acids and bases

Acids have a pH below 7 They are corrosive and sour tasting In acidic conditions blue litmus paper and methyl orange turns red Acids are proton donors as they ionize in solution producing protons, H+ ions These H+ ions make the aqueous solution acidic

Bases have pH values of above 7 They taste bitter and chalky Bases turn litmus paper blue and methyl orange yellow A base which is water-soluble is referred to as an alkali They are metal hydroxides Bases are usually oxides or hydroxides of metals, except for ammonia Bases (alkalis) are proton acceptors as they ionize in solution producing OH– ions which can accept protons These OH– ions make the aqueous solution alkaline

Ma Va = Mb Vb M =molarity/concentration V= volume in cm3 a=acid b=base

Measure amount of unknown concentration solution and place in beaker Add indicator Titrate using known concentration until the endpoint is reached Calculate the concentration of the solution in the beaker

Titration Titration of acid and alkali to make salt and water The salt is a soluble salt so you have to crystallise it The Alkali is the solution Evaporation method Needs excess addition of insoluble base/metal with acid Need to filter then crystallise it Precipitation Mixing two solutions of soluble salt to make an insoluble salt Need to filter then wash/dry it

All K+, Na+, NH4+ = Soluble​ All Ethanoate, CH3COO- & Nitrate, NO3- = Soluble​ All Carbonate, CO32- = Insoluble, except K+, Na+, NH4+​ All Halides (Cl-,Br-,I-)= Soluble, except Ag+, Pb2+ All SO42- = Soluble, except Pb2+, Ba2+, Ca2+

• acid+alkali titration - acid+excess insoluble solid (reactive metal, base or carbonate)

This involves mixing solutions of two soluble salts that between them contain the ions that make up the insoluble salt. It is made by two methods • direct combination • precipitation

use sulfuric acid

use hydrochloric acid

Strong acids and bases ionize completely in water, producing solutions of very low pH for an acid or very high pH for a base

Weak acids and bases partially ionize in water and produce pH values which are closer to the middle of the pH scale

Strong acids include HCl and H2SO4 and strong bases include the Group I hydroxides

Weak acids include organic acids such as ethanoic acid, CH3COOH (aectic acid) and weak bases include aqueous ammonia

For both weak acids and bases, there is usually an equilibrium set-up between the molecules and their ions once they have been added to water Example of a weak acid: propanoic acid CH3CH2COOH ⇌ H+ + CH3CH2COO- Example for a weak base: aqueous ammonia NH3 + H2O ⇌ NH4+ + OH- In both cases the equilibrium lies to the left, indicating a high concentration of intact acid / base molecules, with a low concentration of ions in solution

Acids react with metals to form salt and hydrogen

Acids react with bases to form salt and water

Acids react with carbonates to form salt, water and carbon dioxide

Bases react with ammonium salts to form salt, water and ammonia

Universal indicator is a mixture of indicators. It is useful because it shows a range of colours from pH 1–14.​ pH meter Direct distinction between acid and base Litmus paper Direct distinction between acid and base Universal Indicator DIfferent shades for each pH

Stands for potential of hydrogen Formula is ㏒10(value of mol)

An oxide is a compound of oxygen and another element

acidic oxides basic oxides amphoteric oxides neutral oxides

Acidic oxides are oxides of non-metals (noble gases don’t form acidic oxides) Acidic oxides are often gases at room temperature Acidic oxides react with water to form acidic solutions E.g. sulfur trioxide + water -> sulfuric acid (so3+h20-> H2SO4) Acidic oxides react with bases and alkalis to produce salts and water E.g carbon dioxide + sodium hydroxide -> sodium carbonate + water (CO2+2NaOH -> Na2CO3 + H2O)