• Revision:General equations and definitions

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > General Equations and Definitions

• Atomic Masses = the number of protons and neutrons
• Atomic Number = number of protons and therefore also the number electrons
• Electron Shielding = This is where electrons in the inner shells of a atom stop the full charge of the nucleus effect electrons outside that shell, e.g. if a shell has 6 electrons it will reduce the effective nuclear charge by 6+.
• Enthalpy = This is the energy change of a substance per mole.
 Particles in the atom Charge in Coulombs Mass in Kg Relative Charge Relative mass P proton 1.602 x 10–9 1.672 x 10-27 +1 1 N neutron 0 1.675 x 10-27 0 1 E electron 1.602 x 10–9 9.109 x 10-31 -1 1/1836

• Energy Transfer = Mass ´ Specific heat capacity ´Temperature change
• Energy Transferred = M x C x DT
• For enthalpy divide by the number of moles.

• Concentration = moles / volume
• Working out formula by percentage using RAM, divide the percentage by the RAM, E.g. for 22.02% of Carbon(12), 4.59% of hydrogen(1), 73.39% of Bromide(80): we get:
• 22.02 / 12 = ~ 2; 4.59 / 1= ~ 5; 73.39 / 80 = ~ 1 \ C2 H5 Br

• At 20°C; 1 mole of gas will occupy 24 dm3, this is the R.T.P.
• At 0°C; 1 mole of gas will occupy 22.414 dm3, this is the S.T.P.

• Moles = Mass / RAM

 Radio Active Decay Basically what happens Example (alpha ) decay The release of a helium nucleus(2 P and 2N) from the nucleus (beta) decay A neutron decomposes to create aelectron and proton, the electron isthen expelled from the nucleus Gamma Decay The nucleus has too much energy,which makes it unstable, so a pulseof energy is expelled from the nucleus - Fission Where a large atom decomposes intotwo smaller atoms and sometimes someother neutrons are released

Try Learn together, TSR's study area

182,399
essays

12,404
mindmaps

20,401
revision notes

10,285
quizzes

create
a study planner

thousands
of discussions

Study resources