Relative Atomic Mass: The average mass of one atom of an element relative to 1/12th the mass of one atom of C-12
Relative Formula Mass: (A1 x M1) + (A2 x M2) / TotalAbundance
Ideal Gas Equation:
PV = nRT
Empirical formula = The simplest ratio of atoms of each element in a compound
The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12
Alkali is usually in the conical flask in titration
What is the main safety precaution in titration? Wear eye protection and gloves (acids and alkalis are corrosive)
Why do we use a conical flask over a regular beaker? It is easier to swirl the mixture without spilling the contents
Water does not affect the titration as it doesn't change the number of moles of each reactant
How many titrations should we carry out? (at least) 3
What are the colour changes for phenolphthalein and methyl orange?
Phenolphthalein [pink (alkaline) to colourless (acid)]
methyl orange [yellow (alkali) to red (alkali)]
Using phenolphthalein vs methyl orange:
Use Phenolphthalein if NaOH is used
Use Methyl Orange if HCl is used
How can you reduce uncertainties in titration?
Replacing measuring cylinders with pipettes / burettes which have lower apparatus uncertainty
Increasing the volume and concentration of the substance in the conical flask to increase the titre volume
White tiles are used during titrations because you can more easily see the colour changes and end points
Empirical formula: The simplest whole number ratio of atoms of each element in a compound
Theoretical yield: The mass of product that is calculated and should have formed in a reaction. This is calculated using masses of reactants and a balanced equation.
How do you calculate percentage yield? Percentage Yield = Actual Yield / Theoretical Yield x 100
Percentage yield indicates how wasteful a process is, as it determines how much of the product is lost
Atom economy: A way determining how wasteful a reaction is. Atom economy is a measure of the proportion of reactant atoms that become part of the desired product, rather than by-products
Reasons why high atom economy is beneficial:
High atom economy is desirable for industrial processes.
They are better for the environment as they produce less waste
More efficient use of raw material means high atom economy is sustainable
How can we remove water of crystallisation in compounds? by heating, they can be removed as water vapour
Errors involved in using a gas syringe:
gas escapes before bung inserted
syringe sticks
some gases (e.g. CO2) are soluble in water so true amount isn't measured
Calculating volumes of gases reacting:
equal volumes of gases under same conditions will have equal moles
so the, ratio of volumes = ratio of moles
Steps to work out what reactant is in excess:
Calculate amount of each reactant in mols
Use balanced equation to work out which is in excess
use the limiting reactant for calculations
Avogadro constant: Number of particles/atoms/ions in one mole of a substance
Equation that links mass of 1 mol, mass of 1 atom and Avogadro constant:
Mass of 1 mol = mass of 1atom/molecule X Avogadro constant
Percentage yield: The % of a product produced by a reaction, compared to a theoretical maximum
Calculate percentage yield: Mass of useful product ÷ expected mass of useful product
What can the percentage yield of a practical be used to investigate? Efficiency of practical techniques and whether reactions proceed as estimated
Atom economy: % of amount of reactants made into a certain (useful) product
What can the atom economy of a reaction be used to investigate? Efficiency of using a specific reaction to produce a product
How do you convert between K and C temperatures?
°C to K+ 273
K to °C - 273
What is the equation that links moles, mass and Mr? Moles = mass / Mr