fill in the blanks please! t 8 Section Date Table 8.1 Mass data for analysis of

Question

fill in the blanks please!

t 8 Section Date Table 8.1 Mass data for analysis of alum. Mass of weighing paper for alum (g) Mass of weighing paper plus alum sample (g) Mass of empty heated and cooled crucible (g) Mass of crucible plus Baso, after first heating (g) 31.2306 Mass of crucible plus Baso, after second heating (g) 3 23 ia Mass of crucible plus Baso, after third heating (g) Instructor's initials CALCULATIONS Table 8.2. Percent SO in alum. Mass of alum (g) Mass of BaSO4 (g) Percent So in your alum sample Theoretical percent so in your pure alum sample Analytical purity of your alum sample

Explanation / Answer

Mass of weighing paper for alum = 0.40125 g

Mass of weighing paper + alum = 1.43179 g

Mass of empty heated & cooled crucible = 29.8406 g

Mass of empty heated & cooled crucible +BaSO4 after first heating = 31.2316 g

Mass of empty heated & cooled crucible +BaSO4 after second heating = 31.2319 g

Find the calculation for -

1-Mass of alum = mass of weighing paper plus alum sample - mass of weighing paper for alum

Mass of alum = 1.43179 – 0.40125

Mass of alum = 1.03054 g

2- Mass of BaS04 =

Mass of crucible plus BaSO4 after second heating - Mass of empty heated & cooled crucible

31.2319 g - 29.8406 g = 1.3913 g

3- Percent SO4^2- in alum sample-

Molar mass of BaSO4 = 233.4 g/mol

Moles of BaSO4 = 1.03054 g BaSO4 / 233.4 g/mol = 0.0044 mol BaSO4

Molar mass of SO42- = 96.07 g/mol

Weight of SO4 = 0.0044 mol SO4 * 96.07 g/mol = 0. 4227 g

% of SO4 0.4227 g / 1.03054 g x 100 = 41.01% Sulfate

4. Calculate the theoretical percent sulfate in this alum.

Sulfate: 96.07 g/mol

Alum: 474.2 g/mol

2 mol Sulfate / 1 mol Alum =

% Sulfate (2x 96.07 g)/mol/474.2 g/mol x100 = 40.5 %  

Experimental value (41.01% Sulfate) is very close to theoretical value (40.5% Sulfate), no reason for concern. It conclude that alum is fairly pure because the sulfate test was very close to their respective predicted value

KAl(SO4)2*2H2O(aq) + 2 BaCl2(aq) --> 2 BaSO4(s) + KCl(aq) + AlCl3(aq) + 12 H2O(l)

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