Introduction to Topic 8 and Topic 18

You should be able to recall the characteristic properties of acids and bases and you should have plenty of practice at writing equations for the reactions of acids with hydroxides, oxides, carbonates, hydrogencarbonates and other bases such as ammonia as well as reactive metals. (If you do Option D : Medicinal chemistry this is very useful for D.4 on pH regulation of the stomach.) The distinction between strong and weak acids is covered and this emphasises the importance of language as you should be able to distinguish between the words “strong”, “concentrated” and “corrosive” when applied to an acid. The concept of the pH scale is included and at both Standard and Higher Level calculations involving the formula pH = − log₁₀[H⁺(aq)] are required. At both levels you also need to understand the use of indicators and pH meters in titrations. At Higher Level more types of calculations are required including the manipulation of logarithms for pH, pOH, K_a, K_b, pK_a and pK_b calculations (but not buffer calculations as these now only appear at Higher Level in Option B : Biochemistry under Proteins and Enzymes and at both Higher and Standard Level in Option D : Medicinal chemistry which specifically mentions the Henderson–Hasselbalch equation in the core topic B.4 on pH regulation of the stomach). As with equilibrium calculations, you are not expected to solve quadratic equations but use approximations instead. All students need to know and be able to apply the BrØnsted-Lowry theory of acids and bases and be able to link an acid with its conjugate base. However Lewis theory is only introduced at Higher Level and extended to cover 'curly arrows' in organic reaction mechanisms . At both levels the sub-topic 8.5 deals with acid deposition. This is effectively 'utilization' but, as it is clearly a sub-topic in its own right, it is assessable.