A 1.000-gram sample of NaOH (39.997 g/mol) which has been exposed to the air for some time (NaOH will adsorb water and CO2 from the ambient air) is dissolved in water and then diluted to 500.00 mL, 100.0 mL of this solution required 38.60 mL of 0.01062 M HCl to be titrated to a methyl orange endpoint (~pH 3). A second 100.00 mL portion is treated with excess BaCl2 and then diluted to 250 mL and filtered. 200 mL of the filtrate required 29.62 mL of HCl to titrate to phenolphthalein (~pH 8-9) endpoint. Calculate in the original sample: a.) the percentage of NaOH b.) the percentage of Na2CO3 (105.9898 g/mol) Make sure you use at least four significant figures for this calculation. Note that the adsorbed CO2 is converted to Na2CO3. The Ksp for BaCO3 (s) is 2.58 x 10-9 (extremely insoluble).
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A 1.000-gram sample of NaOH (39.997 g/mol) which has been exposed to the air for some time (NaOH will adsorb water and CO2 from the ambient air) is dissolved in water and then diluted to 500.00 mL, 100.0 mL of this solution required 38.60 mL of 0.01062 M HCl to be titrated to a methyl orange endpoint (~pH 3). A second 100.00 mL portion is treated with excess BaCl2 and then diluted to 250 mL and filtered. 200 mL of the filtrate required 29.62 mL of HCl to titrate to phenolphthalein (~pH 8-9) endpoint. Calculate in the original sample:
a.) the percentage of NaOH
b.) the percentage of Na2CO3 (105.9898 g/mol)
Make sure you use at least four significant figures for this calculation. Note that the adsorbed CO2 is converted to Na2CO3. The Ksp for BaCO3 (s) is 2.58 x 10-9 (extremely insoluble).
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