The concentration of iron in a vitamin tablet was determined using absorbance spectroscopy. A vitamin tablet was dissolved in 10 mL of 6 M HCl. The resulting solution was transferred to a 100.0 mL volumetric flask and diluted to volume with DI water. A 1.00 mL aliquot of the vitamin stock solution was transferred to each of 5 100.0-mL volumetric flasks. To each flask, 10 ml each of 2 g/L hydroquinone and 1 g/L o-phenanthroline are added, along with varying volumes of a 40.5 mg/L Fe3 stock solution. Each solution was diluted to volume and allowed to react for 10 minutes. The absorbance of the resulting solutions was measured at 515 nm. Required:
Determine the mg of iron in the vitamin tablet.

Joseph has hypothesized that sound travels in waves. if he were following the scientific method, what should he do next? a. ask a question. b. test the hypothesis. c. study the results. d. tell other scientists about his hypothesis.

Astudent is given a sample of a blue copper sulfate hydrate. he weighs the sample in a dry covered porcelain crucible and got a mass of 23.875 g for the crucible, lid, and sample. the mass of the empty crucible and lid was found earlier to be 22.652 g. he then heats the crucible to expel the water of hydration, keeping the crucible at red heat for 10 minutes with the lid slightly ajar. on colling, he finds the mass of crucible, lid, and contents to be 23.403 g. the sample was changed in the process to very light clue anhydrous cuso4. if there are again 100.0 g of hydrate, how many grams of cuso4 are in it? how many moles of cuso4? (hint: molar mass of cuso4 = 159.6 g / mole. what per cent of the hydrate is cuso4? you may convert the mass of cuso4 to moles.)

How many moles of gas are present if p=11 atm, v=12l, t=185k?