than 7 and aqueous solutions of alkalis have pH values greater than 7. In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the equation: H+ (aq) + OH– (aq) H2O (l) 5.4.2.5 A strong acid is completely Use and explain the 1 Explain the meaning of the Use universal indicator or a (HT ionised in aqueous solution. terms dilute and following terms: pH probe to measure the pH only) Examples of strong acids are concentrated (in terms dilute of hydrochloric acid, hydrochloric, nitric and of amount of concentrated ethanoic acid, sodium sulfuric acids. substance), and weak weak hydroxide and ammonium and strong (in terms of strong. hydroxide. Be careful to use A weak acid is only partially the degree of ionisation) the same concentration of ionised in aqueous solution. in relation to acids. Explain why strong acids each. Examples of weak acids are are completely ionised in Measure the pH of different ethanoic, citric and carbonic Describe neutrality and aqueous solutions but a acids at different acids. relative acidity in terms weak acid is only partially concentrations. of the effect on ionised. For a given concentration of hydrogen ion Compare the rate of reaction aqueous solutions, the concentration and the Recall examples of strong when magnesium is dipped stronger an acid, the lower numerical value of pH and weak acids. in hydrochloric acid and the pH. (whole numbers only). ethanoic acid of the same concentration. WS 4.1
than 7 and aqueous solutions of alkalis have pH values greater than 7. In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the equation: H+ (aq) + OH– (aq) H2O (l) 5.4.2.5 (HT only) A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids. A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids. For a given concentration of aqueous solutions, the stronger an acid, the lower the pH. Use and explain the terms dilute and concentrated (in terms of amount of substance), and weak and strong (in terms of the degree of ionisation) in relation to acids. Describe neutrality and relative acidity in terms of the effect on hydrogen ion concentration and the numerical value of pH (whole numbers only). WS 4.1 1 Explain the meaning of the following terms: dilute concentrated weak strong. Explain why strong acids are completely ionised in aqueous solutions but a weak acid is only partially ionised. Recall examples of strong and weak acids. Use universal indicator or a pH probe to measure the pH of hydrochloric acid, ethanoic acid, sodium hydroxide and ammonium hydroxide. Be careful to use the same concentration of each. Measure the pH of different acids at different concentrations. Compare the rate of reaction when magnesium is dipped in hydrochloric acid and ethanoic acid of the same concentration.