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# MCAT Equations

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

What is the Atomic number? | (Z) the number of protons |

What is the Mass number? | (A) the number of protons plus neutrons |

What is the Atomic mass unit? | 1.66* 10^23 |

What is the equation for energy (E)? | E = hf (h=Planck's constant) (f=frequency) |

What is Planck's constant? | 6.626 * 10 ^ -34 J*s |

What is the equation for the angular momentum of an electron? | L=nh / 2pi (n=quantum number) |

What is the equation for the energy of an electron? | E= -Rh / N^2 (Rh = Rydberg constant=2.18 *10^-18 J/electron) |

What is Rydbergs constant? | 2.18*10^-18 J/electron |

What is the equation for electromagnetic energy? | E=hc / (wavelength) c=speed of light in vacuum(3*10^8 m/s) =wavelength of the radiation |

What is the equation for the energy of an emitted photon? | E=hc = -Rh [(1/n^2initial) - (1/n^2final) |

What is the Heisenberg uncertainty principle? | It is impossible to simultaneously determine momentum and position of an electron |

What is the principle Quantum number? | (n) is the energy level and radius of an electrons orbilal |

What is the Azmuthal Quantum number? | (l) is the shape and number of subshells l=0-(n-1) 0=s 1=p 2=d 3=f |

What is the Magnetic Quantum number? | (m1) is the orbital within a subunit where an electron is likely to be found at a given moment in time m1= -l -> +l cant be l |

What is the spin quantum number? | (ms) is the spin orientation; can be -1/2 or +1/2 |

What is the atomic radius? | 1/2 the distance between the centers of two atoms of that element touching each other |

What is ionization energy | (IE) energy required to remove an electron from a gaseous atom or ion |

What is electronegativity? | the attractive force taht an atom will exert on an electron in a chemical bond. it is the attraction for bonding electrons |

What is the equation for formal charge? | V-N nonbonding - 1/2 N bonding |

How many bonds are in a trigonal planar arrangement? | 3 |

How many bonds are in a tetrahedral arrangement? | 4 |

How many bonds are in a trigonal bipyrimidal arrangement? | 5 |

How many bonds are in a octahedral arrangement? | 6 |

What are dispersion forces/London forces? | They are short lived and rapidly shifting dipoles |

What are dipole-dipole interactions? | they occur when the positive region of one molecule is close to the negative region of another molecule |

What is the molecular weight? | It is the sum of atomic weights of all of the atoms in a molecule |

What is the formula weight? | It is the addition of atomic weights of constituent ions according to its empirical formula |

What is Avagadros number? | 6.022*10^23 |

What is the equation for gram equivalent weight? | molar mass / n (protons, hydroxide ions, electrons, monovalent ions) |

What is the equation for equivalents? | mass of compound (g) / gram equivalent weight (g) |

What is the equation for molarity? | normality / n |

What is normality? | The measure of concentration = equivalents / liter |

What is the empirical formula? | It is the simplest whole number ratio of elements in a compound |

What is a molecular formula? | It is the exact number of atoms of each element in the compound |

What is the equation for percent composition? | (mass of X in formula / formula weight of compound) * 100 |

What is the equation for percent yield? | (actual yield / theoretical yield) * 100 |