chem unit 3 pt 2

practical 1

measure the molar volume of a gas

how to measure volume of gas released

glass syringe

disadvantages of using glass syringe

some gas escapes before bung is placed, some gases react with water

reactants in practical one

ethanoic acid and calcium carbonate

practical two

determine the enthalpy change of a reaction using Hess' Law

why is it not possible to measure enthalpy change directly

heat energy must be supplied, not all the energy is decomposition

why are reactions conducted in a polystyrene cup

better insulator, less heat lost to surroundings

practical 3

finding concentration of hydrochloric acid via titration

concordant results

within 0.2 of each other

why use larger titres

the percentage uncertainty is higher for small values

practical four

preparing a standard solution from solid acid

solid acid used in practical 4

solid sulfamic acid, mix with 100 cm3 of water

why should the pipette be washed with NaOH after water

no leftover water, less precise

methyl orange

red in acid, yellow in alkali

phenolphthalein

pink in alkali, clear in acid