- 1 10 Phenanthroline O Phen In The Picture To The Left Is A Compound That Reacts With Metals Such As Iron Nickel Rut 1 (244.43 KiB) Viewed 44 times
1,10-phenanthroline (o-phen) in the picture to the left, is a compound that reacts with metals such as iron, nickel, ruthenium, and silver to form strongly colored complexes. This property provides an excellent and sensitive method for determining these metal ions in aqueous solution. For example, o-phen reacts with ferrous (Fe²) ion to produce a deeply colored red complex: Reaction 1: Fe²+ 30-phen = Fe(o-phen)s Hydroxylamine, as its hydrochloride salt will make the ferrous iron. Reaction 2: 2Fe³+ + 2NH₂OH+ 20H 2Fe²+ + N₂ + 4H₂0O This is an equilibrium reaction, but even a mild reducing agent will drive it >99.99% to the right. The pH is adjusted to a value between 6 and 9 by addition of an ammonia or acetate buffer. The molar absorptivity (e) of the ferrous complex is 11,100 L/mol-cm at the wavelength of maximum absorbance intensity, A= 508 nm. This large value indicates the complex absorbs very strongly. The intensity of the color is independent of pH in the range of 2-9. The complex is very stable and the color intensity does not change appreciably over long periods. Beer's law is obeyed, over about 1.5-2 orders of magnitude of iron concentration. In this lab, you will be determining the equilibrium constant for the Fe(o-phen); complex. You will need to pre-determine your equilibrium mixtures of how much Iron standard you will mix with pre- determined amounts of o-phen, buffer, and hydroxylamine. A standard curve for the complex has already been made for you and given below and will be used when performing your analysis.
answers Home Study tools ✓ My courses ✓ My books My folder Fe 1,10- phenanthroline Beers law 0.8 0.6 0.4 y=11330x +0.0018 R² = 0.9996 0.2 0.00001 0.00002 0.00003 0.00004 0.00005 0.00006 0.00007 0.00008 Molarity of iron phenantroline Table 2 (middle of photograph) Your predetermined molarity values of the Fe²+ must fall within the molarity range from the standard curve (see the graph). You will need to make three different equilibrium mixtures that have a different iron concentration for each. The stock iron solution you will use to dilute from will have a concentration about 1. x 10-4 M Fe²+. You will need to use the true concentration that is listed on the bottle for your calculations when finishing the lab write up. Where will you find the concentration of the o-phen? You must have iron volumes determined before starting the practical, and written procedures before you start the practical. Show your instructor your iron volumes at the beginning of the lab. Each mixture will contain: hydroxamine (mL) o-phen (mL) total volume (mL) Fe (ml) Buffer (mL) 1 5 Dilute to mark 50 5 Dilute to mark 1 5 Dilute to mark You will need to add the chemicals in this order: 1. Iron Absorbance 1 50 50 Career Life