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# Chem 1 - Amount

### Amount of a Substance

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

Relative Atomic Mass | The weighted Average of a mass of an atom of an element, taking into account its naturally occurring isotopes, relative to 1/12th the mass of Carbon-12. |

Relative Atomic Mass Formula = | Ar = (Average mass of an atom of an element) / (1/12 of mass of atom of Carbon-12) |

Relative Molecular Mass | The relative molecular mass of a molecule is the mass of that molecule relative the mass of an atom of Carbon-12. Add the Ar of the Atoms in the molecule. |

Relative Molecular Mass Formula = | Mr = (Average Mass of a Molecule) / (1/12th mass of an atom of Carbon-12). |

Avagardo Constant: | The Number of molecules in 12 grams of Carbon-12. 6.022 x10^3 |

Number of Moles = | Mass of what you have / Mass of 1 mole (Mr). |

Pressure = | Force / Area |

Describe the effects on pressure for the following variables: Temp, Volume, Number of Moles: | Temp: increasing temp increases pressure, the inverse is true. Volume: Increasing Volume decreases pressure, inverse also true. No of Moles, Increasing the no of moles increases pressure, inverse true. |

Ideal Gas Constant: | PV=nRT (Pressure x Vol = No of Moles x Constant x Temp). |

Units of the Ideal Gas Constant | Vol = M^3, Temp = Kelvin (K), Pressure = Pa, R = J K-1 Mol-1. |

Empirical Formula: | A formula showing the simplest whole number ratio of atoms of each element in a compound. |

Molecular Formula: | A formula showing the actual number of each atom in a compound. |

What method is used to find Empirical Formula? | Combustion Analysis. Compound is burnt in Oxygen and then the products by mass are analysed. |

How to Calculate Empirical Formula: | Workout Number of moles of each element, divide all numbers by lowest amount, find ratio. |

Moles in a Solution: | (Concentration (M) x Volume (V)) / 1000 |

Concentration = | Number of moles / Volume |

When can we use the ideal gas equation? | To calculate the amount of gas produced in a Reaction |

How can we find concentration, experimentally? | Using a Titration. So long as we know the concentration of the acid and equation between them. |

Write a common Ionic equation: | H+ + OH- ---> H20 |

Titration explain the steps: | Fill burette with Acid (known concentration), measure out Alkali with Pipette and add to Flask with indicator, slowly add in acid until neutral, repeat until 2 results are the same. |

Atom Economy (percentage): | (Mass of desired produce / Amount of reactants) x 100 |

Reaction Yield (%): | (Mass (or moles) of desired product / theoretical maximum amount of desired product) x 100 |