Acids bases and salts

• An acid is a compound which when dissolved in water produces hydrogen ions (H+ (aq)) HYDROGEN ION IS THE ONLY POSITIVELY CHARGED ION
• Examples of acids are

  Hydrochloric acid Hcl. cancel each other because its H+ and CL-

  Nitric acid Hno3 H+ and No3-

  Sulfuric acid H2So4 2H+ and So4 2-
• A strong acid is a compound which when added to water it undergoes 100% dissociation/ionisation


  example: Hydrogen chloride HCL is 100% covalent. On adding HCL to water, HCL will undergo complete dissociation. This is, it completley changes bonding from 100% covalent to 100% electrovalent. Then after dissociation it is called hydrochloric acid
• Other strong acids are Nitric acid (HNO3), Sulfuric acid (H2SO4), Phosphoric acid (H3PO4)
• A weak acid is s substance when dissolved in water only undergoes partial dissociation.


  Example:

  Glarical ethanoic acid (vinegar CH3COOH) is 100% covalent. On adding ethanoic acid to water, ethanoic acid only undergoes partial ionisation. That is out of 1000 molecules of ethanoic acid only 4 molecules ionise (0.04%)

  CH3COOH (l) <--> CH3COO- (aq) + H+ (aq)
• Ionise means to go from covalent to ionic
• Other weak acids are Carbonic acid (H2Co3) and Sulfurous acid (H2So3)
• A concentrated acid is a substance which contains a high amount od acid and a small amount of water 


  A dilute acid is a substance which contains a small amount of acid and a high amount of water
• The basicity of the acid is the number of hydrogen ions (H+(aq) present in every acid molecule 


  Name of acid Formula of acid Baseicity

  Hydrochloric acid HCL Monobasic

  Nitric acid HNO3 Monobasic

  sulfuric aid H2SO4 Dibasic

  Phosphoric acid H3PO4 Tribasic

  Ethanoric acid CH3COOH Monobasic
• Physical properties of acids are that acids have a sour taste, acids change blue litmus paper to red and lastly acids are corrosive, they have a burning sensation
• There are six chemical properties of acids. One of which is that metals react acids. All metals which are found above hydrogen in the electrochemical series (e.c.s) will react with acids to produce salt and hydrogen. This reaction is called displacement. 


  Electrochemical series

  k+1

  Na+1

  Ca2+

  Mg2+

  Al3+

  Zn2+

  Fe2+/ Fe3+

  Pb2+

  H+1

  Ca2+

  Ag+1
• Example of a metal reacting with an acid:

  0 +1 +2 -1 0

  Mg (S) + 2Hcl (AQ) --> Mgcl2 (AQ) +H2 (G)

  Metal + dilute acid --> salt + Hydrogen 


  Half equation

  Mg0-2e- --> mg+2 mg0 -> 12 protons pro> ele

  (H+ + le- --> H0) x2 12 electrons =

  2H+1 +2e- --> H20 mg+2 -> 12 protons +

  10 electrons

  Ionic equation

  mg0 (s) + 2H+ (aq) --> mg+2 (aq) + H20 (g)
• Another example of a metal reacting with an acid

  0 +1 -1 +2 -1 0

  Zn (s) + 2Hcl (aq) --> ZnCl2 (aq) + H2 (g)

  Half equation

  Zn0 - 2e- --> Zn+2

  (H+1 + 1e- --> H0) x2

  2H+1 + 2e- --> H20


  Valency -> amount of electrons being lost or gained

  + because protons are winning

  2 because there are 2 more protons

  x2 because it is diatomic

  -to show that they are negatively charged

  0 because protons and electrons are equal
• Another chemical property of acid is that metal oxides react with dilute acids

  All metal oxides react with dilute acids to produce salt and water. This reaction is called neutralisation
• Example of a metal oxide reacting with dilute acid

  mgo (s) + 2Hcl (aq) --> mgcl2 (aq) +h2o (l)

  metal oxide + dilute acid --> salt + water

  Ionic equation

  O2- (s) + 2H+ (aq) --> H2o (l)
• A chemical property of an acid is that metal hydroxides react with dilute acids

  All metal hydroxides react with dilute acids to produce a salt and water. This reaction is called neutralisim
• An example of a metal hydroxide reacting with a dilute acid

  NaOh (aq) + Hcl (aq) --> NaCl (aq) + H2o (l)

  metal oxide + dilute acid --> salt + water

  Ionic equation

  Oh- (aq) + H+ (aq) --> H2O (l)
• A chemical property of acids is that metal carbonates react with dilute acids. All metal carbonates react with dilute acids to produce a salt, water and carbon dioxide gas. 


  :)
• Example of a metal carbonate reacting with a dilute acid

  Na2Co3 (s)+ Hcl (aq) --> NaCl (aq) + H2O (l) + Co2 (g)

  metal carbonate + dilute acid -> salt+ water + carbon dioxide 


  Ionic equation

  Co3 2- (s) + 2H- (aq) --> H2O (l) + Co2 (g)
• A chemical property of an acid is that metal hydrogen carbonate reacts with dilute acids 


  All metal hydrogen carbonates react with dilute acids to produce salt, water and carbon dioxide gas
• Example of a metal hydrogen carbonate reacting with a dilute acid.

  NaHCo3 (s) + HCl (aq) --> NaCl (aq) + H2O (l) + Co2 (g)

  metal hydrogen carbonate + dilute acid --> salt + water + Co2


  Ionic equation

  Hco3- (s) + H+ (aq) --> H2O (l) + Co2 (g)
• Another chemical property of a metal is that Metal sulfates react with dilute acids 


  All metal sulfates react with dilute acids to produce a salt< water and sulfur dioxide gas
• An example of a metal reacting with a dilute acid is

  K2So3 (s) + 2Hcl (aq) --> 2Kcl (aq) + H2o (l) So2 (g)

  metal sulfate + dilute acid --> salt + water + sulfur dioxide gas

  Ionic equation

  So3 2- (s) 2H+ (aq) --> H2O (l) So2 (g)
• Note! Never add salt in ionic equations
• A base is a substance which can combine with hydrogen (H+) ions from the acid to produce a salt and water

  
  

  A base has either oxide (o2-) or hydroxide (OH-) ions
• Base example

  mgO () + 2HCl () --> MgCl2 () + H2O

  metal oxide dilute acid --> salt and water 


  Ionic equation

  O2- (s) + 2H+ (aq) --> H2O (l)
• Classification of metal oxides:

  Bases can be either metal oxides or metal hydroxides 


  Metal oxides:

  Metal oxides are compounds produced between metal ions and oxide (O2-) ions.

  Metal oxides can be soluble or insoluble
• Insoluble metal hydroxides are all other

  metal hydroxides
• An alkali is a basic metal hydroxide that has soluble hydroxide (OH-) ion
• Physical properties of an alkali are that alkalis have a bitter taste, they change litmus paper to blue and that alkalis are caustic, that is that they cause damage to tissues
• A chemical property of an alkali is that Alkali react with acids to produce a salt and water. This is called neutralism


  Example:

  NaOH (aq) + Hcl (aq) --> NaCl (aq) + H2O (l)

  Alkali Dilute acid salt water
• All group 1 metal oxides and group 2 metals from calcium downwards are soluble


  Everything else is insoluble
• A metal hydroxide is made up from a metallic ion and hydroxide (O+1-) ions 


  Metal hydroxide can be soluble and insoluble
• All group one metal hydroxides and group 2 metal hydroxides from calcium downwards are soluble

  Ionic equation

  OH- (aq) + H+ (aq) --H2O (l)
• A salt is a substance formed when metallic ions displace hydrogen (H+(aq) ions of the acid 


  Acid Salt

  Hydrochloric acid (HCl) Sodium chloride (NaCl)

  Nitric acid (HNo3) Potassium nitrate (KNo3)

  Sulfuric acid (H2So4) Magnesium sulfate (mgSo4)
• There are two types of salts:

  Normal salts

  Acid salts
• A normal salt is obtained when all hydrogen (H+(aq) ions are displaced by metallic ions 


  Acid salts Normal salts

  Hydrochloric acid (HCl) Potassium chloride (KCl)

  Nitric acid (HNO3) Sodium nitrate (NaNo3)

  Sulfuric acid (H2So4) Calcium sulfate (CaSo4)
• All normal salts are neutral 


  and normal salts can be either soluble or insoluble
• An acid salt is a substance produced when some of the hydrogen (H+(aq) ions are displaced by metallic ions 


  Acids Acid salt Normal salt

  Sulfuric acid (H2So4) Potassium hydrogen Potassium sulfate

  sulfate (KHSo4) (K2SO4)

  Carbonic acid (H2Co3) Sodium hydrogen Sodium carbonate

  Carbonate (NaHCo3) (Na2CO3)
• • Acid salts are soluble in water
  • Acid salts are neutral exept sodium hydrogen carbonate (NaHCO3) which is slightly alkaline (pH=8)