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Liquid octane burns completely in oxygen to give carbon dioxide and liquid water. C8H18(l) + O2(g) → CO2(g) + H2O(l) What is the C8H18 : O2 ratio when the equation is balanced using the smallest whole-number coefficients? A. 1 : 12 B. 1 :…
The enthalpy changes of two reactions of the gases involved are known: ΔH1 = −548.8 kJ mol−1…
Deduce the shapes of the CO2 and H2O molecules and explain why they differ.
Iron has a number of natural isotopes. A sample of iron was enriched in to produce a mixture with the following composition: (i) Calculate the relative atomic mass of the enriched sample, giving your answer to two decimal places. (ii) Natural…
A student electrolysed aqueous silver nitrate between two silver electrodes, as shown. Each electrode was washed, dried and weighed before and after the electrolysis. Suggest why the mass gained by the cathode is a less accurate measure of the amount of silver…
Thallium (Ar = 204.38) consists of two stable isotopes, and . What is the relative abundance of ? A. 31 % B. 38 % C. 62 % D. 69 %
Aluminium has a low density, which is why it is widely used in aircraft and in specialized alloys. Aluminium is produced industrially by the electrolysis of aluminium oxide dissolved in molten cryolite, as shown in the diagram. (i) Outline why the molten…
A biochemist is analysing a protein extracted from soya beans. A sample of the protein is completely hydrolysed to a mixture of amino acids. Outline how paper chromatography can be used to identify the amino acids in this mixture when samples of the pure amino…
Naturally occurring bromine has Ar = 79.90 and contains only the isotopes 79Br and 81Br. What percentage of the atoms are 81Br? A. 10 % B. 45 % C. 55 % D. 90 %
Aluminium is a low-density metal that is used in lightweight alloys. Aluminium is produced by the electrolysis of molten aluminium oxide (in industry dissolved in molten cryolite to lower the operating temperature). A simplified cell is shown in the diagram.…