Chemistry Unit 1 definitions and formulas

Definitions Relative Atomic Mass- the average mass of an element (taking into account all isotopes) compared to the mass of an atom of Carbon-12 (NO UNITS!!!). Molar Mass- The mass of a single molecule on a scale on which the mass of an atom of Carbon-12 has a mass of 12 atomic mass units (UNITS = g mol-1) Isotope- an atom of an element with different atomic mass due to different numbers of neutrons. Avogadro Constant- the number of atoms in exactly 12g of Carbon-12. It is equal to 6.02x10^23. Enthalpy of Reaction- the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation, in their standard states under standard conditions. Enthalpy of Formation- the enthalpy change when 1 mole of a substance is formed from its constituent elements with all products and reactants in stand states under standard conditions. Enthalpy of Combustion- the enthalpy change when 1 mole of a substance is combusted completely with oxygen with all products and reactants in stand states under standard conditions. Enthalpy of Atomisation- the enthalpy change when 1 mole of an elements atom in the gaseous state is formed from the element under standard conditions. Enthalpy of Neutralisation- the enthalpy change when an acid and a base react together to form 1 mole of water under standard conditions Exothermic- If a reaction is exothermic the temperature rises and deltaH is negative because the system is losing energy. Endothermic- If a reaction is endothermic the temperature decreases and deltaH is positive because the system is gaining energy. Atom- the smallest, electrically neutral particle of an element that can take part in a chemical change. Molecule- the smallest, electrically neutral particle of an element or compound that can exist on it's own. Ion- an atom, or group of atoms, that carries an electrical charge.Calculations % yield= mass obtained/theoretical mass x100 Atom Economy= mass of wanted product/total mass of products x 100 % by mass= mass of solute/total mass of products x100 % by volume= volume of one compound/total volume x100 Concentration= mass of component/mass of solution x100 Mass= Mr x Moles Mass of moles= mass of 1 mole x number of moles mentioned Volume= moles x 24 (dm3) Moles= volume x concentration Concentration= moles/volume (/1000) (dm3) Avogadro Constant

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