ACIDS, BASES & SALTS Ions Some times substances go through a reaction that breaks off a hydrogen or even a hydrogen and an Oxygen. These extra Ions (Charged Particles) are what make up Acids and Bases. H2O -> H+ + OH- Ions Because the Single Hydrogen no longer shares that electron is becomes positively charged. He is now called a Hydrogen Ion. Ions The Oxygen and Hydrogen now have an extra electron and become negatively charged. They are now called a Hydroxide Ion. Acid Any substance that has extra Hydrogen Ions is an acid. The more Hydrogen Ions the more acidic. Basis When a substance has extra hydroxide ions (OH- ) then it is a base. The more hydroxide ions the more basic. (Bases can also be called Alkaline) pH Scale The pH scale was created to better compare the relative concentration of Hydrogen ions. pH stands for partial Hydrogen. The scale ranges from 0 to 14 and each step is a multiple of 10. The scale is logarithmic. pH Example: Urine generally has a pH of 6 where as water has a pH of 7. This means that Urine has 10 times more Hydrogen Ions than water. pH A pH of 7 is considered neutral. This means that there as many Hydrogen ions as there are hydroxide ions. They balance each other out. TERMS ACIDS are substances that form hydrogen ions (H+(aq)) when dissolved in water eg BASES are hydroxides that react and neutralize. In acid solutions there are more H+ ions than OH- ions. In alkaline solution there are more OH- ions than H+ ions. 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 11 Strong or Weak - Acids or Bases that dissociate completely are Strong Acids/Bases. Acids or Bases that dissociate only partially are Weak Acids/Bases 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 12 Physical Properties of Acids & Bases ACIDS Acids taste sour (e.g. vinegar, lemon juice). Acids are harmful to living cells. Aqueous solutions of all acids contain hydrogen ions. Acid turns blue litmus red. Strong acids are corrosive. BASES Alkalis are taste bitter Strong alkalis are corrosive. Aqueous solutions of all alkalis contain hydroxide ion. Alkalis turns red litmus blue. Soapy touch. 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 13 Neutralization H+1 + OH-1 HOH Acid + Base Water + Salt (double replacement) Example: HCl (aq) + NaOH (aq) HOH (l) + NaCl (aq) H2SO4 (aq) + KOH (aq) 2 HOH (l) + K2SO4 (aq) 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 14 SALTS When H+ ion of an acid is replaced by a metal ion, a salt is produced e.g. H2SO4+ 2NaOH====== Na2SO + 2H2O Here sodium sulphate (Na2SO4) is the salt formed. Salts are ionic compounds. 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 15 Methods of making Soluble Salts 1) ACID + METAL SALT + HYDROGEN 2) ACID + BASE SALT + WATER 3) ACID + CARBONATE SALT + WATER + CARBON DIOXIDE 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 16 Types of Salts Normal Salts: Normal salts are formed when all the replaceable hydrogen ions in the acid have been completely replaced by metallic ions. HCl(aq) + NaOH(aq) NaCl(aq) H2SO4(aq) 1444 ، ذو الح ّج16 ،منگل + ZnO(aq) + H2O(l) ZnSO4(aq) + H2O(l) Topic 10: ACIDS, BASES & SALTS 17 Types of Salts Acid salts: Acid salts are formed when replaceable hydrogen ions in acids are only partially replaced by a metal. H2SO4 + KOH KHSO4 + H2O H3PO4 + NaOH NaH2PO4 + 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS H2O 18 Types of Salts Basic Salts: Basic salts contain the hydroxide ion, OH-. They are formed when there is insufficient supply of acid for the complete neutralization of the base. Zn(OH)2 + HCl Zn(OH)Cl + H2O Mg(OH)2 + HNO3 Mg(OH)NO3 + H2O 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 19 USES OF SALTS S.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. 1444 ، ذو الح ّج16 ،منگل Topic 10: ACIDS, BASES & SALTS 20 THE 1444 ، ذو الح ّج16 ،منگل END Topic 10: ACIDS, BASES & SALTS 21