6.1.2

6.1.2 Describe suitable experimental procedures for measuring rates of reactions

Experimental Method	Dependent and Independent variables	Diagram	Additional Notes
Change in volume of gas produced	Independent: time (sec) Dependent: volume of gas (cm3)		Gas syringe best because inverted measuring cylinder or burette limited to gases with low solubility
Change in mass	Independent: time(sec) Dependent: mass of reactants(g)		Unlikely to work well, because there might not be a significant decrease in mass for example hydrogen is too light
Change in transmission of light: colorimery/ spectrophotometry	Independent: time(sec) Dependent: light intensity		Only works with coloured compounds, as the concentration of compounds increases, more light is absorbed therefore less is transmitted
Change in concentration measured using titration	Independent: time(sec) Dependent: concentration (cm3)		It cannot be done continuously thus samples must be taken from the reaction mixture. To avoid the mixture over reacting, a method called “quenching” can be used which provides a snap shot at the moment it is withdrawn.
Change in concentration measured using conductivity	Independent: time(sec) Dependent: electrical conductivity		As reactants are converted into products, there’s a sharp decrease in the electricity conductivity as there’s a decrease in the concentration of ions
Non-continuous methods of detecting change during a reaction:”clock reactions”	Independent: time(sec) Dependent: a magnesium ribbon disappearing or a cross view is no longer visible		It is more convenient to measure the time it takes for a reaction to reach a choosen fixed point