Composition of a Mixture.docx - Composition of a Mixture...

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Composition of a Mixture Objective: To determine the percentage of NaHCO 3 in an unknown mixture of NaCl and NaCO 3 , by determining the weight loss of CO 2 and H 2 O when the mixture is heated on a hot place. Pre-Lab Questions: Pre-lab questions were attached on the first page. Introduction: If bicarbonate is heated in a crucible open to the air, the gaseous products, CO 2 and H 2 O, will escape into the air; and sodium carbonate (Na 2 CO 3 ) will be the only product remains in the beaker. The reaction is: 2NaHCO 3 (s) Na 2 CO 3 + CO 2 (g) + H 2 O(g) According to the balanced equation, 1 mole of Na 2 CO 3 (105.98 × 1 = 105.98 g) is produced from 2 moles of NaHCO 3 (84.00 × 2 = 168.00 g). When the reaction is complete, the weight of loss is equal to 168.00 − 105.98 = 62.02 g. This means if 168.00 g NaHCO 3 is decomposed, there will be 62.02 g H 2 O and CO 2 lost in the reaction. Chlorides of the same metal are not easily decomposed if the temperature below 750 . That means when NaCl is heated, it will not decomposed and there will be no weight change in the reaction. This means if a mixture contains both NaCl and NaHCO 3 is heated over the hot plate, only NaHCO 3 is decomposed: NaCl(s) + 2NaHCO 3 (S) Na 2 CO 3 (S) + H 2 O(g) + CO 2 (g) + NaCl(s)
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After heating, there is no weight change of NaCl. H
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