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Chapter 18. Acids and Bases Rainbow Connection #2. Ch. 18- Acids and Bases. Acids and bases have a central role in chemistry They affect our daily life Uses: manufacturing processes, environmental issues, functioning of our bodies Acid/ Base Video. Properties of Acids. Have pH  0-6

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Chapter 18

Chapter 18

Acids and Bases

Rainbow Connection

#2


Ch 18 acids and bases
Ch. 18- Acids and Bases

  • Acids and bases have a central role in chemistry

  • They affect our daily life

  • Uses: manufacturing processes, environmental issues, functioning of our bodies

  • Acid/ Base Video


Properties of acids
Properties of Acids

  • Have pH  0-6

  • Tart or sour taste

  • Will conduct electricity

  • Cause indicators to change color (turns blue litmus red)

  • Reacts w/ metals (Mg,Zn) to form H2 gas

  • Neutralize w/ a base forms a salt and H20

  • Ex. Citrus foods, tomatoes, vinegar


Acid formulas memorize
Acid Formulas (memorize)

  • HCl ( Hydrochloric Acid)

  • HNO3 (nitric acid)

  • H2SO4 (sulfuric acid)

  • H2CO3 (carbonic acid)

  • HC2H3O2 (acetic acid)

  • H3PO4 (phosphoric acid)


Properties of bases
Properties of Bases

  • Also known as alkaline

  • pH  8-14

  • Have a bitter taste, slippery feel

  • Causes indicators to change color (turns red litmus blue)

  • Conducts electricity

  • Reacts w/ acid to neutralize  form a salt and H2O

  • Ex. Cleaning products, soap, baking soda


Acid base theories
Acid/ Base Theories

  • Definitions have changed over the years as new information has been found

  • Arrhenius Theory video


Arrhenius theory 1887
Arrhenius Theory (1887)

  • Applies to a H2O solution

  • Svante Arrhenius (Swedish) saw that not only do acids/ bases conduct electricity, they ionize (or release charged particles) when dissolved in water

  • Theory:

    • Acids- substance that ionize & produced (H+) hydrogen ions in H2O

    • Bases- ionize to produce (OH-) hydroxide ions in H2O


Ex. HCl  H+(aq) + Cl-(aq)

ACID

NaOH  Na+(aq) + OH-(aq)

BASE


Br nsted lowry theory 1923 video
Brønsted- Lowry Theory (1923) (video)

  • Working independently of each other, Johannes Brønsted (Danish) and Thomas Lowry (English) defined a theory that can be used w/ all solvents not just H2O (they found that substance lost or gained protons)

  • Acid- in a chemical reaction, this is the substance that loses or donates a proton (H+ ion)

  • Base- substance that accepts or gains a proton (H+ ion = proton)


Accepts proton (base)

Donates (loses) proton – (acid)

H3O+  hydronium ion (formed when H2O gains H+ ion)


  • NH3 + H2O  NH4+ + OH-

Accepts proton (base)

Donates (loses) proton – (acid)

Amphoteric – (H2O) acts as an acid or a base (depending on the situation)


Conjugates
Conjugates

  • The particles that are formed as products can react again (reversible reaction), they behave like acids and bases (we call these conjugates)

  • Conjugate video


  • Conjugate Acid - Particle that forms after the base accepts a proton (H+) from the acid

  • Conjugate Base – particle that remains after a proton (H+) has been released by the acid


Ex.

HNO3 + NaOH  H2O + NaNO3

(H-OH)

Acid

Conjugate Base

Base

Conjugate acid



Ex.

KOH + HBr  KBr + H2O

Base

Conjugate Acid

Acid

Conjugate Base


Neutralization reaction
Neutralization Reaction

  • Occurs when an acid and a base react and there is a complete removal of all of the H+ and OH- ions

  • Water will be formed w/ a salt in this double displacement reaction

  • The solution will be neutral in pH

  • Important in: neutralization of soil, antacids


Salt

  • Crystalline compound composed of the negative (non-metal) ion of the acid and the positive (metallic ) ion of the base

  • Salt examples: CaSO4 (plaster board), NaCl, KCl, (NH4)2SO4 (fertilizer)


Examples of neutralization reactions
Examples of Neutralization Reactions

  • Sodium hydroxide + hydrochloric acid  sodium chloride + water

  • NaOH + HCl  NaCl + H2O (H-OH)


H- OH + K2SO4

2 KOH + H2SO4 2 H-OH + K2SO4




Titration1
Titration

  • Used for a convenient method to determine the concentration or molarity of an acid or base

  • Uses 2 burets (long glass tubes used to measure volume)- Buret + .05 ml


Definition
Definition

  • Analytical method in which a standard solution is used to determine the concentration of another solution

  • Standard solution- one in which the concentration is known


Process
Process

  • Using a given amount of acid in a flask, add phenolphthalein and titrate to the end point with the base (making sure to mark down all the volumes)

  • The whole reaction is a neutralization reaction

  • Use an indicator to see the endpoint in which complete neutralization occurs (wait for phenolphthalein stays light pink for 30 sec)


Past endpoint

Endpoint



Calculations
Calculations

  • Reminder: M= moles

  • liters

  • So: Base (titrated soln) 

    • Moles (base) = volume (base) x Molarity (base)

      Acid (standard soln) 

      Moles (acid) = volume (acid) x Molarity (acid)



Problem
Problem and the moles of the titrated unknown (look at coefficients)

  • A titration of 15.00 ml of HCl, required 38.57 ml of a 0.152 M base NaOH. Calculate the molarity of the HCl (acid).

  • MA = ?


  • M and the moles of the titrated unknown (look at coefficients)A VA = MBVB

  • MA = M BVB

  • VA

  • MA = (.152M) (38.57 ml)

  • (15.00ml)

  • MA = .391 M


Titration calculation
Titration Calculation and the moles of the titrated unknown (look at coefficients)


Id a b ca cb
ID- A, B, CA, CB and the moles of the titrated unknown (look at coefficients)

  • CaCO3 + HCl  CaCl2 + H2CO3

  • KOH + H3PO4 K3PO4 + H2O


  • phosphoric acid + calcium hydroxide and the moles of the titrated unknown (look at coefficients)calcium phosphate + water

  • HBr + Al(OH)3

  • Sulfuric acid + potassium hydroxide 


Indicators
Indicators and the moles of the titrated unknown (look at coefficients)

  • Used to find out if things are acidic or basic

  • Def: weak organic acids or bases whose colors differ from the colors of their conjugate acids or bases

base

acid


Needs of indicators
Needs of Indicators and the moles of the titrated unknown (look at coefficients)

  • Solution being tested needs to be colorless

  • You need to be able to distinguish the color change

  • Need several indicators to cover entire pH range (0-14)

  • Liquid solution


Indicator examples
Indicator Examples and the moles of the titrated unknown (look at coefficients)

  • Litmus  red turns blue = base, blue turns red = acid

  • Phenolphthalein hot pink > pH 10

  • Bromothymol blue  blue= base (8), Green= neutral, yellow = acid (6)

  • Universal Indicator  Rainbow (all pH’s 4-10)

  • (bromothymol blues)


How chemists use indicators
How Chemists use Indicators and the moles of the titrated unknown (look at coefficients)


Ionization of h 2 o
Ionization of H and the moles of the titrated unknown (look at coefficients)2O

  • Pure water can self ionize, it also acts as an acid or a base (amphoteric)

  • So: H2O(aq) H+(aq) + OH-(aq)

  • Experiments have shown that the concentration of [H+] = 1 X 10 –7M and [OH-] = 1 x 10 –7 M in pure water

  • [ ] means concentration


Ion product constant for water
Ion Product Constant for water and the moles of the titrated unknown (look at coefficients)

  • Equilibrium expression from the multiplication of the concentrations of the products

  • [H+] [OH-] =?

  • (1 x 10 –7)(1 x 10 –7) = 1.0 x 10 -14

  • [H+] [OH-] = 1.0 x 10 -14


  • If [H and the moles of the titrated unknown (look at coefficients)+] = 1.5 x 10 -6 M, what is the [OH-] = ?

  • [H+] [OH-] = 1.0 x 10 -14

  • (1.5 x 10 -6) [OH-] = 1.0 x 10 -14

  • [OH-] = 1.0 x 10 -14

  • 1.5 x 10 -6

  • [OH- ] = 6.7 x 10-9 M


Ph concept video
pH Concept ( and the moles of the titrated unknown (look at coefficients)video)

  • Acidity scale developed by Soren Sorenson base on the “power of the hydrogen”

  • pH – measure of the hydrogen ion concentration of the solution

    • Equal to the negative logarithm of the hydrogen ion concentration

      2. pH = - log [H+]


Ex. [H and the moles of the titrated unknown (look at coefficients)+] = 1.5 x 10-8

pH= ?

Graphing Calc.

(-) log 1.5 (2nd) EE -8

Regular calc.

1.5 EE -8 log +/- pH= 7.8


To go from ph to h concentration
To go from pH to [H and the moles of the titrated unknown (look at coefficients)+]concentration

3. [H+] = antilog (-pH)

Antilog = 10x key


  • pH= 3.5 and the moles of the titrated unknown (look at coefficients)

  • [H+] = ?

    [H+] = antilog (-pH)

    [H+] = antilog (-3.5)

    Graphing = 2nd log -3.5

    Regular 3.5 +/- 2nd log

    (to put in sci.not. Use 2nd #5)

    [H+] = 3.2 x 10 -4 M


Poh hydroxide power
pOH (hydroxide power) and the moles of the titrated unknown (look at coefficients)

  • pH + pOH =14

    • pH= 8

    • pOH = ?

      8 + ? = 14 pOH= 6

  • pOH = - log [OH-]

  • [OH-] = antilog (-pOH)


[H+] = 3.5 x 10 and the moles of the titrated unknown (look at coefficients)-7 M, [OH-] = ?

pH = 8.95 , [H+] = ?

[OH-] = 5.65 x 10 -2 M, pOH = ?

pOH= 11.9, [H+] = ??

Formula 1

Formula 3

Formula 5

Formula 4, then 3 or

Formula 6, then 1


Rosengarten acid and base video
Rosengarten acid and base video and the moles of the titrated unknown (look at coefficients)


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