The recommended daily allowance of the niacin (vitamin B3) is 16 mg per day for man. The molecular formula for niacin is C6H5NO2. Calculate the number of molecules of niacin in 16 mg.

High-density lipoprotein (HDL) cholesterol is the good cholesterol because adequate levels reduce the risk of heart disease and stroke. HDL levels between 40. and 59 mg/dL are typical for a healthy individual. What is this range of HDL cholesterol in units of mol/L? The formula for cholesterol is C27H46O.

Calculate the mass in grams of 3.839 moles of (a) hydrazine, a rocket propellant. (b) caffeine, C4H5N2O. (c) theobromine, C7H8N4O2, the alkaloid present in chocolate and cocoa.

3.96 Methyl cyanoacrylate is the chemical name for the substance sold as Super Glue, and it has the chemical formula C5H5NO2. Calculate the number of molecules of this substance in a 1.0-ounce tube of Super Glue, assuming that the glue is 80% methyl cyanoacrylate by mass.

Two general chemistry students working together in the lab weigh out 0.832 g of CaCl2 2 H2O into a crucible. After heating the sample for a short time and allowing the crucible to cool, the students determine that the sample has a mass of 0.739 g. They then do a quick calculation. On the basis of this calculation, what should they do next? (a) Congratulate themselves on a job well done. (b) Assume the bottle of CaCl2 2 H2O was mislabeled; it actually contained something different. (c) Heat the crucible again, and then reweigh it.

The compound 1-propanethiol, which is the eye irritant released when fresh onions are chopped up, has the chemical formula C3HyS and a formula mass of 76.18 amu. What number does y stand for in the chemical formula of the compound?

Express the composition of each of the following compounds as the mass percents of its elements. a. formaldehyde, CH2O b. glucose, C6H12O6 c. acetic acid, HC2H3O2

Atomic masses are relative masses. What does this mean?

Morphine, a narcotic substance obtained from opium, has the molecular formula C17H19NO3. What is the mass percentage of each element in morphine (to three significant figures)?

You have a pure sample of the antiseptic aminacrine, C13H10N2. Calculate the mass in grams of 0.06500 mol aminacrine. Calculate the number of aminacrine molecules in a 0.2480-g sample. Calculate the number of nitrogen atoms in this 0.2480-g sample. Calculate the mass of N in 100. g aminacrine.