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) |

To calculate the number of moles in a solution is to calculate how many molecules the solution contains. In order to do this, you need to know the volume of the solution and how much solute has been dissolved in it, as well as the molar mass of the solute.

## Understanding Moles

A mole is a huge number used to measure atoms. It is equal to the number of atoms in 12 grams of carbon-12, which is approximately 6.022 x 10^{23} atoms. Just as it's easier to measure intergalactic distances in light years rather than inches, it's easier to count atoms in moles than in billions or trillions.

One mole of any element or chemical compound is always the same number. One mole of hydrogen is the same as one mole of uranium or one mole of glucose. Their mass, however, is different.

## Calculating Molar Mass

Every element has a different molar mass, expressed as grams per mole. For example, one mole of sodium (Na) has a mass of 22.9898 g/mol. The molar mass of chlorine (Cl) is 35.4530 g/mol.

Since most molecules are made of more than one element, you often have to figure out the molar mass of a molecule by breaking it down into its elements. You can find the molar mass of each element on the periodic table of elements.

For example, if you want to calculate the molar mass of NaCl, or table salt, you add the mass of each element. Each molecule has one Na and one Cl atom. Therefore the mass of one mole of NaCl is the mass of Na plus the mass of Cl:

NaCl = Na + Cl

NaCl = 22.9898 g/L + 35.4530 g/L

NaCl = 58.4538 g/L

Note that the number of atoms in a molecule varies. Each molecule of H_{2}0, for example, has two hydrogen atoms and one oxygen atom.

## Calculating Molarity

Molarity is the number of moles per liter of solution, expressed as M. To calculate molarity, use the equation:

molarity = moles of solute / liters of solution

Before you can use this equation, you first need to know how many moles of solute are in the solution. To do this, multiply the mass of solute you have by its molar mass conversion factor. For example, if you have mixed 25g of table salt, or NaCl, into 2 liters of water, you first need to determine how many moles are in 25g of NaCl.

One mole of NaCl has a mass of approximately 58.5 grams. This gives it a conversion factor of 1/58.5.

Multiplying 25g by 1/58.5, which is the same as dividing 25 by 58.5, tells us that there are 0.427 moles of NaCl in the solution. Now you can use the equation and plug in the numbers:

molarity = moles of solute / liters of solution

molarity = 0.427/2

molarity = 0.2135

Because the molarity conversion factor used here is only accurate to three decimal places, round off the molarity. Therefore:

molarity = 0.214 M NaCl