(a) Define Kw mathematically by completing the expression. Kw = (b) Two solutions, V and W, are described. • V is HCl(aq). • W is NaOH(aq). • The concentration of HCl in V is the same as the concentration of NaOH in W. • The pH values of V and W differ by exactly 11.00 at 298 K.

1. (a)Define Kw mathematically by completing the expression. Kw = ....................................................................................................................................................[1]
2. (b)(i)Calculate the concentration of HCl in V. concentration of HCl in V = ........................................ moldm⁻³[2]
3. (b)(ii)Equal volumes of the two solutions V and W are mixed, giving solution X. Name solution X and state its pH. solution X ..................................................... pH .....................................................[1]
4. (b)(iii)A 1 cm³ sample of 1.0 moldm⁻³ HNO3 is added to 100 cm³ of solution X, forming mixture Y. A 1 cm³ sample of 1.0 moldm⁻³ KOH is added to 100 cm³ of solution X, forming mixture Z. Estimate the pH of mixtures Y and Z. No calculations are required. mixture Y ..................................................... mixture Z .....................................................[1]
5. (c)(i)CH3CH2COOH, CH3CCl2COOH and H2SO4 are all acidic. Suggest the trend in the relative acid strength of these three compounds. Explain your answer. strongest acid ................................................................................................. weakest acid explanation ..................................................................................................................................................................... ..................................................................................................................................................................... .....................................................................................................................................................................[3]
6. (c)(ii)When concentrated H2SO4 is added to water a series of acid-base reactions occurs. There are three conjugate acid-base pairs that can be identified during this series of reactions. Write the formulae of these three conjugate acid-base pairs. conjugate acid 1 .............................................. conjugate base 1 .............................................. conjugate acid 2 .............................................. conjugate base 2 .............................................. conjugate acid 3 .............................................. conjugate base 3 ..............................................[2]
7. (d)(i)The partition coefficient, Kpc, of a substance, Q, between hexane and water is 7.84 at 298 K. Q is more soluble in hexane than it is in water. Define partition coefficient, Kpc.[1]
8. (d)(ii)5.00 g of Q is shaken with a mixture of 100.0 cm³ of water and 100.0 cm³ of hexane at 298 K and left until there is no further change in concentrations. Calculate the mass of Q dissolved in the water. mass of Q = .............................................. g[1]
9. (d)(iii)A sample of Q is shaken with a different mixture of water and hexane and left until there is no further change in concentrations. It is found that the mass of Q dissolved in each solvent is the same. Use the Kpc value to suggest possible values for the volume of water used and the volume of hexane used. volume of water = .............................................. cm³ volume of hexane = .............................................. cm³[1]
10. (d)(iv)Q is more soluble in hexane than it is in water. It is suggested that Q is one of KCl, CH3(CH2)4OH or HCOOH. Identify Q. Explain your answer.[1]