Acid base titration Lab Report Example | Topics and Well Written Essays - 1250 words

Acid base titration - Lab Report Example This is because in acidic, basic conditions phenolphthalein indicator usually indicates colorless and pink/purple colors respectively. Background theory Acid – base titration is one of the most essential Titrimetric analysis techniques commonly used in wet analysis to determine quantities or concentrations of the reacting reagents (Patnaik, 2010, p. 57). This is a neutralization reaction whereby its endpoint or neutrality point is marked by the change of phenolphthalein’s color from pink/purple to colorless. Colorless color in this experiment is an indication the reaction has reached its endpoint or undergone a complete neutralization route, hence basic condition is exhausted and instead acidity is increasing. Endpoint refers to a point where an indicator changes its color and assumes another thereby implying an acid has completely neutralized the available basic solution (Parsons, Forsythe, Edge & Bewick 793). At exact endpoint, the solution’s nature is neutral bearing a pH value of 7 similar to that of pure water. The addition of more acid solution reduces the solution’s pH from 7 towards 1, hence increasing its acidity nature compared to when it was a basic and a having a pH value more than 7. However, the color continues to remain the same but extent of acidity increases with addition of extra acid solution to the titrant, which in this experiment is a Standard 0.10 mol. /dm3 Sodium Hydroxide. Suppose there is a need to plot titration curves, then potentiometer is more accurate than either weak organic acid indicator or a weak organic base indicator (Patnaik, 2010). Since, it gives exact values compared to the latter two, which only relays the change of solution’s color (Patnaik, 2010.p. 61). An indicator is a weak organic acid or weak organic base having a formula of HY or HOY correspondingly, where Y represents a complex organic ion (Patnaik, 2010). During reaction, HOY or HY indicator usually dissociates as shown in the reversible equation below (Patnaik, 2010, p. 61). HY + H2O H3O+ + Y- Color -1 Color – 2. Reversibility in the above equation depends on the amount of either acid or basic solution added during neutralization process, which implies more base or acid shifts the process to the right (Patnaik, 2010). Hence, change of color from 1 to 2. The general equation involved in the neutralization process is, Acid + Base/Alkali Salt + water (Neutralization reaction equation) Essential components or agents for the above neutralization process to reach its completion state include hydronium ions, H3O+ (aq) from the acid and hydroxide ions, HO- (aq) from a base/alkali. However, these ions must be in aqueous form (in water) to facilitate their free movement besides ensuring intimate interactions when reacting. Respective equations for both Dilute Hydrochloric acid and Dilute Sulphuric Acid are, Ordinary equations (1) HCl(aq) + NaOH(aq) Â ® NaCl(aq) + H2O(l) H+(aq) + Cl-(aq) +Na+ + OH(aq) Â ® Na+ + Cl-(aq) + H2O(l) (2) H2SO4 (aq) + NaOH(aq) Â ® NaSO4(aq) + H2O(l) 2H+(aq) + SO4- (aq) + Na+(aq) + OH-(aq) Â ® Na-(aq) + SO4-(aq) + H2O(l) After eliminating spectator ions these equations reduce to, (1b) H+ (aq) + OH (aq) Â ® H2O (l) (2b) 2H+ (aq) + OH-(aq) Â ® H2O (l) Or (3) H3O+1 + OH- Â ® 2H2O (l) However, moles of H+ ions in each side of the equation should be equal for the reaction to proceed to the right or neutralization to occur (York, 175). Molarity concept Titration calculation in this experiment entails use of stoichiometric mole ratio of H+ and OH- ions (Parsons, Forsythe, Edge & Bewick). Moles’ ratio comparison in this experim