Why is calcium oxalate converted to CaCO3 during gravimetry
Because CaCO3 is insoluble and can be filtered, collected, dried, and weighed.
During gravimetry, calcium oxalate is often converted to calcium carbonate (CaCO3) because calcium carbonate is more stable and less soluble than calcium oxalate. This conversion allows for the accurate determination of calcium content in a sample.
To understand why this conversion is necessary, let's first explain what gravimetry is. Gravimetry is a quantitative analytical method that involves the measurement of the weight of a solid substance to determine the amount of a specific chemical compound in a sample. In the case of calcium analysis, gravimetry is used to determine the calcium content by isolating it as a solid precipitate.
Calcium oxalate is a common compound that forms when calcium ions (Ca2+) react with oxalate ions (C2O42-) in a sample. However, calcium oxalate is not an ideal compound for gravimetric analysis because it is relatively soluble in water. Its solubility makes it difficult to separate and weigh accurately.
Calcium carbonate, on the other hand, is less soluble and more stable than calcium oxalate. It can be obtained by reacting calcium oxalate with a solution of calcium chloride (CaCl2). The reaction produces calcium carbonate as a precipitate, which can be collected, filtered, dried, and weighed accurately.
The conversion of calcium oxalate to calcium carbonate allows for a more precise gravimetric analysis of calcium content in a sample because the calcium carbonate precipitate is easier to handle and has a lower solubility, making it less likely to dissolve and affect the accuracy of the measurement.
In summary, the conversion of calcium oxalate to calcium carbonate during gravimetry is necessary to obtain a more stable and less soluble compound that can be accurately weighed, ensuring reliable results in the determination of calcium content in a sample.