H 1 Hydrogen 1.00794 | Periodic Table | He 2 Helium 4.002602 | |||||||||||||||

Li 3 Lithium 6.941 | Be 4 Beryllium 9.012182 | of the Elements | B 5 Boron 10.811 | C 6 Carbon 12.0107 | N 7 Nitrogen 14.0067 | O 8 Oxygen 15.9994 | F 9 Fluorine 18.9984032 | Ne 10 Neon 20.1797 | |||||||||

Na 11 Sodium 22.98976... | Mg 12 Magnesium 24.305 | mouse/touch for more information | Al 13 Aluminum 26.9815386 | Si 14 Silicon 28.0855 | P 15 Phosphorus 30.973762 | S 16 Sulfur 32.065 | Cl 17 Chlorine 35.453 | Ar 18 Argon 39.948 | |||||||||

K 19 Potassium 39.948 | Ca 20 Calcium 40.078 | Sc 21 Scandium 44.955912 | Ti 22 Titanium 47.867 | V 23 Vanadium 50.9415 | Cr 24 Chromium 51.9961 | Mn 25 Manganese 54.938045 | Fe 26 Iron 55.845 | Co 27 Cobalt 58.933195 | Ni 28 Nickel 58.6934 | Cu 29 Copper 63.546 | Zn 30 Zinc 65.38 | Ga 31 Gallium 69.723 | Ge 32 Germanium 72.63 | As 33 Arsenic 74.9216 | Se 34 Selenium 78.96 | Br 35 Bromine 79.904 | Kr 36 Krypton 83.798 |

Rb 37 Rubidium 85.4678 | Sr 38 Strontium 87.62 | Y 39 Yttrium 88.90585 | Zr 40 Zirconium 91.224 | Nb 41 Niobium 92.90628 | Mo 42 Molybdenum 95.96 | Tc 43 Technetium (98) | Ru 44 Ruthenium 101.07 | Rh 45 Rhodium 102.9055 | Pd 46 Palladium 106.42 | Ag 47 Silver 107.8682 | Cd 48 Cadmium 112.411 | In 49 Indium 114.818 | Sn 50 Tin 118.71 | Sb 51 Antimony 121.76 | Te 52 Tellurium 127.6 | I 53 Iodine 126.90447 | Xe 54 Xenon 131.293 |

Cs 55 Caesium 132.9054 | Ba 56 Barium 132.9054 | Hf 72 Hafnium 178.49 | Ta 73 Tantalum 180.94788 | W 74 Tungsten 183.84 | Re 75 Rhenium 186.207 | Os 76 Osmium 190.23 | Ir 77 Iridium 192.217 | Pt 78 Platinum 195.084 | Au 79 Gold 196.966569 | Hg 80 Mercury 200.59 | Ti 81 Thallium 204.3833 | Pb 82 Lead 207.2 | Bi 83 Bismuth 208.9804 | Po 84 Polonium (209) | At 85 Astatine (210) | Rn 86 Radon (222) | |

Fr 87 Francium (223) | Ra 88 Radium (226) | Rf 104 Rutherfordium (267) | Db 105 Dubnium (268) | Sg 106 Seaborgium (271) | Bh 107 Bohrium (272) | Hs 108 Hassium (270) | Mt 109 Meitnerium (276) | Ds 110 Darmstadium (281) | Rg 111 Roentgenium (280) | Cn 112 Copernicium (285) | Uut 113 Unutrium (284) | Uuq 114 Flerovium (289) | UuP 115 Ununpentium (288) | Lv 116 Livermorium (293) | Uus 117 Ununseptium (294) | Uuo 118 Ununoctium (294) | |

La 57 Lanthanum 138.90547 | Ce 58 Cerium 140.116 | Pr 59 Praseodymium 140.90765 | Nd 60 Neodymium 144.242 | Pm 61 Promethium (145) | Sm 62 Samarium 150.36 | Eu 63 Europium 151.964 | Gd 64 Gadolinium 157.25 | Tb 65 Terbium 158.92535 | Dy 66 Dysprosium 162.5 | Ho 67 Holmium 164.93032 | Er 68 Erbium 167.259 | Tm 69 Thulium 168.93421 | Yb 70 Ytterbium 173.054 | Lu 71 Lutetium 174.9668 | |||

Ac 89 Actinium (227) | Th 90 Thorium 232.03806 | Pa 91 Protactinium 231.0588 | U 92 Uranium 238.02891 | Np 93 Neptunium (237) | Pu 94 Plutonium (244) | Am 95 Americium (243) | Cm 96 Curium (247) | Bk 97 Berkelium (247) | Cf 98 Californium (251) | Es 99 Einstenium (252) | Fm 100 Fermium (257) | Md 101 Mendelevium (258) | No 102 Nobelium (259) | Lr 103 Lawrencium (262) |

Copper sulfate pentahydrate, expressed in chemical notation as CuSO4-5H2O, represents a “hydrate.” Hydrates consist of an ionic substance -- a compound comprised of a metal and one or more nonmetals -- plus water molecules, where the water molecules actually integrate themselves into the solid structure of the ionic compound. This means, however, that a 100-gram sample of copper sulfate pentahydrate does not consist of 100 grams of copper sulfate. Chemists compensate for this by expressing the mass of copper sulfate as a percentage of the sample’s total mass. In simplest terms, the concentration as percent mass represents the number of grams of copper sulfate in a 100-gram sample of copper sulfate pentahydrate.

Calculate the formula weight of copper sulfate pentahydrate, CuSO4-5H2O. Multiply the atomic weight of each atom, as found on the periodic table of the elements, by the number of atoms in the formula and then add together all of the results. Copper, for example, exhibits an atomic mass of 63.55 atomic mass units, or amu, and the formula contains one Cu atom. Therefore, Cu = 63.55 * 1 = 63.55 amu. The other atoms in the formula are S = 32.07 * 1 = 32.07 amu; O = 16.00 * 9 = 144.00 amu; and H = 1.01 * 10 = 10.10 amu. Combine these figures to get the formula weight: 63.55 + 32.07 + 144.00 + 10.10 = 249.72 amu.

Calculate the formula weight of the copper sulfate, CuSO4, without the water. In this case, Cu = 63.55 * 1 = 63.55 amu; S = 32.07 * 1 = 32.07 amu; and O = 16.00 * 4 = 64.00 amu. These values total 159.62 amu.

Determine the concentration by mass percent by dividing the formula weight of CuSO4 by the formula weight of CuSO4-5H2O and multiplying by 100 percent:

159.62 / 249.72 * 100 = 63.92 percent.

This means that a 100-gram sample of copper sulfate pentahydrate will contain 63.92 grams of copper sulfate. It also means that copper sulfate pentahydrate contains 100 - 63.92 = 36.08 percent water by mass.

#### Tip

Many chemistry students conduct an experiment in which they determine the percent water by mass in a sample of copper sulfate pentahydrate by heating the sample and measuring the mass lost during heating. See Resources for details.