Unit11: Acids,Bases,Salts%josephinesclassroom.weebly.com/uploads/3/8/5/3/38536063/unit_eleven_pdf.pdfUnit11: Acids,Bases,Salts% Essential)Question:)What chemical)propertiesdetermine)

Unit 11: Acids-‐Bases-‐Salts Essential Question: What

chemical properties determine the acidity or basicity of a

compound?

Acid v. Base?! 1. SOUR Taste: ex) Lemons, vinegar, tomato paste, carbonated beverages

2. Conduct ELECTRICAL CURRENT: Electrolytes are substances that conduct electrical currents �  this “ability” is dependent on a solution’s ION concentration

�  HIGH concentration = HIGH conductivity = STRONG ACID (and vice-‐versa for weak acids)…more on THIS later! J

Acid v. Base?! 3.  React with BASES to form H2O & SALT: aka

� Neutralization Reaction, which produces SALTS, composed of one (+) metallic or polyatomic ion & one (-‐) non-‐hydroxide (OH-‐) ion

4.  Produces HYDROGEN GAS: see table “J” again! �  metals that are ABOVE H2 will produce hydrogen gas & a salt

5.  Change COLOR of INDICATORS! more on THIS later! J

Acid v. Base?! 1.  BITTER TASTE: like ant-‐acids/milk of magnesia/pepto-‐bismol (chalky)

2.  Slippery/Soapy Feeling…ew! 3.  Conduct ELECTRICAL CURRENT: Just like

acids… HIGH concentration = HIGH conductivity = STRONG BASE (and vice-‐versa for weak bases)…

4.  React with ACIDS to form H2O & SALT! (interdependent…?)

5.  Change COLOR of INDICATORS! more on THIS later! J

Arrhenius Theory � Svante Arrhenius… Swedish chemist � Arrhenius ACID: Hydrogen = (+) ion when in a water solution � ex) HCl à H+ + Cl-‐ � Hydrochloric Acid ionizes in water to form hydrogen and chloride ions

� NOT ALL hydrogen-‐containing substances are acids � ex) Methane, CH4 …these hydrogens remain covalently bonded to “C”, neither being electrolytes NOR an acid

The Hydrogen & Hydronium ION…

� Hydrogen Atom = 1 e-‐ orbiting the nucleus which contains single proton

� Hydrogen Ion: Positive PROTON (+) �  formed when electron lost, leaving behind the proton

�  But here’s the deal…. �  hydrogen won’t STAY a single, positive proton because it’s too darn attracted to any unshared pair of electrons in the water solution!

�  RESULT: Proton covalently bonds with the water forming H3O+

�  Acids dissolve in water and react to produce hydronium and negative ions


HCl + H2O à H3O+ + Cl-‐

�  RESULT: SINGLE Hydrogen Ion produced from each molecule of HCl (according to above equation)

�  ANY acid that produces 1 hydrogen ion = MONOPROTIC H2SO4 à H+ + HSO4-‐

HSO4-‐ à H+ + SO42-‐ = DIPROTIC, or produces TWO hydrogen ions


The Hydroxide ION… (OH-‐) � Arrhenius BASE: Hydroxide = (-‐) ion when in a water solution � Hydroxide ion makes water solution an electrolyte � responsible for: slippery feel/bitter taste

� NH3 = ?? NH3 + H2O à NH4+ + OH-‐

� even though don’t have OH-‐ still a base that forms it when reacted with water!

� **ALCOHOLS (-‐OH groups) are NOT bases! (don’t ionize in H2O)

= ammonia

Naming Acids & Bases � Binary Acids are composed of Hydrogen & 1 other element

How to Name BINARY Acids: (see table “K”)

� start with “Hydro-‐” � followed by name of OTHER element, but with NEW ending… “-‐ic” + word “ACID” � ex) Hydrogen Chloride gas, HCl (g) becomes … � Hydrochloric Acid

Naming Acids & Bases � Ternary Acids are composed of Hydrogen & polyatomic ion that contains Oxygen

How to Name TERNARY Acids: (see table “K”)

� change to new endings �  “-‐ate” becomes “-‐ic” �  “-‐ite” becomes “-‐ous” *however, sometimes names are modiXied slightly!

� Bases = positive ion + add “hydroxide” � ex) Ca(OH)2 =

Ex) HNO3 …. = NITRIC Acid

= Calcium Hydroxide

Naming Acids & Bases -‐ PracGce **Don’t use your reference table..see if you can name these common acids and bases!

HCl H2SO4 H2SO3 HNO3 HNO2 KOH NaOH

Hydrochloric Acid Sulfuric Acid Sulfurous Acid Nitric Acid Nitrous Acid Potassium Hydroxide Sodium Hydroxide

Acid-‐Base ReacGons � REMEMBER! any METAL above H2 on table J will react with an acid to make H2 and a salt!

Ex) Zinc and Hydrochloric Acid � will it react?? � Zn (s) + 2 HCl (aq) à

� ….will Copper react with hydrogen ions in acids � NO, because it’s BELOW Hydrogen Gas on table J!!

H2 (g) + ZnCl2 (aq)

YES! Zinc is ABOVE H2!

NeutralizaGon ReacGons � Arrhenius Acid reacts with Arrhenius Base to make water and salt

Ex) Hydrochloric Acid & Sodium Hydroxide � HCl(aq) + NaOH(aq) à

ACID + BASE à WATER + SALT

à Write IONIC EQUATION:

H+(aq)+Cl-‐(aq)+Na+(aq)+OH-‐(aq)àH2O(l)+Na+(aq)+Cl-‐(aq)

�  NOTE: Na & Cl ions are on BOTH SIDES; left unchanged and are SPECTATOR IONS = can be OMITTED

H2O (l) + NaCl (aq)

NeutralizaGon ReacGons H+(aq)+Cl-‐(aq)+Na+(aq)+OH-‐(aq)

à

H2O(l)+Na+(aq)+Cl-‐(aq)

� SO, omitting spectator ions yields the NET EQUATION…

H+ (aq) + OH-‐(aq) à H2O(l)

� All neutralization reactions have the same net equation

NeutralizaGon ReacGons Write the equation for the neutralization reaction between dilute Nitric Acid & Potassium Hydroxide…

Nitric Acid = Potassium Hydroxide =

sample: Acid + Base à Water + Salt

HNO3 + KOH à H2O + salt

*salt created from positive ion of the base and negative ion of the acid

therefore: HNO3 + KOH à H2O + KNO3 *always check the equation is BALANCED!*

HNO3 KOH

NeutralizaGon ReacGons Write the equation for the neutralization reaction between Calcium Hydroxide & Sulfuric Acid… Sulfuric Acid =

Calcium Hydroxide =


H2SO4 + Ca(OH)2 à H2O + salt

therefore: H2SO4 + Ca(OH)2 à 2H2O + CaSO4

H2SO4

Ca(OH)2

NeutralizaGon ReacGons Write the equation for the neutralization reaction between Magnesium Hydroxide & Hydrochloric Acid.. Hydrochloric Acid =

Magnesium Hydroxide =


HCl+ Mg(OH)2 à H2O + salt

therefore: 2HCl + Mg(OH)2 à 2H2O + MgCl2

HCl

Mg(OH)2

NeutralizaGon ReacGons PracGce Which compound reacts with an acid to produce water and a salt?...

� CH3Cl

� CH3COOH

� KCl � KOH

**KOH**

NeutralizaGon ReacGons PracGce Which compound represents a salt...

� KOH � KCl

� CH3OH

� CH3COOH

**KCl**

NeutralizaGon ReacGons PracGce Write the balanced equation for the following neutralization rxns & write name of SALT formed…

Phosphoric Acid & Lithium Hydroxide

� H3PO4 + 3LiOH à 3H2O + Li3PO4 Nitric Acid & Sodium Hydroxide

� HNO3 + NaOH à H2O + NaNO3 Sulfuric Acid & Magnesium Hydroxide

� H2SO4 + Mg(OH)2 à 2H2O + MgSO4

Lithium Phosphate

Sodium Nitrate

Magnesium Sulfate

Acidity v. Alkalinity So, if H2O has BOTH H+ and OH-‐, then is it an acid or base?

It’s both! Water is Amphoteric, meaning it can take on the role of an acid OR base depending on it’s environment!

…according to Le Châtelier’s Principle:

HOH H+ + OH-‐ SO… [H+] = [OH-‐]

à If ONE of these factors increases, the other decreases à Therefore: When [H+] increases, it becomes ACIDIC & when [OH-‐] increases, it becomes BASIC à Measure of Basicity = ALKALINITY

pH Scale What exactly IS pH and how is it related to acids and bases?

�  pH is a scale that expresses [H+] as a # between 0 & 14. � WATER is NEUTRAL…pH = 7 �  Each single digit change represents a change of 10, so moving from pH 5 to 7 is a change of 100

�  ACIDIC = 0-‐6 BASIC = 8-‐14

pH Scale

WATER

BASIC “B”

pH Scale – conclusions?

Why bother using this scale? What can we conclude from it?

�  If something has a HIGHER pH, then how can we describe it in terms of it’s concentration… �  LOWER [H+], less acidic

�  This means there are fewer ___________ in solution! �  PROTONS!

Indicators – Table M �  Indicators change color when they gain or lose protons… aka Hydrogen Ions

� Most commonly used/heard of academically = LITMUS �  Common indicators: �  Phenolphthalein � Methyl Orange

�  In order for a change in color to occur it has to be BELOW or ABOVE the indicated #s on table M �  Ex) LITMUS paper will turn RED below 4.5 and turn BLUE above 8.3

�  Bromthymol blue �  Litmus

Acid-‐Base TitraGons How can we determine the concentration of an unknown acid or base via a neutralization reaction?

NEUTRAL =

Therefore: # moles Acid = # moles Base

…. # moles H+ = moles OH-‐

M1V1 = M2V2 or MAVA = MBVB

*see table T!! (titration)

ACID + BASE…. of EQUAL parts!

What is the concentration of a hydrochloric acid solution if 50.0mL of a 0.250 M KOH are needed to neutralize 20.0 mL of the HCl solution of unknown concentration?

Base = MolarityBase = VolumeBase =

Acid = MolarityAcid = VolumeAcid =

Formula: MAVA = MBVB MA (20.0mL) = (0.250M)(50.0mL)

MA = (0.250M)(50.0mL)

(20.0mL)

KOH

Acid-‐Base TitraGons

0.250M 50.0mL

HCl …?? 20.0mL

MA = 0.625 M

What is the concentration of a sulfuric acid solution if 50.mL of a 0.25 M KOH are needed to neutralize 20. mL of the H2SO4 solution of unknown concentration?

Base = MolarityBase = VolumeBase =

Acid = MolarityAcid = VolumeAcid =

Formula: MAVA = MBVB MA (20.mL) = (0.25M)(50.mL)

MA = (0.25M)(50.mL)

(20.mL)

KOH


0.25M 50.mL

H2SO4 …?? 20.mL

MA = 0.625 M…but, H2SO4 has 2H+ for every 1 mole, so take:

� à 0.625M/2 = 0.31M

We’ve already concluded that…

�  Arrhenius Acids = H+

�  so, amount of ACID = amount of… MONOprotic Acids:

ex) HCl à H+ molarity = acid solution molarity

�  2.5 M HCl = H+

Diprotic Acids:

ex) H2SO4 à H+ molarity = 2x acid solution molarity �  2.5 M H2SO4 = H+

H+


2.5 M

5.0 M

**Same concept holds true for TRI protic solutions AND bases

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Unit11: Acids,Bases,Salts%josephinesclassroom.weebly.com/uploads/3/8/5/3/38536063/unit_eleven_pdf.pdfUnit11: Acids,Bases,Salts% Essential)Question:)What chemical)propertiesdetermine)