Psychology Essay

675 WordsMay 22, 20153 Pages
Acidity, Alkalinity and pH Introduction to Sport and Exercise Physiology SPOR10022 Dr Simon Cooper Simon.Cooper@ntu.ac.uk Acids • When added to water, Hydrogen ions (H+) ‘dissociate’ from an acid H+(aq) + Cl-(aq) e.g. HCl • Bronsted & Lowry definition: • Acidity is a measure of the number of H+ ions dissociated into the fluid 2 19 November 2012 Strength of Acids Strong Acids Weak Acids Some acids are very corrosive – they dissolve away metals, skin, cloth Other acids are not so corrosive e.g. HCl, H2SO4 CH3COOH: - 1.3% H+ & CH3COO- 98.7% CH3COOH HCl: - 95% H+ & Cl- 5% HCl 19 November 2012 e.g. ethanoic acid, citric acid 3 1 Alkalis • When added to water, alkalis dissociate to produce OH- ions Na+(aq) + OH-(aq) e.g. NaOH - O H • Bronsted & Lowry definition: • Alaklinity is a measure of the number of OH- ions dissociated into the fluid 4 19 November 2012 Strength of Alkalis Strong Alkalis Weak Alkalis High concentration of OHions Low concentration of OHions e.g. ammonia in water e.g. NaOH NH3 + H20 - 97% Na+ & OH- 3% NaOH NH4+ + OH- - 1.3% as NH4+ & OH- 98.7% as NH3 5 19 November 2012 pH • Strength of an acid or alkali (liquid or in solution) is denoted using a scale of numbers called the pH scale • Ranges from 0 – 14 (neutral pH = 7, e.g. H2O) An acidic solution has a pH < 7 The more H+ ions are in the solution, the lower the pH An alkali solution has a pH of > 7 The more OH- ions are in the solution, the higher the pH 19 November 2012 6 2 7 19 November 2012 Calculating pH • Function of the H+ ion concentration • Need to know how many moles of H+ per litre • Remember: 1 mole = 6 x 1023 H+ ions pH = - log [H+] Concentration = 0.0000001 moles H+ per litre = 1 x 10-7 pH = 7 Concentration = 0.0001 moles H+ per

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