Hi, I have a question that I do not understand, the teacher did not even explain this kind of problem and could not find it in my book either. Please help
A sample of impure sodium carbonate decahydrate weighed 3.841g. The sample was dissolved in water and excess hydrochloric acid was added. The carbon dioxide gas that was evolved was collected over water on a day when the atmospheric pressure was 746.2mm Hg and the temperature was 20.6C. Then volume of carbon dioxide collected was 288.3mL. Given that the vapour pressure of water at 20.6C is 18.1 mm Hg, find the percentage purity of the sodium carbonate decahydrate.
Na2CO3.10H2O(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + 12H2O(l)
A sample of impure sodium carbonate decahydrate weighed 3.841g. The sample was dissolved in water and excess hydrochloric acid was added. The carbon dioxide gas that was evolved was collected over water on a day when the atmospheric pressure was 746.2mm Hg and the temperature was 20.6C. Then volume of carbon dioxide collected was 288.3mL. Given that the vapour pressure of water at 20.6C is 18.1 mm Hg, find the percentage purity of the sodium carbonate decahydrate.
Na2CO3.10H2O(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + 12H2O(l)
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You need to calculate the actual moles of CO2 collected. You need to subtract the vapor pressure of water from the total pressure. Then put this intoPV=nRT along with the volume collected and temp. (remember to change to K). Once you solve for the moles of CO2, use stoich. to calculate the moles of the s.c. decahydrate reacted. Convert that to grams and then divide by 3.481g for the percent purity.