The human body contains 63% H, 25.5% O, 9.45% C, 1.35% N, 0.31% Ca and 0.22% P, plus trace elements present in smaller quantities. Are these mole or mass percents? How many grams of each element are present in a 5-kg baby? What is the mass of deuterium in the baby if deuterium naturally constitutes about 0.014% of all hydrogen atoms?

Atomic masses are relative masses. What does this mean?

3.123 Most periodic tables provide molar masses with four or five significant figures for the elements. How accurately would you have to measure the mass of a sample of roughly 100 g to make a calculation of the number of moles of the chemical to have its significant figures limited by the molar mass calculation rather than the mass measurement?

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.

3.95 Cumene is a hydrocarbon, meaning that it contains only carbon and hydrogen. If this compound is 89.94% C by mass and its molar mass is 120.2 g/mol, what is its molecular formula?

Vitamin A has a molar mass of 286.4 g/mol and a general molecular formula of CxHyE, where E is an unknown element. If vitamin A is 83.86% C and 10.56% H by mass, what is the molecular formula of vitamin A?

Calculate, to two decimal places, the formula mass of each of the following substances. Obtain the needed atomic masses from the inside front cover of the text. a. C20H30O (vitamin A) b. C14H9Cl5 (DDT, formerly used as an insecticide) c. C8H10N4O2 (caffeine, a central nervous system stimulant) d. Ca(NO3)2 (calcium nitrate, gives fireworks their red color)

Chlorine exists mainly as two isotopes, 37Cl and 33Cl. Which is more abundant? How do you know?

Chalky, white crystals in mineral collections are often labeled borax, which has the molecular formula Na2B4O7 10H2O, when actually they are partially dehydrated samples with the molecular formula Na2B4O7 5H2O, which is more stable under the storage conditions. Real crystals of borax are colorless and transparent. (a) Calculate the percent mass that the mineral has lost when it partially dehydrates. (b) Is the percent boron by mass the same in both compounds?