quantitative chemistry

• The law of conservation of mass states that no atoms are lost or made during a chemical reaction
• the mass of the products equals the mass of the reactants
• The relative formula mass (Mr ) of a compound is the sum of the relative atomic masses of the atoms shown in the formula.
• Reactions that may appear to have a change in mass can usually be explained by the reactant/product being a gas, and the mass has not been taken into account.
• When a metal reacts with oxygen, the mass of the oxide produced is greater than the mass of the metal.
• to calculate uncertainty... $uncertainty=$$range/2$
• The mass of one mole of a substance in grams is numerically equal to its relative formula mass.
• The number of atoms, molecules, or ions in a mole of a given substance is the Avogadro constant.
• The value of the Avogadro constant is 6.02 x 10^23 per mole.
• to find the number of mols... $mols=$$mass/mr$
• to find the mass... $mass=$$moles*$$mr$
• The reactant that is completely used up is called the limiting reactant because it limits the amount of products.
• the greater the amount of moles (or mass of grams) in the limiting reactant, the greater the amount of moles (or mass of grams) in the products.
• to convert from g/dm^3 to mol/dm^3, divide by the Mr
• to convert from mol/dm^3 to g/dm^3, multiply by the Mr
• concentration = moles/volume
• volume= moles/concentration
• the higher the mass of the solute, the higher the concentration, for a given volume.
• it is not always possible to obtain the calculated amount of a product, since the reaction may not be completed due to it being reversible. some of the product may be lost when it is separated from the reaction mixture, and some of the reactants may react in ways different than expected.
• % Yield = Mass of product actually made /Maximum theoretical mass of product × 100
• Atom economy is a measure of the amount of starting materials that end up as useful products.
• It is important for sustainable development and for economic reasons to use reactions with a high atom economy.
• Atom economy= Relative formula mass of desired product/Sum of relative formula masses of all reactants × 100
• The higher the mass of the solute in comparison to the volume of the solution, the higher the concentration.
• Equal amounts in moles of gases occupy the same volume under the same conditions of temperature and pressure.
• The volume of one mole of any gas at room temperature and pressure (20oC and 1 atmosphere pressure) is 24 dm^3 .
• vol of gas at room temp = mols x 24