Edexcel A-level Chemistry Essential Practical’s Methodologies with Expected Solutions. Verified for new updates

Core practical 1 - measuring the molar volume of gas METHOD [7] METHOD: 1. known volume of ethanoic acid in boiling tube 2. place 0.05g of calcium carbonate in test tube 3. weigh contents 4. tip contents into ethnic acid and seal with bung 5. measure volume of gas produced, collected in a measuring cylinder over a water bath 6. Reweigh the test tube 7. Repeat experiment increasing the mass of calcium carbonate by 0.05g each time. do not exceed 0.4g of calcium carbonate core practical 1 - measuring the molar volume of gas REACTANTS USED FOR THIS EXPERIMENT [2] ethanoic acid and calcium carbonate core practical 1 - measuring the molar volume of gas MAIN SOURCE OF ERROR OF THIS PROCEDURE AND ADJUSTMENT TO ERADICATE ERROR main source of error: loss of gas during the time taken to replace the bung adjustment: put ethanoic acid in test tube in a vessel so the contents can be tipped into an already sealed system. core practical 1 - measuring the molar volume of gas why should you not exceed 0.4g of calcium carbonate? a mass above 0.4g will result in the volume of gas produced exceeding the capacity of the measuring cylinder core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH METHOD METHOD: 1. weigh empty test tube. scoop 2.5g of sulfamic acid into test tube and reweigh. 2. dissolve sulfamic acid in ~100cm3 of water in a beaker 3. Transfer solution and washings into volumetric flask and make solution up to mark with distilled water 4. prepare apparatus for titration. Burette contains acid, conical flask contains NaOH. 5. pour an aliquot of NaOH of unknown concentration into conical flask. 6. use methyl orange as indicator 7. Titrate contents until 2 concordant titres have been achieved core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH INDICATOR USED methy orange core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH how to calculate percentage error of a 250cm3 volumetric flask with an accuracy of +- 0.6cm3 accuracy/volume (0.6/250) x 100 = +-0.24% core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH TYPE OF EXPERIMENT titration core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH Why must the pipette be rinsed with sodium hydroxide after washing it with water? Water that is left in the pipette will dilute the NaOH solution, changing the number of moles used. core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH Why is there no need to dry the conical flask after washing between trials? water will not change the number of moles of NaOH in the conical flask because the volume has already been measured. core practical 2 - preparing a standard solution from a solid acid and using it to find the concentration of solution of NaOH name a different indicator that could be used for th