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

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

Starter

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

Theory – moles of gas

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.

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

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

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) g of ozone O 3 d)17.6kg of carbon dioxide CO 2 e)6.8 tonnes of ammonia NH 3

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

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

Answers mol dm 3

Calculation – reacting volumes

Group work

Answer

Exam question

Answers with indicative marks

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 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]

Answer

Theory – concentration of solutions

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

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

Exam question

Answers

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