As level Chem A Sample question paper H032/02 depth

As level Chem A Sample question paper H032/02 depth A student carries out an experiment to identify an unknown carbonate. the sample of carbonate is dissolved in apox. 100cm3 of distilled water in a beaker and the solution is transferred to a volumetric flask. the volume of solution is made up to 250cm3 with distilled water. suggested were the possible errors - A small amount of solid remained in weighing bottle - A small amount of solution remained in the beaker is the students statement correct? how could the procedure be improved? (2) - correct answersAre they correct? - Not about the solid remaining in the weighing bottle as its weighed by difference - Yes about the solution remaining in the beaker improvements: - RINSE out the beaker with distilled water, transfer it into the VM flask BEFORE making up the 250cm3 solution. Bromine disproportionates reacting with KOH solution - correct answersBr2 + 2KOH —> KBr + KBrO + H2O Calculate the enthalpy of FORMATION for IBr - correct answersAdd avg bond enthalpies of the reactants minus the avg B.E of the products Draw the dot and cross diagram of PBr3 stating it's shape and why. (3) - correct answersName - Pyramidal Explanation - 3 bonded pairs and 1 lone pair. Electron pairs repel as far as possible, taking a tetrahedral shape (making it pyramidal overall) Effect of increasing pressure on the RATE OF REACTION - correct answersIncreases rate of reaction as more molecules are closer together, so more collisions per unit time. Evidence for the isomer - correct answersIR between 1640 and 1750 for C=O Mass spec. peak at m/z = 29 showing its CHO+ and m/z = 15 (CH3) so its Ethanal How do we test for ammonium sulfate, (NH4)2SO4 ? - correct answersTo test for SULFATES, warm the mixture with NaOH (aq) then use a MOIST indicator paper to test