Acid bases and salts (1)

ACIDS, BASES & ACIDS, BASES & SALTSSALTS

Topic 10: ACIDS, BASES & Topic 10: ACIDS, BASES & SALTSSALTS 22

T E R M ST E R M S

ACIDSACIDS are substances that are substances that form hydrogen ionform hydrogen ions (s (HH++(aq)(aq)) )

when dissolved in water when dissolved in water egeg• Hydrochloric acid Hydrochloric acid HClHCl gives gives HH++

(aq)(aq) and C and C l-l-(aq)(aq) ions, ions,

• Sulphuric acid Sulphuric acid HH22SOSO44 gives gives 2H2H++(aq)(aq) and SOand SO44

2-2- ions ions• Nitric acid Nitric acid HNOHNO33 gives gives HH++

(aq)(aq) and NOand NO33--(aq)(aq) ions. ions.

BASESBASES are oxides and hydroxides of metals that are oxides and hydroxides of metals that react react and neutralise acids to form salts and water onlyand neutralise acids to form salts and water only. . Bases which are soluble in water are called alkalisBases which are soluble in water are called alkalis. Not . Not all bases fit into these categories e.g. ammonia. all bases fit into these categories e.g. ammonia.

Alkalis Alkalis are substances that are substances that form hydroxide ions OHform hydroxide ions OH --(aq)(aq) in in

water eg water eg • Sodium Hydroxide Sodium Hydroxide NaOHNaOH gives Na gives Na++

(aq)(aq) and and OHOH--(aq)(aq) ions, ions,

• Calcium Hydroxide Calcium Hydroxide Ca(OH)Ca(OH)22 gives Ca gives Ca2+2+(aq)(aq) and and 2OH2OH--

(aq)(aq) ions. ions.

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In acid solutions there are more H+ ions than OH- ions.

In alkaline solution there are more OH- ions than H+ ions.

Acids that dissociate (ionize) to a large extent are strong electrolytes and Strong Acids.

Acids that dissociate only to a small extent are Weak Acids and weak electrolytes

Bases can be strong or weak depending on the extent to which they dissociate and produce OH– ions in solution. Most metal hydroxides are strong electrolytes and Strong Bases. Ammonia, NH3, is a weak electrolyte and Weak Base.



Basicity of AcidBasicity of Acid

It is the number of ionizable H+ ions present in an acid e.g.

HCl is mono basic, it ionizes to produce one H+ ion

HCl ============== H+ + Cl-

H2SO4 is Dibasic, It ionizes to produce two H+ ions. H2SO4 =============== 2H+ + SO4

2-

H3PO4 is Tribasic, it ionizes to produce three H+ ions. H3PO4 ============== 3H+ + PO4

3-



Acidity of a BaseAcidity of a Base

It is the ionizable OHIt is the ionizable OH -- ions present in an ions present in an alkali. e.g.alkali. e.g.

NaOH is monoacidicNaOH is monoacidic NaOH NaOH ==================== Na Na++ + OH + OH --

Ca(OH)Ca(OH)22 is diacidic is diacidic

Ca(OH)Ca(OH)22 ============================ Ca Ca2+2+ + + 2OH2OH--



Common Strong Acids & their AnionsCommon Strong Acids & their Anions



Common Weak Acids & their AnionsCommon Weak Acids & their Anions


Naming of AcidsNaming of Acids

Binary Acids (HBinary Acids (H++ and a nonmetal) and a nonmetal) hydro (nonmetal) -ide + ic acidhydro (nonmetal) -ide + ic acid

• HCl (aq) = hydrochloric acidHCl (aq) = hydrochloric acid Ternary Acids (HTernary Acids (H++ and a polyatomic ion) and a polyatomic ion)

(polyatomic ion) -ate +ic acid(polyatomic ion) -ate +ic acid

• HNOHNO33 (aq) = nitric acid (aq) = nitric acid (polyatomic ion) -ide +ic acid(polyatomic ion) -ide +ic acid

• HCN (aq) = cyanic acidHCN (aq) = cyanic acid (polyatomic ion) -ite +ous acid(polyatomic ion) -ite +ous acid

• HNOHNO22 (aq) = nitrous acid (aq) = nitrous acid

جمعہ6مارچ2015چچچچ, چ, چچچ چ جمعہ6مارچ2015چچچچ, چ, چچچ چ Topic 10: ACIDS, BASES & Topic 10: ACIDS, BASES &

SALTSSALTS 88

Formula Writing of AcidsFormula Writing of Acids

Acids formulas get written like any other. Write the Acids formulas get written like any other. Write the HH+1+1 first, then figure out what the negative ion is based first, then figure out what the negative ion is based on the name. Cancel out the charges to write the on the name. Cancel out the charges to write the formula. Don’t forget the (aq) after it…it’s only an formula. Don’t forget the (aq) after it…it’s only an acid if it’s in water!acid if it’s in water!

Carbonic acid: HCarbonic acid: H+1+1 and CO and CO33-2-2 = H = H22COCO33 (aq) (aq)

Chlorous acid: HChlorous acid: H+1+1 and ClO and ClO22-1-1 = HClO = HClO22 (aq) (aq)

Hydrobromic acid: HHydrobromic acid: H+1+1 and Br and Br -1-1 = HBr (aq) = HBr (aq) Hydronitric acid:Hydronitric acid:


SALTSSALTS 99

Properties of BasesProperties of Bases

Bases react with fats to form soap and glycerol. This Bases react with fats to form soap and glycerol. This process is called saponification. process is called saponification.

Bases have a pH of more than 7.Bases have a pH of more than 7. Dilute solutions of bases taste bitter.Dilute solutions of bases taste bitter. Bases turn phenolphthalein PINK, litmus BLUE and Bases turn phenolphthalein PINK, litmus BLUE and

bromthymol blue BLUE.bromthymol blue BLUE. Bases neutralize acids.Bases neutralize acids. Bases are formed when alkali metals or alkaline earth Bases are formed when alkali metals or alkaline earth

metals react with water. The words “alkali” and “alkaline” metals react with water. The words “alkali” and “alkaline” mean “basic”, as opposed to “acidic”.mean “basic”, as opposed to “acidic”.


SALTSSALTS 1010

Topic 10: ACIDS, BASES & SALTSTopic 10: ACIDS, BASES & SALTS

Naming of BasesNaming of Bases

Bases are named like any ionic Bases are named like any ionic compound, the name of the metal compound, the name of the metal ion first (with a Roman numeral if ion first (with a Roman numeral if necessary) followed by necessary) followed by “hydroxide”.“hydroxide”.Fe(OH)2 (aq) = iron (II) hydroxide

Fe(OH)3 (aq) = iron (III) hydroxide

Al(OH)3 (aq) = aluminum hydroxide

NH3 (aq) is the same thing as NH4OH:

NH3 + H2O → NH4OH

Also called ammonium hydroxide.جمعہ6مارچ2015چچچچ, چ, چچچ چ جمعہ6مارچ2015چچچچ, چ, چچچ چ 1111

Topic 10: ACIDS, BASES & SALTSTopic 10: ACIDS, BASES & SALTS

Formula Writing of BasesFormula Writing of Bases

Formula writing of bases is the same as for any ionic Formula writing of bases is the same as for any ionic formula writing. The charges of the ions have to cancel formula writing. The charges of the ions have to cancel out.out.

Calcium hydroxide = CaCalcium hydroxide = Ca+2+2 and OH and OH-1-1 = Ca(OH) = Ca(OH)22 (aq) (aq)

Potassium hydroxide = KPotassium hydroxide = K+1+1 and OH and OH-1-1 = KOH (aq) = KOH (aq) Lead (II) hydroxide = PbLead (II) hydroxide = Pb+2+2 and OH and OH-1-1 = Pb(OH) = Pb(OH)22 (aq) (aq)

Lead (IV) hydroxide = PbLead (IV) hydroxide = Pb+4+4 and OH and OH-1-1 = Pb(OH) = Pb(OH)44 (aq) (aq)

Lithium hydroxide =Lithium hydroxide = Copper (II) hydroxide =Copper (II) hydroxide = Magnesium hydroxide =Magnesium hydroxide =

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Physical Properties of Acids & BasesPhysical Properties of Acids & Bases ACIDSACIDS Acids taste sour (e.g. vinegar, lemon juice).Acids taste sour (e.g. vinegar, lemon juice). Acids are harmful to living cells.Acids are harmful to living cells. Aqueous solutions of all acids contain hydrogen ions.Aqueous solutions of all acids contain hydrogen ions. Acid turns blue litmus red.Acid turns blue litmus red. Strong acids are corrosive.Strong acids are corrosive.

BASESBASES Alkalis are taste bitterAlkalis are taste bitter Strong alkalis are corrosive.Strong alkalis are corrosive. Aqueous solutions of all alkalis contain hydroxide ion.Aqueous solutions of all alkalis contain hydroxide ion. Alkalis turns red litmus blue.Alkalis turns red litmus blue. Soapy touch.Soapy touch.



Chemical Properties of AcidsChemical Properties of Acids

With metalsWith metals Metals above copper in the reactivity series will Metals above copper in the reactivity series will

react with acids, giving off hydrogen gas, forming a react with acids, giving off hydrogen gas, forming a saltsalt..

MgMg(s)(s) + H + H22SOSO4(aq)4(aq) →→ MgSO MgSO4(aq)4(aq) + H + H2(g)2(g)

With bases (metal oxides and hydroxides)With bases (metal oxides and hydroxides) The base dissolves in the acid and neutralises it. A The base dissolves in the acid and neutralises it. A

salt is formed.salt is formed. HH22SOSO4(aq)4(aq) + CuO + CuO(s)(s) →→ CuSO CuSO4(aq)4(aq) + H + H22OO(l)(l)

With metal carbonatesWith metal carbonates With metal carbonates, effervescence occurs, salt, With metal carbonates, effervescence occurs, salt,

water and carbon dioxide gas is produced.water and carbon dioxide gas is produced. 2HCl2HCl(aq)(aq) + CaCO + CaCO3(s)3(s) →→ CaCl CaCl2(s) 2(s) + H+ H22OO(l)(l) + CO + CO2(g)2(g)


NeutralizationNeutralization

HH+1+1 + OH + OH-1-1 →→ HOHHOH

Acid + Base Acid + Base →→ Water + Salt (double replacement)Water + Salt (double replacement)

HCl (aq) + NaOH (aq) HCl (aq) + NaOH (aq) →→ HOH (l) + NaCl (aq) HOH (l) + NaCl (aq)

HH22SOSO44 (aq) + KOH (aq) (aq) + KOH (aq) →→ 2 HOH (l) + K2 HOH (l) + K22SOSO44 (aq) (aq)

HBr (aq) + LiOH (aq) HBr (aq) + LiOH (aq) →→ HH22CrOCrO44 (aq) + NaOH (aq) (aq) + NaOH (aq) →→ HNOHNO33 (aq) + Ca(OH) (aq) + Ca(OH)22 (aq) (aq) →→ HH33POPO44 (aq) + Mg(OH) (aq) + Mg(OH)22 (aq) (aq) →→


SALTSSALTS 1515


Formation of Hydronium ion( HFormation of Hydronium ion( H3300++).).

The hydrogen ion HThe hydrogen ion H++(aq)(aq) does not exist as such in aqueous does not exist as such in aqueous

solutions. Hydrogen ions combine with water molecules solutions. Hydrogen ions combine with water molecules to give a more stable species, the to give a more stable species, the hydronium ion Hhydronium ion H33OO

++..

HClHCl(aq)(aq) + H + H22OO(l) < =========(l) < ========= H H33OO++(aq)(aq) + Cl + Cl--

(aq)(aq)

Acids can contain different numbers of acidic hydrogens, Acids can contain different numbers of acidic hydrogens, and can yield different numbers of Hand can yield different numbers of H33OO++ ions in solution. ions in solution.



USES OF ACIDSUSES OF ACIDS HCl in stomachHCl in stomach

HH22SOSO44 in car batteries, as drying agent’ in car batteries, as drying agent’

HNOHNO33 in manufacturing of fertilizers in manufacturing of fertilizers

Ethanoic acid in food industryEthanoic acid in food industry

Fatty acids in soap makingFatty acids in soap making

Ascorbic acid in medicineAscorbic acid in medicineجمعہ6مارچ2015چچچچ, چ, چچچ چ جمعہ6مارچ2015چچچچ, چ, چچچ چ


Chemical Properties of BasesChemical Properties of Bases NeutralisationNeutralisation. .

Ammonium salts are decomposed when mixed Ammonium salts are decomposed when mixed with a basewith a base eg sodium hydroxide. The ammonia is eg sodium hydroxide. The ammonia is readily detected by its pungent odour (strong smell) readily detected by its pungent odour (strong smell) and by turning damp red litmus blue. and by turning damp red litmus blue.

NaOH + NHNaOH + NH44Cl ==> NaCl + HCl ==> NaCl + H22O + NHO + NH33 Ionically: Ionically: NHNH44

++ + OH + OH-- ==> H ==> H22O + NHO + NH33

This reaction can be used to prepare ammonia gas This reaction can be used to prepare ammonia gas and as a test for an ammonium salt. and as a test for an ammonium salt.



Chemical Properties of BasesChemical Properties of Bases

Alkali's are used to produce the insoluble Alkali's are used to produce the insoluble hydroxide precipitates of many metal ionshydroxide precipitates of many metal ions from from their soluble salt solutions. their soluble salt solutions.

2NaOH2NaOH(aq)(aq) + CuSO + CuSO4(aq) 4(aq) ==> Na==> Na22SOSO4(aq)4(aq) + Cu(OH) + Cu(OH)2(s)2(s)

ionically: ionically: CuCu2+2+(aq)(aq) + 2OH + 2OH--

(aq)(aq) ==> Cu(OH) ==> Cu(OH)2(s)2(s)

This reaction can be used as a simple test to help This reaction can be used as a simple test to help

identify certain metal ions. identify certain metal ions.



TYPES OF OXIDESTYPES OF OXIDES ::

• BASIC OXIDESBASIC OXIDES• On the left and middle of the Periodic Table are the On the left and middle of the Periodic Table are the

basic metal oxidesbasic metal oxides eg Na eg Na22O, MgO, CuO etcO, MgO, CuO etc• They react with acids to form salts. e.g They react with acids to form salts. e.g

• 2HCl + MgO ------------2HCl + MgO ------------ MgCl MgCl22 + H + H22OO

• CuO + HCuO + H22SOSO44 ------------- ------------- CuSO CuSO44 + H + H22OO•

• These These metal oxidesmetal oxides tend to be ionic in bonding tend to be ionic in bonding character with high melting points. character with high melting points.

• As you move left to right the oxides become less As you move left to right the oxides become less basic and more acidic.basic and more acidic.



TYPES OF OXIDESTYPES OF OXIDES

• ACIDIC OXIDES:ACIDIC OXIDES: On the right of the Periodic On the right of the Periodic Table the Table the acidic oxides of the non-metalsacidic oxides of the non-metals are are present e.g. COpresent e.g. CO22, P, P22OO55, SO, SO22, SO, SO33 etc. etc.

• These tend to be covalent in bonding character These tend to be covalent in bonding character with low melting/boiling points.with low melting/boiling points.

• Those of sulphur and phosphorus are very soluble Those of sulphur and phosphorus are very soluble in water to give acidic solutions which can be in water to give acidic solutions which can be neutralised by alkalis to form salts. neutralised by alkalis to form salts.

• SOSO22 + H + H22O -----------O ----------- H H22SOSO33

• SOSO33 + H + H22O -----------O ----------- H H22SOSO44




AMPHOTERIC OXIDES:AMPHOTERIC OXIDES: They are metallic oxides.They are metallic oxides.

They react with both acids and alkalis. They react with both acids and alkalis.

They are usually relatively insoluble and have little They are usually relatively insoluble and have little effect on indicators.effect on indicators.

An example is aluminium oxide dissolves in acids An example is aluminium oxide dissolves in acids to form 'normal' aluminium salts like the chloride, to form 'normal' aluminium salts like the chloride, sulphate and nitrate. However, it also dissolves in sulphate and nitrate. However, it also dissolves in strong alkali's like sodium hydroxide solution to strong alkali's like sodium hydroxide solution to form 'aluminate' salts. form 'aluminate' salts.




• NEUTRAL OXIDES:NEUTRAL OXIDES:• They are non- metallic oxides.They are non- metallic oxides.• They tend to be of low solubility in water and They tend to be of low solubility in water and

have no effect on litmus.have no effect on litmus.• do not react with acids or alkalis. eg CO do not react with acids or alkalis. eg CO

carbon monoxide and NO nitrogen monoxide, carbon monoxide and NO nitrogen monoxide, HH22O. O.

• There is no way of simply predicting this kind There is no way of simply predicting this kind of behavior from periodic table patterns! of behavior from periodic table patterns!



PERIODIC TRENDS IN OXIDES PERIODIC TRENDS IN OXIDES



SALTSSALTS

When When HH++ ion of an acid is replaced by a metal ion, a ion of an acid is replaced by a metal ion, a salt is produced e.g. salt is produced e.g.

HH22SOSO4(aq)4(aq) + 2NaOH + 2NaOH(aq)(aq) ============ Na Na22SOSO4(aq)4(aq) + + 2H2H22OO(l)(l)

Here sodium sulphate (NaHere sodium sulphate (Na22SOSO44) is the salt formed. ) is the salt formed. Salts are ionic compounds. Salts are ionic compounds.

Note: Ammonia (NHNote: Ammonia (NH33) is an unusual base - it does ) is an unusual base - it does not contain a metal. It forms not contain a metal. It forms ammoniumammonium saltssalts, , containing the ammonium ion, NHcontaining the ammonium ion, NH44

++.. e.g.e.g. NHNH3(aq)3(aq) + HNO + HNO3(aq) 3(aq) →→ NHNH44NONO3(aq)3(aq)

(ammonium nitrate)(ammonium nitrate)جمعہ6مارچ2015چچچچ, چ, چچچ چ جمعہ6مارچ2015چچچچ, چ, چچچ چ


Methods of making Soluble Methods of making Soluble SaltsSalts

1)1) ACID + METALACID + METAL →→ SALT + HYDROGENSALT + HYDROGEN

2)2) ACID + BASE ACID + BASE →→ SALT + WATER SALT + WATER

3)3) ACID + CARBONATE ACID + CARBONATE →→ SALT + WATER + SALT + WATER + CARBON CARBON DIOXIDEDIOXIDE

4)4) ACID + ALKALIACID + ALKALI →→ SALT + WATER SALT + WATER

5)5) DIRECT COMBINATIONDIRECT COMBINATION



Method 1 (Acid + Metal) Method 1 (Acid + Metal) Not suitable for making salts of metals Not suitable for making salts of metals aboveabove

magnesium, or magnesium, or belowbelow iron/tin in reactivity. iron/tin in reactivity. e.g.e.g.

• Zn + 2HCl -------------------Zn + 2HCl ------------------- ZnCl ZnCl22 + H + H22

• Fe + HFe + H22SOSO4 4 ---------------- ---------------- FeSO FeSO44 + H + H22

Method 2 (Acid + Base)Method 2 (Acid + Base) Useful for making salts of less reactive metals, Useful for making salts of less reactive metals,

e.g. lead, copper.e.g. lead, copper. e.g. e.g.

• CuO + HCuO + H22SOSO44 ---------------- ---------------- CuSO CuSO44 + H + H22OO

• MgO + 2HCl ------------------MgO + 2HCl ------------------ MgCl MgCl22 + H + H22OO

Add excess base to acid. Add excess base to acid.



Method 3 (Acid + Carbonate)Method 3 (Acid + Carbonate) Useful particularly for making salts of more reactive Useful particularly for making salts of more reactive

metals, e.g. calcium, sodium.metals, e.g. calcium, sodium. e.g.e.g.

• CaCOCaCO3 3 + 2HCl ------------- + 2HCl ------------- CaCl CaCl22 + H + H22O + COO + CO22..• NaNa22COCO33 + H + H22SOSO44 ------------ ------------ Na Na22SOSO4 4 + H + H22O + COO + CO22..

Method 4 (Acid + Alkali)Method 4 (Acid + Alkali) This is useful for making salts of reactive metals, and This is useful for making salts of reactive metals, and

ammonium salts. It is different from methods 1-3, as ammonium salts. It is different from methods 1-3, as both reactants are in solution. This means neutralisation both reactants are in solution. This means neutralisation must be achieved, by adding exactly the right amount of must be achieved, by adding exactly the right amount of acid to neutralise the alkali. This can be worked out by acid to neutralise the alkali. This can be worked out by titrationtitration

e.g.e.g.• NaOH + HCl --------------NaOH + HCl -------------- NaCl + H NaCl + H22OO• 2NH2NH44OH + HOH + H22SOSO44 ---------------------- ---------------------- (NH (NH44))22SOSO44 + 2H + 2H22OO


Topic 10: ACIDS, BASES & Topic 10: ACIDS, BASES & SALTSSALTS جمعہ6مارچ2015چچچچ, چ, چچچ چ 2929 جمعہ6مارچ2015چچچچ, چ, چچچ چ


Making Insoluble SaltsMaking Insoluble Salts

This involves mixing solutions of two This involves mixing solutions of two solublesoluble salts that between them contain the ions that salts that between them contain the ions that make up the insoluble salt. It is made by two make up the insoluble salt. It is made by two methods.methods. PRECIPITATIONPRECIPITATION

• BaClBaCl2(aq)2(aq) + MgSO + MgSO4(aq)4(aq) →→ BaSO BaSO4(s) 4(s) + MgCl+ MgCl2(aq)2(aq)

DIRECT COMBINATIONDIRECT COMBINATION• Fe + S ---heat----Fe + S ---heat---- FeS FeS



PRECIPITATION REACTIONPRECIPITATION REACTION



Types of SaltsTypes of Salts

Normal Salts:Normal Salts: Normal salts are formed when all the Normal salts are formed when all the

replaceable hydrogen ions in the acid have replaceable hydrogen ions in the acid have been completely replaced by metallic ions.been completely replaced by metallic ions.

HClHCl(aq)(aq) + NaOH + NaOH(aq)(aq) →→ NaCl NaCl(aq)(aq) + + HH22OO(l) (l)

HH22SOSO4(aq)4(aq) + ZnO + ZnO(aq)(aq) →→ ZnSO ZnSO4(aq)4(aq) + H + H22OO(l) (l)

Normal salts are neutral to litmus paper.Normal salts are neutral to litmus paper.



Acid salts:Acid salts: Acid salts are formed when replaceable hydrogen ions in Acid salts are formed when replaceable hydrogen ions in

acids are only partially replaced by a metal. Acid salts acids are only partially replaced by a metal. Acid salts are produced only by acids containing more then one are produced only by acids containing more then one replaceable hydrogen ion. Therefore an acid with two replaceable hydrogen ion. Therefore an acid with two replaceable ions e.g. Hreplaceable ions e.g. H22SOSO44 will form only one acid salt, will form only one acid salt, while acid with three replaceable hydrogen ions e.g. while acid with three replaceable hydrogen ions e.g. HH33POPO44 will form two different acid salts. will form two different acid salts.

HH22SOSO4(aq)4(aq) + KOH + KOH (aq)(aq) →→ KHSO KHSO4(aq) 4(aq) + H + H22OO(l)(l)

HH33POPO4(aq)4(aq) + NaOH + NaOH →→ NaH NaH22POPO4(aq) 4(aq) + H + H22OO(l)(l)

HH33POPO4(aq) 4(aq) + 2NaOH + 2NaOH (aq)(aq) →→ Na Na22HPOHPO4(aq) 4(aq) + 2H + 2H22OO(l)(l)

An acid salt will turn blue litmus red. In the presence of An acid salt will turn blue litmus red. In the presence of excess metallic ions an acid salt will be converted into a excess metallic ions an acid salt will be converted into a normal salt as its replaceable hydrogen ions become normal salt as its replaceable hydrogen ions become replaced.replaced.

KHSOKHSO4(aq)4(aq) + KOH + KOH ================================ K K22SOSO4(aq)4(aq) + H+O + H+O (l)(l) جمعہ6مارچ2015چچچچ, چ, چچچ چ جمعہ6مارچ2015چچچچ, چ, چچچ چ


Basic Salts:Basic Salts: Basic salts contain the hydroxide ion, OH-. They are Basic salts contain the hydroxide ion, OH-. They are

formed when there is insufficient supply of acid for the formed when there is insufficient supply of acid for the complete neutralization of the base. A basic salt will complete neutralization of the base. A basic salt will turn red litmus blue and will react with excess acid to turn red litmus blue and will react with excess acid to form normal salt.form normal salt.

Zn(OH)Zn(OH)2(s) 2(s) + HCl + HCl(aq)(aq) →→ Zn(OH)Cl Zn(OH)Cl (aq)(aq) + H + H22OO(l)(l)

Zn(OH)ClZn(OH)Cl(aq)(aq) + HCl + HCl (aq)(aq) →→ ZnCl ZnCl2(aq)2(aq) + H + H22OO(l)(l)

Mg(OH)Mg(OH)2(s)2(s) + HNO + HNO3(aq)3(aq) →→ Mg(OH)NO Mg(OH)NO3(aq)3(aq) + H + H22OO(l)(l)

Mg(OH)NOMg(OH)NO3(aq) 3(aq) + HNO + HNO3(aq)3(aq) →→ Mg(NO Mg(NO33))2(aq)2(aq) + H + H22OO(l) (l)



HYDRATED & ANHYDROUS SALTSHYDRATED & ANHYDROUS SALTS

Hydrated Salt: Salt that contains Water of Hydrated Salt: Salt that contains Water of Crystallization is called Hydrated Salt e.g. Crystallization is called Hydrated Salt e.g. CuSOCuSO44.5H.5H22O, NaO, Na22COCO33.10H.10H22O.O.

Anhydrous Salt: Salt with out Water of Anhydrous Salt: Salt with out Water of Crystallization is called Anhydrous Salt. e.g. Crystallization is called Anhydrous Salt. e.g. CuSOCuSO4, 4, NaNa22COCO33



USES OF SALTSUSES OF SALTSS.No

.SALT USE

1 Ammonium Chloride In torch batteries

2 Ammonium Nitrate In fertilizers

3 Calcium Chloride As drying agent

4 Iron Sulphate In Iron tablets

5 Magnesium Sulphate In medicine

6 Potassium Nitrate In gunpowder etc.

7 Silver Bromide In photography

8 Sodium Chloride Making NaOH

9 Sodium Stearate In making soap.



Self Ionization of WaterSelf Ionization of Water

Pure water is often used as an example of non- Pure water is often used as an example of non- conducting liquid. In fact water will conduct electricity if conducting liquid. In fact water will conduct electricity if there is sufficient electrical energy present. The fact that there is sufficient electrical energy present. The fact that pure water conduct electricity suggest that it contains pure water conduct electricity suggest that it contains ions. The ions present are due to water undergoing self ions. The ions present are due to water undergoing self ionization.ionization.

2H2H22OO(l)(l) ==================== H H33OO++(aq)(aq) + OH + OH-- (aq)(aq)

The concentration of HThe concentration of H33OO++ ions in pure water at 25 ions in pure water at 25ooC is C is 1010-7-7 moles/dm moles/dm33. The concentration of OH. The concentration of OH -- ion should also ion should also be 10be 10-7-7 moles/dm moles/dm33..



The pH ScaleThe pH Scale



The The pH scalepH scale is a measure of the relative acidity or is a measure of the relative acidity or alkalinity of a solution. alkalinity of a solution.

It is defined as negative log of HIt is defined as negative log of H++ ion concentration. ion concentration. pH = -log [HpH = -log [H++]]

Water is a neutral liquidWater is a neutral liquid with a pH of 7 (green). When a with a pH of 7 (green). When a substance dissolves in water it forms an aqueous substance dissolves in water it forms an aqueous solution that may be acidic, neutral or alkaline. solution that may be acidic, neutral or alkaline.

Acidic solutions have a pH of less than 7Acidic solutions have a pH of less than 7, and the , and the lower the number, the stronger the acid is.. lower the number, the stronger the acid is..

Neutral solutions have a pH of 7Neutral solutions have a pH of 7. These are quite often . These are quite often solutions of salts, which are themselves formed from solutions of salts, which are themselves formed from neutralizingneutralizing acids and bases. acids and bases.

Alkaline solutions have a pH of over 7Alkaline solutions have a pH of over 7 and the higher and the higher the pH the stronger is the alkali. the pH the stronger is the alkali. Weak alkalis Weak alkalis like like ammonia give a pH of 10-11 but ammonia give a pH of 10-11 but strong alkalis strong alkalis like like sodium hydroxide give a pH of 13-14. sodium hydroxide give a pH of 13-14.


pHpH

A change of 1 in pH is a tenfold increase in acid or base A change of 1 in pH is a tenfold increase in acid or base strength.strength.

A pH of 4 is 10 times more acidic than a pH of 5.A pH of 4 is 10 times more acidic than a pH of 5. A pH of 12 is 100 times more basic than a pH of 10.A pH of 12 is 100 times more basic than a pH of 10.


SALTSSALTS 4141


INDICATORS.INDICATORS.

S.No.S.No. IndicatorIndicator Color in strong Color in strong acidic solutionacidic solution

pH at which pH at which color changecolor change

Color in strong Color in strong alkaline solutionalkaline solution

11 Methyle Methyle orangeorange

RedRed 44 YellowYellow

22 BromothymoBromothymol bluel blue

YellowYellow 77 BlueBlue

33 PhenolphthaPhenolphthaleinlein

ColorlessColorless 99 RedRed

44 Screened Screened methyl methyl orangeorange

RedRed 44 GreenGreen

•Indicators are the substances that have different colors in acidic and in alkaline solution.



pH GraphpH Graph



IONIC EQUATIONS IONIC EQUATIONS In many reactions only certain ions change their In many reactions only certain ions change their 'chemical state' but other ions remain in exactly the 'chemical state' but other ions remain in exactly the same original physical and chemical state.same original physical and chemical state.

The ions that do not change are calledThe ions that do not change are called 'spectator ions'. 'spectator ions'. The ionic equation represents the 'actual' chemical The ionic equation represents the 'actual' chemical

change and omits the spectator ions.change and omits the spectator ions. To write a net ionic equation:To write a net ionic equation:

• Write a balanced molecular equation. Write a balanced molecular equation.

• Rewrite the equation showing the ions that form in solution when Rewrite the equation showing the ions that form in solution when each soluble electrolyte dissociates into its component ions. Only each soluble electrolyte dissociates into its component ions. Only dissolved strong electrolytes are written in ionic form.dissolved strong electrolytes are written in ionic form.

• Identify and cancel the spectator ions that occur unchanged on both Identify and cancel the spectator ions that occur unchanged on both sides of the equation. sides of the equation.

• Write correct state symbols.Write correct state symbols.



SCHEME FOR IONIC EQUATIONSCHEME FOR IONIC EQUATION



THE ENDTHE END


Acid bases and salts (1)

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