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# Chem 08 The Mole

### Chemical quantities terminology.

Question | Answer |
---|---|

relative mass of an atom on the "C-12 = 12.000000" scale | atomic mass |

sum of the masses of atoms in an ionic formula | formula mass |

sum of the masses of atoms in a molecule | molecular mass |

unit for measuring atomic, formula, or molecular masses; one-twelfth the mass of a C-12 isotope | atomic mass unit; a.m.u. OR u.; (aka 'dalton') |

atomic, formula, or molecular mass measured in grams | gram-atomic mass (g.a.m.), gram-formula mass (g.f.m.), gram-molecular mass (g.a.m.) |

amount of substance containing 6.022 x 10^23 representative particles | a mole |

mass of one mole of a substance | molar mass |

representative particles (building blocks) of most elements | atoms |

representative particles (building blocks) of covalent compounds and diatomic elements | molecules |

representative particles (building blocks) of ionic compounds | formula units |

honorary name given to 6.022 x 10^23, the # of representative particles in 1 mole | Avogadro's number |

obtained by finding out what portion of a compound is contributed by each element (and by water in the case of a hydrate) | percent composition |

the volume of a gas that contains Avogadro's number (6.022 x 10^23) of representative gaseous particles | molar volume |

average pressure exerted by the atmosphere at sea level | standard pressure (SP) a.k.a.: 1 atmosphere a.k.a. 14.7 psi, etc. |

standard temperature and pressure (S.T.P.) for gases | 273 K (0 oC) and 1 atm |

molar volume of a gas at STP | 22.4 liters |

simplest whole # ratio of atoms in the formula of a compound | empirical formula |

equal volumes of different gases at the same temperature and pressure contain equal numbers of gas particles | Avogadro's hypothesis |

If solving for empirical formula from % composition and find coefficient ratio of 1 to ?.33 or 1 to ?.67, which multiplier is applied to both? | 3x Ex: 3x(1 and 1.33) = 3 to 4 ratio Ex: 3x(1 and 1.67) = 3 to 5 ratio |

If solving for empirical formula from % composition and find coefficient ratio of 1 to 1.25, or 1 to 1.75, which multiplier is applied to both? | 4x 4x(1 and 1.25) = 4 to 5 ratio 4x(1 and 1.75) = 4 to 7 ratio |

If solving for empirical formula from % composition and find coefficient ratio of 1 to 1.5, which multiplier is applied to both? | 2x 2(1 and 1.5) = 2 to 3 ratio |

FINDING MOLECULAR FORMULA If empirical formula is C2H5, and... molecular weight is 58.0, then... Solve for "X" and give the molecular formula!!! | (mass C2H5)X = 58.0 29X=58 X=2 C4H10 |

total atoms in formula (NH4)2SO4 | 15 |

total atoms in formula Pb3(PO4)4 | 23 |

steps to find empirical formula from percent composition | 1. pretend you have 100 g of compound 2. change % to grams 3. change g to moles 4a. divide by smallest mole 4b. find multiplier if needed 5. use #'s as subscripts |

how to find molecular formula from empirical formula and molar mass | 1. (E.F. mass)X = molar mass 2. solve for X 3. use X to multiply all subscripts |

Created by:
goakley