In this experiment you will titrate a solution of the hydroxide of a Group 1 element, Z, with sulfuric acid. The equation for the reaction is shown. Z may or may not be the same as X. 2ZOH(aq) + H2SO4(aq) → Z2SO4(aq) + 2H2O(l) FA 2 is 26.3 gdm-³ aqueous hydroxide of metal Z, ZOH. FA 3 is 0.0500 mol dm-³ sulfuric acid, H2SO4. bromophenol blue indicator

1. (a)Method • Pipette 25.0 cm³ of FA 2 into the 250 cm³ volumetric flask. • Add distilled water to the flask to make 250 cm³ of solution. Shake the flask thoroughly to ensure complete mixing. Label this solution FA 4. • Rinse the pipette with a little distilled water and then a little FA 4. • Fill the burette with FA 3. • Pipette 25.0 cm³ of FA 4 into a conical flask. • Add a few drops of bromophenol blue indicator. • Carry out a rough titration and record your burette readings in the space below. The rough titre is cm³. • Carry out as many accurate titrations as you think necessary to obtain consistent results. • Make sure your recorded results show the accuracy of your practical work. • Record in a suitable form in the space below all of your burette readings and the volume of FA 3 added in each accurate titration. I II III IV V VI VII[7]
2. (b)From your accurate titration results, calculate a suitable mean value to use in your calculations. Show clearly how you obtained this value. 25.0 cm³ of FA 4 required cm³ of FA 3.[1]
3. (c)(i)Calculations Give your answers to (c)(ii), (c)(iii) and (c)(iv) to the appropriate number of significant figures.[1]
4. (c)(ii)Calculate the number of moles of sulfuric acid present in the volume of FA 3 you calculated in (b). moles of H2SO4 =[1]
5. (c)(iii)Use your answer to (c)(ii) and the information on page 4 to calculate the concentration, in mol dm⁻³, of ZOH present in FA 4. concentration of FA 4 =[1]
6. (c)(iv)Calculate the concentration, in mol dm⁻³, of ZOH in FA 2. concentration of FA 2 =[1]
7. (c)(v)Use your answer to (c)(iv) and the information on page 4 to calculate the relative atomic mass, A₁, of Z. Hence identify Z. Show your working. Z is[2]
8. (d)Using the value for the relative atomic mass of Z that you calculated in (c)(v), calculate the percentage difference of your value from that shown in the Periodic Table. (If you did not obtain a value for the A, of Z, assume it is 32.0. Note, this is not the correct value.) percentage difference =[1]