Amidosulfonic acid is a monoprotic acid with the formula HSOxNH2. In this experiment you will determine the value of x in the formula by titration with an alkali. FB 1 is amidosulfonic acid, HSOxNH2. You are supplied with approximately 3.0 g. FB 2 is 0.110 mol dm⁻³ sodium hydroxide, NaOH. thymolphthalein indicator

1. (a)Method Preparing a solution of amidosulfonic acid Weigh the empty beaker. Record the mass. Add 2.50–2.70 g of FB 1 to the beaker. Weigh the beaker and its contents. Record the mass. Calculate and record the mass of FB 1 used. Add approximately 100 cm³ of distilled water to the beaker and stir to dissolve FB 1. Transfer the solution to the 250 cm³ volumetric flask. Rinse the beaker twice with approximately 20 cm³ of distilled water each time and add to the volumetric flask. Add distilled water to the volumetric flask to make 250 cm³ of solution. Shake the volumetric flask to mix the solution thoroughly and label it FB 3. Titration of FB 3 Fill the burette with FB 2. Pipette 25.0 cm³ of FB 3 into a conical flask. Add a few drops of thymolphthalein to the conical flask. Carry out a rough titration. Record your burette readings and the rough titre 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 any recorded results show the precision of your practical work. Record all of your burette readings and the volume of FB 2 added in each accurate titration. I II III IV V VI VII VIII[8]
2. (b)From your accurate titration results, obtain a suitable value for the volume of FB 2 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm³ of FB 3 required .................................. cm³ of FB 2.[1]
3. (c)(i)Give your answers to (ii), (iii), (iv) and (v) to the appropriate number of significant figures.[1]
4. (c)(ii)Calculate the number of moles of sodium hydroxide, NaOH, in the volume of FB 2 calculated in (b). moles of NaOH = .................................. mol[1]
5. (c)(iii)One mole of sodium hydroxide neutralises one mole of amidosulfonic acid. Complete the equation for the reaction of amidosulfonic acid with sodium hydroxide. Include state symbols. ......NaOH...... + ......HSOxNH2...... → .................................. + .................................. State the number of moles of amidosulfonic acid that reacted with the number of moles of NaOH calculated in (ii). moles of HSOxNH2 = .................................. mol[1]
6. (c)(iv)Use your results on page 2 and your answer to (iii) to calculate the relative formula mass, Mr, of amidosulfonic acid. Mr of amidosulfonic acid = ..................................[1]
7. (c)(v)Calculate the value of x in the formula of amidosulfonic acid, HSOxNH2. x = ..................................[1]
8. (d)The salts produced from amidosulfonic acid are called amidosulfonates. You are to carry out an experiment using FB 1 to find out if barium amidosulfonate is soluble in water. Describe your experiment. Record your observation(s) and conclusion.[2]