Amount of Substance Flashcards
Define Relative Atomic Mass
The average mass of an atom of an element (taking into account its naturally occurring isotopes) relative to 1/12th of the relative atomic mass of a carbon-12 atom.
What is the Avogadro Constant?
6.022 × 10^23
Define Relative Molecular/Formula Mass
The average mass of a molecule/compound (taking into account its naturally occurring isotopes) relative to 1/12th of the relative atomic mass of a carbon-12 atom.
What is the equation involving moles, mass and Mr?
Moles = Mass/Mr
What is the equation involving moles, concentration and volume?
Concentration = Moles/Volume
What is the Ideal Gas Equation?
PV = nRT
P - Pressure (Pascals)
V - Volume (m3)
n - Moles
R - Gas Constant (8.31)
T - Temperature (Kelvin)
What is the empirical formula?
The whole number ratio of elements in a compound, may not be the actual amount of elements in the compound.
What is the molecular formula?
The true number of each element in the compound.
How do you calculate the molecular formula?
Divide the ACTUAL Mr of the compound by the Mr of the EMPIRICAL FORMULA. Use this multiplier to scale up the empirical formula.
How do you calculate empirical formula?
- Find the mass or % of each element in the compound.
- Divide each value by the relative atomic mass of its element.
- Put them into a ratio and divide all values by the smallest number (in order to have a 1).
- IF RATIO, close to 0.5, multiply by 2, close to 0.34/0.33, multiply by 3.
What is the equation for Percentage Yield?
100(Actual Mass Made/Theoretical Mass)
What is the equation for Atom Economy?
100(Mr of desired product/Mr of reactants)
Give an economic, environmental and ethical advantages for having a high atom economy.
Little to no waste product, means less money wasted and less natural resources used up (often less energy)
REQUIRED PRACTICAL 1
Make up a volumetric solution and carry out a simple acid–base titration.
What is the method for making a standard solution?
- Measure mass of dry weighing boat on weigh scale. Use a spatula to add the known mass of the soil. Measure mass of weighing boat with solid. To 2 d.p.
- Put solid from weighing boat into beaker and reweigh empty boat again (weight of weighing boat with solid - weight of weighing boat alone = mass of solid added to beaker).
- Add a little bit of deionised water to dissolve solid and stir with stirring rod.
- Transfer solution to a volumetric flask with the funnel.
- Add deionised water with pipette (dropwise at end) until the meniscus reaches the line.
- Put stopper on volumetric flask and invert a few times to ensure proper mixing.