Topic 5: Formulae, equations and amounts of substance Flashcards
an empirical formula shows
the smallest whole-number ratio of atoms of each element in a compound
a molecular formula shows
the actual number of atoms of each element in a molecule
the molar mass is
the mass per mole of a substance. it has the symbol M and the units g mol-1
a mole is
the amount of substance that contains the same number of particles as the number of carbon atoms in exactly 12g of the carbon-12 isotope
the avogadro constant is
the number of atoms of carbon-12 in exactly 12g of carbon-12, which is 6.02 x10 (23)
coefficients are
the numbers written in front of species when balancing an equation
spectator ions are
the ions in an ionic compound that do not take part in a reaction
hydrates are
compounds containing water of crystallisation, represented by formulae such as CuSO4 . 5H2O
avogadro’s law states that
equal volumes of gases under the same conditions of temperature and pressure contain the same numbers of molecules
molar volume is
the volume occupied by 1 mol of any gas
a solute is
a substance that is dissolved
a solvent is
a substance that dissolves a solute
a solution is
a solute dissolved in a solution
the mass concentration of a solution is
the mass (in g) of the solute divided by the volume of the solution
the molar concentration of a solution is
the amount (in mol) of the solute divided by the volume of the solution
a standard solution is
a solution whose concentration is accurately known
primary standards are
substances used to make a standard solution by weighing
the equivalence point is
the point at which there are exactly the right amounts of substances to complete the reaction
the end point is
the point at which the indicator just changes colour. ideally, the end point should coincide with the equivalence point
the meniscus is
the curving of the upper surface in a liquid in a container. the lowest horizontal part of the meniscus should be read
the tire is
the volume added from the burette during a titration
concordant titres are
those that are close together (usually 0.2 cm3 of each other)
an error is
the difference between an experiment value and the accepted or correct value
accuracy is
a measure of how close values are to the accepted or correct value
