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All the species in the titration are almost colourless except MnO4−, which is intensely purple. The spinach extract, however, is coloured green by chlorophyll. (i) State the colour change at the end point. (ii) Outline how adding distilled water to the…
State the class of error that always shifts the results of an experiment in the same direction.
The end point was reached after 3.0 ± 0.1 cm3 of titrant had been run in. (i) Calculate the percentage uncertainty in this titre. (ii) Suggest one change to the procedure that would lower the percentage uncertainty of a single titration, apart from…
The result is roughly 30 times higher than the iron content of spinach given in reference tables (as a percentage by mass). Suggest one reason, apart from human error, for so large a difference.
Magnesium ribbon of known mass was heated strongly in a crucible, and the heating was repeated until the mass no longer changed. The final mass of the solid was then recorded. Assume that magnesium oxide is the only product. Which of the following can be…
Halogenoalkanes form a homologous series. (i) Outline the meaning of homologous series. (ii) State the preferred IUPAC name of each of the two compounds shown. (iii) But-1-ene can be polymerized. Draw a section of the resulting polymer showing two repeating…
Iron is extracted in a blast furnace by reducing iron(III) oxide with carbon monoxide. Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g) Calculate the percentage atom economy for the production of iron by this reaction. Use section 1 of the data booklet.
50 cm3 of gas X reacts with 20 cm3 of gas Y to form 20 cm3 of a gaseous product and leaves 10 cm3 of X unreacted. All volumes are measured at the same temperature and pressure. What is the empirical formula of…
Molten lithium bromide, LiBr(l), is electrolysed using inert graphite electrodes, as shown in the diagram. (i) Identify the product formed at the cathode. (ii) State the direction in which the electrons flow in the external circuit, referring to the…
The concentration of dissolved oxygen in a sample of pond water was determined by the Winkler method. The reactions that take place are:…