Concentrated hydrobromic acid, HBr(aq)\text{HBr(aq)}HBr(aq), can be electrolysed using inert electrodes.
Write a balanced ionic half-equation for the formation of hydrogen gas, H2\text{H}_2H2, at the negative electrode (cathode).
During the electrolysis, a volume of 54 cm354\text{ cm}^354 cm3 of hydrogen gas, H2\text{H}_2H2, is collected at the negative electrode (cathode).
Calculate the amount, in moles, of hydrogen gas in 54 cm354\text{ cm}^354 cm3. (The volume of 1 mol1\text{ mol}1 mol of any gas at room temperature and pressure is 24 000 cm324\,000\text{ cm}^324000 cm3.)
Calculate the quantity of electricity, in coulombs, needed to produce this volume of hydrogen gas from the half-equation:
2H++2e−→H2 2\text{H}^+ + 2\text{e}^- \rightarrow \text{H}_2 2H++2e−→H2(1 faraday=96 500 coulombs1\text{ faraday} = 96\,500\text{ coulombs}1 faraday=96500 coulombs)
Bromine gas reacts with potassium iodide solution. The equation for this reaction is:
Br2(g)+2I−(aq)→2Br−(aq)+I2(aq) \text{Br}_2(\text{g}) + 2\text{I}^-(\text{aq}) \rightarrow 2\text{Br}^-(\text{aq}) + \text{I}_2(\text{aq}) Br2(g)+2I−(aq)→2Br−(aq)+I2(aq)This reaction can be described as both a displacement reaction and a redox reaction.
Identify the element that is displaced in this reaction.
Explain why this reaction is described as a redox reaction in terms of electron transfer.
Chlorine is also used in the industrial manufacture of phosphorus pentachloride, PCl5\text{PCl}_5PCl5. The equation for this reaction is:
PCl3(g)+Cl2(g)⇌PCl5(g)ΔH=−88 kJ/mol \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g}) \rightleftharpoons \text{PCl}_5(\text{g}) \quad \Delta H = -88\text{ kJ/mol} PCl3(g)+Cl2(g)⇌PCl5(g)ΔH=−88 kJ/molWhat does the ⇌\rightleftharpoons⇌ symbol indicate about this reaction?
Predict and explain the effect of increasing the temperature on the equilibrium position of this reaction.
