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Data from synthesis: mass of aluminum metal (g) mass of alum watch (g) (09.13 g

ID: 959523 • Letter: D

Question

Data from synthesis: mass of aluminum metal (g) mass of alum watch (g) (09.13 g lo l q 57. mass of watch glass (g) total mass of alum (g) 12 12 9 Questions and Calculations: 1. Balance the equation for the preparation of alum. This balanced equation has somewhat unusual coefficients.) 22 Hoa Al (s) KOH (aq) H2SO4 (aq) H2 (g) KAI(SO) 12H20 (s) In the formula [KAl(so) 12H20], are 12 water molecules has It is also possible to prepare the anhydrous compound potassium aluminum sulfate, which the formula KAI (SO4)2 2a. On the molecular scale, describe how a crystal of alum differs from a crystal of potassium aluminum sulfate. On the molecular scale they are the san 2b. When performing stoichiometric calculations with alum, what do you need to do differently to calculate the number of moles of alum as compared to potassium aluminum sulfate? July 2& 2015 page 3A-3 Chem 201 Alum Synthesis Report Sheet

Explanation / Answer

2a ) Alum is a hydrated potassiun aluminium sulphate having molecular formula KAl ( SO4)2 . 12 H2O. And potassium aluminium sulphate is the molecular formula KAl ( SO4)2. Only difference is the presence of water molecule in alum.

2b) During stoichiometric calculations , the molecular wt of alum is taken with 12 water molecules ie 474 g/mol.

and mol wt of potassium aluminium sulphateis taken without water molecules ie 258.2 g/mol.