The police offen make use of breathalysers to measure the amount of alcohol in a porson's systom, to ensure drivers are under the legal limit of intoxication. Different types of broathalyser have been invented, many of which use spectroscopy. In one type of breathalyser, when a driver breathes into the breathalyser machine, the ethanol molecules in their breath react with acidified potassium dichromate in the breathalyser. QUESTIONS: 1. a) write a balanced half equation for the oxidation of ethanol (C2H5OH) in the driver's breath [2 marks] b) write a baianced half equation for the reduction of dichromate (Cr2O72−) in the breathalyser machine (2 marks) c) write the overall redox equation for the reaction occurring inside the breathalyser machine [2 marks] 2. Suggest a colour of light that the breathalyser could be designed to measure, which is related to the occurrence of this reaction. Explain your choice. [2 marks]
Sodium chloride is a highly soluble salt. It is possible to make a saturated solution of sodium chloride - this means dissolving as much sodium chloride as possible into water: NaCl(s)⇌Na(aq)++Cl(aq)− At room temperature, it is possible to dissolve a total of 18.0 g of sodium chloride in 50.0 mL of water before the solution becomes saturated. During this process, the solution becomes colder; dropping in temperature from 25.0∘C to 19.3∘C. I QUESTIONS: 1. Calculate the standard enthalpy of solution of sodium chloride [3 marks] 2. a) Write an expression for the solubility product, Ksp for sodium chloride. [1 mark] b) solve the value of Ksp [2 marks]
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