Post-Laboratory Questions (Use the spaces provided for the answers and additiona
ID: 712928 • Letter: P
Question
Post-Laboratory Questions (Use the spaces provided for the answers and additional paper if necessary.) 1. List possible manipulation errors that might con- tribute to the following errors in results: (2) Could you separate the components of a mixture of PbCl2 and Mg(OH)2 using only cold water? (1) recovering a significantly smaller amount of NaCI than was present in the original sample; Briefy explain your answer (2) recovering a significantly larger amount of Sio2 than was present in the original sample. (3) A mixture was known to contain two of the three compounds listed in the above table. After the mixture of Compounds A and B was extracted with hot water and filtered, Compound A was obtained by evaporating the filtrate to dryness. Both Compounds and filtered 2. Use the information in the table to answer the fol- lowing questions. e to answer the fol- A and B were insoluble in cold water. soluble in: cold waterwater Identify Compounds A and B. Briefly explain your hot answer. PbCl2 no yes Mg(OH)2 nono Na2SO4 yes yes (1) Describe how you could separate the com- ponents of a mixture of PbCl2 and Na2SO4 and recover the two substances.
Explanation / Answer
1.
(1) Using higher amount of water would dissolve more NaCl in solution and thus we would get lower mass of NaCl.
(2) If the initial mass of sample was incorrectly measured as lower mass than actual value, the final value for SiO2 by subtraction of final to initial mass would be greater than actual value. Also If the final mass was not tared before meaurement, the mass would be greater for SiO2.
2. Information in table
(1) PbCl2 is insoluble in cold water whereas, Na2SO4 is soluble in cold water. Thus PbCl2 precipitate is filtered out of solution in cold condition and the filtrate has only Na2SO4 in it.
(2) PbCl2 is soluble in hot water whereas, Mg(OH)2 is insoluble in hot water. Thus Mg(OH)2 is filtered out of solution in hot condition and the filtrate has only PbCl2 in it.
(3) Compound A : PbCl2
Compound B : Mg(OH)2