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Steel Story Lesson 2 – moles in gas and solution(synoptic)

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Objectives Must Recall the molar volume of gases at STP and RTP Should Carry out calculations involving gas volumes, concentrations of solutions, volumes of solution and moles Could Calculate reacting volumes of gas in balanced equations

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Starter

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Specification statements Use the concept of amount of substance to perform calculations involving; Molecular formulae, Masses of reagents, Percentage yields, Volumes of gases, Volumes of solutions of known concentrations, Balanced chemical equations

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Theory – moles of gas

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What is 24 dm 3 ? This is about the size of a beach ball It is interesting that the molar volume is the same for every gas.

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Questions – finding moles Find the number of moles of molecules in the following gaseous volumes at room temperature; a)240 cm 3 of Helium b)480 cm 3 of carbon dioxide CO 2 c)480 dm 3 of sulfur dioxide SO 2 d)1200 cm 3 of methane CH 4 e)1.2 cm 3 of propane C 3 H 8

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Answers a)Moles = (240/1000)/24 = 0.010 mol b)0.020 mol c)20 mol d)0.050 mol e)0.000050 mol or 5.0 x 10 -5 mol

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Questions – finding volumes What is the volume occupied by each of the following gases at room temperature; a)4.0g of hydrogen molecules H 2 b)3.2g of methane CH 4 c)0.00048g of ozone O 3 d)17.6kg of carbon dioxide CO 2 e)6.8 tonnes of ammonia NH 3

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Answers Moles = massmoles = volume Mr24 (RTP) a)Moles of H 2 molecules = 4.0g/2 = 2 mol volume = moles x 24 = 2 x 24 = 48 dm 3 b)4.8 dm 3 c)0.24 cm 3 d)9600 dm 3 e)9,600,000 dm 3

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AfL – using whiteboards 1.Find the number of moles of molecules in 96cm 3 of uranium (VI) fluoride. Show your working 2.What is the volume occupied by 4.0g of Argon atoms

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Answers 1.0.0040 mol 2.2.4 dm 3

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Calculation – reacting volumes

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Group work

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Answer

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Exam question

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Answers with indicative marks

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Exam question In 2000, the mass of CO 2 emitted in the UK was equivalent to 1 kg per person in every hour. (i)Calculate the volume of 1 kg of carbon dioxide. Assume that 1 mole of CO 2 occupies 24 dm 3. volume =.......................... dm 3 [2] (ii)The UK has set a target to cut CO 2 emissions by 60% of the 2000 value by 2050. Calculate the reduction needed in the volume of CO 2 emissions each hour per person if the target is to be met. answer:........................... dm 3 [1] [Total 3 marks]

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Answer

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Theory – concentration of solutions

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Questions Calculate the number of moles present in each of the following; a)25.0 cm 3 of 0.1 moldm -3 hydrochloric acid b)1.5 dm 3 of 2.5 moldm -3 sodium hydroxide c)3.0 cm 3 of 2.0 moldm -3 sulfuric acid d)20.0cm 3 of 0.17 moldm -3 barium hydroxide e)11.2cm 3 of 0.5 moldm -3 sodium carbonate solution

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Answers a)25.0/1000 x 0.1 mol = 0.0025 mol b)3.75 mol c)0.006 mol d)0.0034 mol e)0.0056 mol

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Exam question

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Answers

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Summary Recall the molar volume of gases at STP and RTP Calculate reacting volumes of gas in balanced equations Carry out calculations involving gas volumes, concentrations of solutions, volumes of solution and moles

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