Transition Metals: Properties and Comparisons with Alkali Metals

2. Transition Metals (Cr, Mn, Fe, Co, Ni and Cu) Are typical metals so have the usual properties but also… • Can have more than one ion E.g. Cu+ and Cu2+ and Fe2+ and Fe3+ • Form coloured compounds E.g. Potassium chromate (VI) is yellow and potassium manganate (VII) is purple • Make good catalysts. E.g. A nickel based catalyst is used in the hydrogenation of alkenes and an iron catalyst is used in the Haber process for making ammonia.

3. Transition Metals vs Alkali Metals • Alkali metals MORE REACTIVE than transition metals (i.e. Are more reactive with oxygen, water & halogens). • Transition metals are MORE DENSE, STRONG and HARD • Alkali metals have LOWER MELTING POINTS (The exception is mercury, which is a liquid at room temperature)

4. TOPIC 2 BONDING, STRUCTURE AND THE PROPERTIES OF MATTER

5. Sizes of Particles & Their Properties • Nanoscience refers to structures that are 1-100 nm in size, of the order of a few hundred atoms. • Nanoparticles are smaller than fine particles and coarse particles. Coarse particles are often referred to as dust. • As the side of a cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10.

6. Uses of Nanoparticles • Nanoparticles may have properties different from those for the same materials in bulk because of their high surface to volume ratio. • It may also mean that smaller quantities are needed to be effective than for materials with normal particles sizes. • Nanoparticles have applications in medicine, electronics, cosmetics, suncreams, as deodorants and as catalysts. • However there may be risks associated with the use of nanoparticles.

7. TOPIC 3 QUANTITATIVE CHEMISTRY

8. Concentrations in mol/dm3 Use this equation for titration calculations

9. What is the concentration, in mol/dm3, of a solution containing 3.7g of calcium hydroxide (Ca(OH)2)in 0.25dm3?

12. Question What mass of sodium hydroxide (NaOH, Mr = 40) is there in 0.450 dm3 of a 0.600 mol/dm3 solution?

13. Answer What mass of sodium hydroxide (NaOH, Mr = 40) is there in 0.450 dm3 of a 0.600 mol/dm3 solution? So mass of solute in mol = concentration x volume

14. Answer What mass of sodium hydroxide (NaOH, Mr = 40) is there in 0.450 dm3 of a 0.600 mol/dm3 solution? So mass of solute in mol = concentration x volume = 0.6 X 0.45 = 0.27 mol no. moles = mass So 0.27 mol = mass Mr 40 So mass = 0.27 x 40 = 10.8g

17. Titrations Burette: used to measure the volume of the solution added. Pipette: used to measure out a fixed volume of solution • Measure out 25cm3 of sodium hydroxide using a pipette. • Pour into the conical flask and add 3 drops of indicator. • Make sure the burette is filled to 0cm3 with acid. • Add the acid to the alkali until the indicator changes from pink to colourless • Now repeat, but when you get close to the endpoint add the acid dropwise. The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator.

18. Citric acid and sodium hydroxide titration exam question

19. Rearrange the equation to work out the moles of sodium hydroxide ( 2 known values No. moles sodium hydroxide used = conc. x volume = 0.102 x 25/1000 = 0.00255 moles NaOH From equation: No moles NaOH = 3 times no. moles citric acid.

20. 0.00255 moles NaOH From equation: No moles NaOH = 3 times no. moles citric acid. From equation: No moles NaOH = 3 times no. moles citric acid. So no. moles citric acid = 0.00255/3 = 0.00085

21. Concentration of citric acid = 0.00085/0.0121 = 0.07 mol/dm3

22. Sodium hydroxide & sulphuric acid titration calculation exam question

29. Moles of H2SO4= ( rearrange equation) 0.100 x 0.02712 = 0.00271 ( 1 mole) Moles of NaOH = 0.00271 x 2 =0.00542 Concentration of NaOH ( use the equation above)= 0.00542/0.025 = 0.2168 0.217 mol/dm3

32. No. moles = conc. X volume No. moles = 0.18 x 20/1000 = 0.0036 Mass = No.moles x Mr 0.0036 x 40 = 0.144g

33. *Another key equation to learn

34. Question 14 A solution of sodium hydroxide has a concentration of 80g/dm3. Calculate the mass of sodium hydroxide in 40 cm3 of solution.

35. Question 14 A solution of sodium hydroxide has a concentration of 80g/dm3. Calculate the mass of sodium hydroxide in 40 cm3 of solution. So mass = conc. X volume

36. Question 14 A solution of sodium hydroxide has a concentration of 80g/dm3. Calculate the mass of sodium hydroxide in 40 cm3 of solution. Mass = concentration x volume

37. Converting between mol/dm3 and g/dm3

38. Calculating Percentage Yield Percentage yield = Actual yield x 100 Theoretical yield E.g. In the previous reaction if we got 100% yield we would get 176g but if we only get 124g what is the % yield? 124/176 = 0.704 x 100 = 70.4%

39. Why not 100%?

40. Atom Economy

41. Volumes of Gases

42. Sodium carbonate reacts with dilute hydrochloric acid as follows: Na2CO3 + 2HCl 2NaCl + CO2 + H2O CHEMISTRY 1H SPECIMEN 2018 SET 1

44. TOPIC 4 CHEMICAL CHANGES

45. Cells and Batteries • Cells contain chemicals which react to produce electricity. • Voltage produced by a cell depends on: • Type of electrode (which metal) • The electrolyte • Batteries consist of 2 or more cells connected together in series to provide a greater voltage. • The bigger the difference in reactivity of the electrodes, the bigger the voltage of the cell. • No difference in reactivity = zero voltage.

46. Cells and Batteries Determining an Order of Reactivity If the right hand electrode is kept as copper and the left hand electrode is changed, the bigger the voltage, the bigger the difference in reactivity of the metal and copper, and so the more reactive the metal will be. Work out the order of reactivity from these results: Order of reactivity: Aluminium Zinc Tin Lead

47. Cells and Batteries • In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up. Alkaline batteries are non-rechargeable. • Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external current is supplied.

48. Fuel Cells • Fuel cells are supplied by an external source of fuel and oxygen or air. The fuel is oxidised electrochemically within the fuel cell to produce a potential difference. • Hydrogen fuel cells offer a potential alternative to rechargeable cells and batteries. The overall reaction involves the oxidation of hydrogen to produce water. 2H2 + O2 → 2H2O

49. Fuel Cells The reactions which occur at the electrodes are: • H2 → 2H+ + 2e- Oxidation • O2 + 4H+ + 4e- → 2H2O Reduction • The electrons flow through an external circuit from the anode to the cathode – this is the electric current.

50. Hydrogen Fuel Cell v’s Rechargeable Cell • Fuel cell vehicles don’t produce as many pollutants as other fuels - The only by-products are water and heat • Electric vehicles don’t produce many pollutants either but their batteries are much more polluting to dispose of than fuel cells because they are made of highly toxic metal compounds • Batteries in electric vehicles can be recharged – but only so many times before they need replacing • Batteries are more expensive to make than fuel cells • Batteries store less energy than fuel cells and so would need to be recharged more often – which can take a long time. • Once you’ve got the hydrogen, fuel cells are eco-friendly but producing hydrogen takes a lot of energy (usually from burning fossil fuels!)