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Dodaj cały arkusz do zestawuHeat treatment at 90 °C is used to destroy spoilage micro-organisms in pineapple juice. The concentration of vitamin C was measured over 56 days in untreated juice and in heat-treated juice from the same batch. (i) Identify the dependent variable in this…
Ultraviolet (UV) light is being investigated as a way of killing micro-organisms in juice without heating it, so that less vitamin C is lost. The absorption spectrum of a dilute aqueous solution of sorbic acid, a preservative that is added to some bottled…
The concentration of vitamin C and the pH of five fruit juices were measured. Use the data to deduce whether pH and the concentration of vitamin C are correlated, giving a reason.
The vitamin C content of a juice can be found by titrating a sample against a standard iodine solution. Starch is used as the indicator: it forms a dark blue-black complex with the first excess of iodine once all the vitamin C has reacted.…
Calcium hydride, CaH2, is an ionic compound that forms a crystalline lattice of Ca2+ and H− ions. Deduce whether calcium hydride behaves as a Brønsted–Lowry acid or as a Brønsted–Lowry base, and justify your answer.
The properties of a material depend on the way its atoms are bonded and arranged. Sheets of pyrolytic graphite, which consists of many stacked layers of carbon atoms, are used in some phones to spread heat away from the processor. A sheet conducts heat very…
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…
Palmitic acid, CH3(CH2)14COOH, and palmitoleic acid, CH3(CH2)5CH=CH(CH2)7COOH, which has a cis C=C double bond, both have a chain of sixteen carbon atoms. Predict which of the two fatty acids has the higher melting point and give two reasons for…
Name the hydrocarbon that is the main component of natural gas.
Outline one advantage and one disadvantage, other than cost, of burning natural gas instead of coal in a power station. Advantage: Disadvantage:
Benzocaine, a local anaesthetic, is the ethyl ester of 4-aminobenzoic acid. The crude product of its synthesis is purified by recrystallization. Discuss two ways in which the melting point of the recrystallized benzocaine can show that it still contains…
Magnesium hydroxide is used as an antacid to neutralize excess stomach acid, which is hydrochloric acid. Write an equation for the reaction between magnesium hydroxide and hydrochloric acid, including state symbols.