R2.1: How much?

• Percentage yield is the actual/experimental yield divided by the theoretical yield, times 100
• Random errors are concerned with precision and has to do with flaws in tools. Systematic errors are concerned with accuracy and have to do with flaws in the methodology
• Residue in experiments make actual yields lower than theoretically predicted. If they are more, something is being added to the system (ex. impurities)
• Theoretical yield is calculated by taking the value of limiting reactant and multiplying it with the mole ratio of the product over the reactant, then multiplying it to its molar mass to turn it into grams
• Two ways to find limiting reactants?

  a ) Find the theoretical yield of product created by each reactant value. The one with the smallest yield is limiting reactant

  b ) Convert grams to moles and divide by their coefficient. Then compare the resulting values as the smaller one is the limiting reactant
• Atom economy is a measure of how much of the reactants are used to form the actually desired product- considers the materials used to make "waste products"
• After considering the Law of Conservation of mass that states that mass cannot be destroyed, only transferred- atom economy is calculated by dividing the molecular mass of the desired product (after multiplying with coefficient) over the molecular mass of all the reactants (after multiplying with coefficient), times 100.
• The volume of any ideal gas is 22.7 dm3 mol−1, and this can be used to divide dm3 volumes to find moles
• Homogenous reaction = all reactants + products in same state
• Heterogeneous equilibrium --> solids, liquids + aqueous never included in formula for Kc (equilibrium constant)
• Spontaneity --> the ability to start a reaction without any additional energy, or to start a reaction without any external stimulus. Very low spontaneity means the reaction needs a great amount of support to start their reaction or simply cannot do it at all
• When Gibbs = positive, reverse reaction favored, non-spontaneous

  When Gibbs = negative, forward reaction favored, spontaneous

  When Gibbs = 0, equilibrium
• Calculate the Mr of each carbonate and oxide.Magnesium carbonate has an Mr of ~84 g mol–1 and magnesium oxide has an Mr of ~40 g mol–1. This indicates the ratio of the mass being lost when 1 mole reactant is converted to 1 mole product (almost half). Apply that same ratio to the 10.0 g you are given to find the metal carbonate which would lose the most mass

  
• If a reaction asks for an amount, leave your answer in moles
• Condensation is an exothermic reaction
• Bond breaking is endothermic and is usually for reactants