps • can be used as a drain cleaner • NH3 – ammonia • most common use as a home cleaner • Used in the production of fertilizers • NaHCO3 - sodium bicarbonate • is present in most baking powder • CaO – calcium oxide – when mixed with water, creates Ca(OH)2 – calcium hydroxide • used in plaster, called quicklime

  12. Aim AB 2b How do we explain the difference between Acids and Bases on a molecular level?

  13. Acid/Base Theories • There are two theories that describe the difference between acids and bases on the atomic level • Arrhenius Theory compares acids and bases in terms of two ions • Arrhenius Acids – release hydrogen ions (H+) when dissolved in solution • Arrhenius Bases – release hydroxide ions (OH-) when dissolved in solution • Bronsted Lowry Theory (also known as the “other” theory in Regents Chemistry) describes acids and bases in terms of being able to donate or accept a proton

  14. Arrhenius Theory of Acids and Bases An Arrhenius Acid is: A substance that ionizes in water to produce hydrogen ions (H+) Since H+ ions can’t exist alone in solution, they combine with water to form hydronium ions (H3O+) HCl(g) H+(aq) + Cl–(aq) or H2O(l) + HCl(g) H3O+(aq) + Cl–(aq)

  15. Arrhenius Theory of Acids and Bases An Arrhenius Base is: A substance that ionizes in water to produce hydroxide ions (OH-) NaOH(s) Na+(aq) + OH–(aq) Note!!! Carbon compounds with hydroxide ions (OH-) are NOT bases – they are alcohols and are neither acid nor base! Examples: CH4OH (methanol) and C2H5OH (ethanol)

  16. Other Theories: • Bronsted-Lowry Theory of Acids • any substance that can donate or give up a proton (proton = H+ ion) • Example: NH4+ (ammonium) can donate a proton H20(l) + NH4+ NH3(aq) + H2O+(aq) • Bronsted Lowry Theory of Bases • any substance that can accept a proton • Usually have a free, unshared pair of electrons that the proton (H+) can attach to • NH3 (ammonia) has an unshared pair of electrons H2O(l) + NH3 NH4+ (aq) + OH-(aq)

  17. Other Theories • Bronsted-Lowry Theory describes how some molecules can act as either an acid or a base • These are Amphiprotic or Amphoteric substances • They have hydrogen ions to give up like an acid • They have unshared electrons to absorb hydrogen ions like a base • Depending on what molecules they hook up with, they can act as either an acid or base

  18. Other Theories • Examples of Amphiprotic or Amphoteric substances • Water can donateoraccept a H+ ion H2O(l) + H2O(l) H3O+(aq) + OH-(aq) Base Acid Acid Base • Ammonia can donate a H+ ionlike an acid NH3(g) + H2O(g) NH2-(aq) + H3O+(aq) Acid Base Base Acid • or accept a H+ ion like a base NH3(g) + H2O(g) NH4+(aq) + OH-(aq) Base Acid Acid Base

  19. Aim AB 3c- Why does lemon juice sting when I get it in my eye?

  20. How does acid cause ulcers and heartburn? • A property of acids is their corrosiveness • This includes your stomach lining when you are stressed or eat overly spicey food • Why do acids have this characteristic? • Its all in their pH

  21. Symbol for concentration [ ] [X] = Concentration of X pH – how acidic or basic a substance is • REMEMBER = Water is polar • Slightly (+) hydrogens of one water molecule • Are attracted to (-) oxygens of another • Because of this, water ionizes (forms (+) and (-) ions) to a very small extent: H2O + H2O  H3O+ + OH– Acid part Base part of water of water

  22. Symbol for concentration [ ] [X] = Concentration of X pH – how acidic or basic a substance is • For every water molecule that becomes an acid ion, one becomes a base ion • This evens out • for every H3O+ ion there is an OH– ion • When they combine, they make 2 water molecules • The concentration of the ions in pure water is measured in moles/liter (molarity) [H3O+] = 10–7 M or 0.0000001 M [OH–] = 10–7 M or 0.0000001 M

  23. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • The acid and base concentrations, when multiplied together, equals a constant value: [H3O+] = 10–7 M [OH–] = 10–7 M [H3O+] x [OH–] = 10–14 M [Acid] x [Base] = constant • In any solution, including acids or bases • The concentration constant of [H3O+] x [OH–] is equal to 10-14 M

  24. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • In acids, there are more H3O+ ions (acid ions) than OH– ions (base ions) • Example: HCl is added to water. The H+ concentration rises to 10-4 M. What would the OH- concentration be? [H3O+ ] x [OH-] = 10-14 M 10-4 x [OH-] = 10-14 M [OH-] = 10-10 M • Note – the bigger the negative exponent, the smaller the amount you are dealing with • [H3O+ ] = 10-4 M = 0.0001 M • [OH-] = 10-10 M = 0.0000000001 M

  25. Symbol for concentration [ ] [X] = Concentration of X pH – how acidic or basic a substance is • In bases, there are more OH– ions (base ions) than H3O+ ions (acid ions) • Example: NaOH is added to water. The OH- concentration rises to 10-3 M. What would the H3O+ concentration be? [H3O+ ] x [OH-] = 10-14 M [H3O+ ] x 10-3 = 10-14 M [H3O+ ] = 10-11 M

  26. So where does pH come from??? • We said in the previous slides the following: • For water, • The [H3O+ ] was 10-7 and the [OH- ] was 10-7 • Its pH is 7, or NEUTRAL • For an acid, • The [H3O+ ] was 10-4 and the [OH- ] was 10-10 • Its pH is 4, or ACIDIC • For a base, • The [H3O+ ] was 10-11 and the [OH- ] was 10-3 • Its pH is 11, or Basic • So, to calculate pH, we look at the exponent of the acid part to get the pH

  27. So, to calculate pH, what do we look at? • Example 1: a solution has a hydronium [H3O+ ] concentration 10-4 M. • What is the hydroxide [OH- ] concentration? • [H3O+ ] x [OH- ] = 10-14 (a constant) • 10-4 M x [OH- ] = 10-14 • [OH- ] = 10-10 • What is the pH of the solution? • Look at the exponent of the [H3O+ ] • [H3O+ ] =10-4 = pH of 4 , acidic

  28. So, to calculate pH, what do we look at? • Example 2: a floor cleaning solution has a hydroxide [OH- ] concentration 10-6 M. • What is the hydronium [H3O+] concentration? • Remember: • [H3O+ ] x [OH- ] = 10-14 (a constant) • [H3O+ ] x 10-6 M x = 10-14 • [H3O+ ] = 10-8 • What is the pH of the solution? • Look at the exponent of the [H3O+ ] • [H3O+ ] =10-8 = pH of 8 , basic

  29. Aim AB 4d Oh no! How do I clean up the Liquid Plumber on my kitchen floor safely?

  30. A student spills a container of acid on the floor. What does the student need to add to the acid to get rid of it? • Wipe it up? • Water it down? • What else could be done? • More than anything else - the acid needs to be neutralized

  31. Neutralization is a special DOUBLE REPLACEMENT reaction • It reacts an acid with a base to form a salt and water • Acid + Base  Water + Salt • General formula • HA + BOH  HOH + BA • Examples • HCl + NaOH  H2O + NaCl • H2SO4 + 2 NaOH 2 H2O + Na2SO4

  32. Neutralization / double replacement - determine the products of each of the following neutralization reactions: 1. KOH + HBr  H2O + KBr 2. H2SO4 + Ca(OH)2  2H2O + CaSO4 • Spectator ions • ions that stay dissolved in the water of a solution, do not react • the ions that make up the soluble salts tend to be spectator ions

  33. Acid Base Indicators tell us how acid or basic a substance is • See Table M for examples of various indicators • The pH range on the chart represents the point that a color change will occur • Values to the left represent more acidic pHs • Values to the right represent more basic pHs

  34. Acid Base Indicator Examples 1. A solution leaves thymol blue a blue color and litmus paper changes to blue; is the solution basic or acidic? • Thymol is blue above the 8.0 – 9.6range • Litmus changes blue above the 5.5 – 8.2 range • Both show the solution above 8 • Solution is most likely basic 2. A solution changes methyl orange and litmus redand has no effect on phenolphthalein. Is it basic or acidic? • Methyl orange changes red below 3.2 – 4.4 • Litmus changes red below 5.5 - 8.2 • Both show the solution below 7 • Solution is most likely acidic

  35. Aim AB 5e– How strong is my vinegar?

  36. Acid Base Titration • A method for determining the concentration or molarity of an unknown acid or base, based on • the molarity of a known acid or base • The volume of acid used • The volume of base used • Uses the process of neutralizationand the concept of endpoint • Endpoint: the point when the last of the acid and base are completely neutralized • Determined using an indicator to show the final neutralization point

  37. To determine the molarity of an unknown acid solution 1 - you choose a good indicator 2 - you choose a known base molarity 3 - you add the base to the acid till it changes color 4 – you calculate

  38. Calculating the molarity of an acid using the titration method and formula • By using the titration technique and the endpoint of the neutralization reaction • We can find out three things 1 - the molarity of the known base ( Mb ) 2 - The volume of the base used ( Vb) 3 - The volume of the acid sample (Va) • We can now use the last of our calculations in CRT T to calculate the Ma x Va = Mb x Vb

  39. Example 1 – a 2.00 M acid solution is used to titrate an unknown base solution. If 40.00 mL of acid are used and 20.0 mL of base are used, what is the molarity of the base? Remember: M is molarity or concentration V is measured in mL or liters Ma x Va = Mb x Vb 2.00 M x 40.0 mL = Mb x 20.0 mL 4.00 M = Mb

  40. Example 2: Tropicana is having an issue with the citric acid levels in its new Tropicana Grapefruit Infused Fresh juice. A quality control chemist determines that 22 mL of an 1.0 M NaOH solution is used to neutralize 4400 mL of acidic TGIF juice. What is the molarity of the juice? Ma x Va = Mb x Vb Ma x 4400.0 mL = 1.00 M x 22.0 mL 0.005 M = Ma What is the pH of the Tropicana? .0050 M = 5.0 x 10-3 = pH of 3

  41. Example 3: A student performs a titration with a known base. She collects the data shown below. If the base has a molarity of 0.120 M, what is the molarity of the acid? How much acid How much base was used? was used? 42.4 mL – 22.4 mL 18.4 mL – 13.4 mL = 20.0 mL = 5.0 mL Ma x 20.0 mL = 0.120 M x 5.0 mL Ma = 0.030 M

  42. Acid / Base Strengths • HCl and H2SO4 release different numbers of H+ ions! • In the neutralization of NaOH, H2SO4 + 2NaOH  2H2O + Na2SO4 • NaOH and Ba(OH)2 also release different numbers of OH- ions! • In the neutralization of Ba(OH)2Note: 2HCl + Ba(OH)2 2H2O + BaCl2

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