Required Practicals

prep: Filter solution gravity before 1) Dissolve impure crystals in the minimum volume of hot solvent 2) Filter off hot solution by gravity filtration , using a hot funnel and fluted filter paper - prevents precipitation of solid 3) Allow the solution to cool and crystallise - scratch side of flask with a glass rod 4) Filter off crystals formed using suction filtration under reduced pressure 5) Wash by pouring some iced cold solvent too remove aqueous impurities 6)Dry by sucking air over the crystals in the büchner flask then place in a low temperature oven

1)Place some of the solid in a capillary tube sealed at one end 2) Place in melting point apparatus and heat gently 3) Record the temperature at which the solid starts to melt and the temperature at which it finishes melting 4) Repeat steps 1-3 and average the temperatures 5) Compare the melting point with know value as in the data book 6) If the compound melts at a lower melting point and over a range of temperatures, it is impure

. Some of the solid is lost in purification steps, some of the solid may still be dissolved in the solvent in recrystallisation .Some of the product is lost ion transferring solids between vessels (solved by rinsing to minimise loss)

ensures your readings are accurate and repeatable ph meter can be contaminated, so results tend to drift from their true value with further use

testing buffer solutions of known ph using that data to form a calibration curve map recorded ph’s to the calibration graph and read off their corrected ph values

Continuous monitoring method ie. Loss of reactant over time / Gain of product over time Initial Rates method (Iodine clock)

Plot a graph for each of the experiments at different Conditions Draw a tangent to the curve when x=0 Measure the gradient of this tangent The gradient is the initial rate of reaction, compare values with other graphs at different temperatures

The I2 produced reacts with the thiosulphate Excess I2 that remains in solution then reacts with starch to form a blue black solution Time how long it takes for the blue black colour to appear Vary the [I-] to then determine the order of the reaction with respect to iodine ions

Some [I-] conc may take too long to react Delayed stopwatch reactions makes readings inaccurate Concentrations may not be exact due to measuring apparatus

Measuring change in concertation of reactant or product over time Involves measuring a quantity such as volume at set time intervals

Continuous monitoring method connect each end of rubber lead to a bung at one end and a gas syringe at the other add 6cm strip of magnesium ribbon into a conical flaks containing HCL quickly place a bung in the top of the flask and start the timer Note down Volume of hydrogen gas collected every 15 seconds Repeat using different Concentrations of HCl

Plot a graph of volume gas produced (Y-axis) against time (x-axis) for each different concentation of HCl Draw a tangent to the curve when x=0 Measure the gradient of this tangent The gradient is the initial rate of reaction, compare values with other graphs at different Concentrations

Some gas mat escape before the bung is added Density of magnesium ribbon used maybe different for each experiment

Two different half cells, connected by a salt bridge. with their electrodes connected by a high resistance voltmeter It’s electric potential energy is generated by chemical redox reactions

A connection between the half cells that allows the movement of ions, to complete the circuit. Consist of a concentrated electrolyte that doesn’t react with wither half cell solution

Graphite/ Platinum Unreactive with solutions & a good electrical conductor so doesn’t affect voltmeter readings

File the surface of a piece of copper & the other metal using emery paper connect the filed copper to the positive voltmeter terminal Cut a piece of filter paper, saturate it with KNO3 solution and place on top of copper covering it completely Connect voltmeter to another piece of metal Hold metal against the filter paper and record the voltmeter value , make sure none of the metals are directly touching Repeat with different metals and record results

Removes the oxide layer on the outside of the metal that is largely unreactive

Proton Donor Proton acceptor A bace that dissolves in water

To detect when a reaction reaches the end point, usually by the presence of a distinct colour change

the more accurate the data, the closer it is to the true value

Add 2Cm^3 of NaOH from a burette to ethanoic acid in a conical flask Continue to add 2cm^3 of NaOH measuring the ph each time

So all the acid and bace is thoroughly mixed Makes sure ph doesn’t significantly vary at different areas within the solution Gives a more accurate reading