# Hydrated Compound in a Mixture

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Indirect Gravimetric Determination of a Hydrated Compound in a Mixture Morgan Dufer I. The purpose of this lab was to find the percent of BaCl2*2H2O in a sample of unknown composition by using gravimetric analysis. II. Pre-lab Questions 1. What mass of MgCO3 is contained in a 2.750g solid sample consisting of only MgCO3 and MgO if heating to decompose all the MgCO3 according to the following equation leaves a solid residue weighing 2.160g? Magnesium oxide is unaffected by the heat. MgCO3(s) MgO (s) + Co2 (g) 2. a) Consider the reaction of question 2. Suppose a 3.250 g sample containing only MgCO3 and MgO is 42.6% MgO. How many grams of CO2 would be liberated by complete thermal decomposition of the MgCO3 in the sample? b) How much would the residue weigh? 3. Describe the location of the hottest portion of a burner flame. The tip of the inner blue flame is the hottest portion. 4. How will you know in this experiment when the hydrate BaCl2*2H20 has been completely dehydrated? It will be completely dehydrated when the difference in successive weights of the crucible, cover, and residue (after cooled to room temp.) is 0.0020 g or less. III. Data Mass of crucible, cover, and unknown sample | 29.082 g | Mass of crucible and cover | 23.110 g | 1st Mass of crucible, cover, and residue | 28.403 g | 2nd Mass of crucible, cover, and residue | 28.365 g | Mass of unknown sample used | 5.972 g | Mass of water lost by the sample | .717 g | Calculated mass of BaCl2* 2H2o in unknown sample | 4.86 g | % by weight of BaCl2*2H2O in unknown sample | 81.4 % | % by weight of NaCl in unknown sample | 18.6 % | IV. Calculations V. Post-lab