As part of a soil analysis on a plot of land, a scientist wants to determine the ammonium content using gravimetric analysis with sodium tetraphenylborate, Na+B(C6H5)4−. Unfortunately, the amount of potassium, which also precipitates with sodium tetraphenylborate, is non‑negligible and must be accounted for in the analysis. Assume that all potassium in the soil is present as K2CO3 and all ammonium is present as NH4Cl. A 5.095 g soil sample was dissolved to give 0.500 L of solution. A 150.0 mL aliquot was acidified and excess sodium tetraphenylborate was added to precipitate both K+ and NH4+ ions completely. B(C6H5)4-+K+⟶KB(C6H5)4(s) B(C6H5)4-+NH4+⟶NH4B(C6H5)4(s) The resulting precipitate amounted to 0.269 g. A new 300.0 mL aliquot of the original solution was made alkaline and heated to remove all of the NH4+ as NH3. The resulting solution was then acidified, and excess sodium tetraphenylborate was added to give 0.129 g of precipitate. Find the mass percentages of NH4Cl and K2CO3 in the original solid.
As part of a soil analysis on a plot of land, a scientist wants to determine the ammonium content using gravimetric analysis with sodium tetraphenylborate, Na+B(C6H5)4−. Unfortunately, the amount of potassium, which also precipitates with sodium tetraphenylborate, is non‑negligible and must be accounted for in the analysis. Assume that all potassium in the soil is present as K2CO3 and all ammonium is present as NH4Cl.
A 5.095 g soil sample was dissolved to give 0.500 L of solution. A 150.0 mL aliquot was acidified and excess sodium tetraphenylborate was added to precipitate both K+ and NH4+ ions completely.
The resulting precipitate amounted to 0.269 g. A new 300.0 mL aliquot of the original solution was made alkaline and heated to remove all of the NH4+ as NH3. The resulting solution was then acidified, and excess sodium tetraphenylborate was added to give 0.129 g of precipitate.
Find the mass percentages of NH4Cl and K2CO3 in the original solid.
| Compound | Formula mass |
|---|---|
| KB(C6H5)4KB(C6H5)4 | 358.33 g/mol358.33 g/mol |
| NH4B(C6H5)4NH4B(C6H5)4 | 337.27 g/mol337.27 g/mol |
| K2CO3K2CO3 | 138.21 g/mol138.21 g/mol |
| NH4ClNH4Cl | 53.492 g/mol |
Formula Masses are
| Compound | Formula mass |
| KB(C6H5)4 | 358.33 g/mol |
| NH4B(C6H5)4 | 337.27 g/mol |
| K2CO3 | 138.21 g/mol |
| NH4Cl | 53.492 g/mol |
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