Calcium in flour was analyzed by the following procedure. First, 0.1450 g of flo
ID: 798551 • Letter: C
Question
Calcium in flour was analyzed by the following procedure. First, 0.1450 g of flour were digested in 10 mL of boiling concentrated nitric acid for 30 minutes before adding 5 mL of concentrated perchloric acid and boiling for another 30 minutes. The resulting solution was transferred to a 100.0 mL volumetric flask and diluted to the line with deionized water. From this, 20.00 mL were pipetted into each of four separate 50-mL volumetric flasks. To these were added 0, 5.00, 10.00 and 15.00 mL of 7.94 mg/L calcium standard solution before diluting to the line with deionized water. Atomic absorption of calcium was measured for all four of the resulting solutions, giving the data shown below. A blank measurement gave an absorption of zero.
Description of solution Atomic absorption Unspiked solution (50.00 mL) 0.127 Spiked with 5.00 mL 7.94 mg/L Ca 0.242 Spiked with 10.00 mL 7.94 mg/L Ca 0.357 Spiked with 15.00 mL 7.94 mg/L Ca 0.472Explanation / Answer
1. 7.218
2. 8.12
3. 0.12