Titration counts: One mole – can you imagine?

1. Titration counts: One mole – can you imagine? • Since Avogadro and Loschmidt we call 6 . 1023 atoms or molecules one mole of a substance. One mole = 602213673600000000000000 particles. • Can you imagine what that means? - One mole of marbles spreaded on the globe would form a layer of 3 km thickness - Assuming that a computer could count 10 Million molecules in one second, it would need 2 trillions of years to count one mole of them - One mole of dollar 100 Euro-bills stacked on top of each other would fill the distance Sun-Pluto 7,5 million times http://www.unit5.org/christjs/Stoichiometry/The%20Mole%20Concept.ppt#262,6,Careers in Chemistry – Philosopher CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21

2. Titration is what counts: More images to represent one mole • Assuming that each human being has 60 trillion body cells (6.0 x 1013) and the Earth's population is 6 billion (6 x 109), the total number of living human body cells on the Earth at the present time is 3.6 x 1023or a little over half of a mole. • If one mole of pennies were divided up among the Earth's population, each person would receive 1 x 1014 pennies.  Personal spending at the rate of one million dollars a day would use up each persons wealth in about three thousand years.  Life would not be comfortable because the surface of the Earth would be covered in copper coins to a depth of at least 400 meters. http://lvstem.cse.lehigh.edu/teams/freedom/The%20Mole-intro-actvity-lesson%20plan.doc • Each screw in a package of screws and nuts corresponds to one nut – an analogy for the reaction of monoprotic acid with e.g. NaOH-solution CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21

3. Titration is what counts • When you weigh, you count molecules – 60 g of acetic acid contain one mole of molecules • When you now dilute or dissolve the acid, you have a defined number of molecules in a given volume • When you now titrate this solution to check the molarity, with e.g. NaOH-solution, you react the number of acetic acid molecules contained in the volume of solution with the base. If the hydroxide ion content of the NaOH-solution is known, you can calculate the concentration of the acid from the volume of base needed to reach the equivalence point. • Titration is a rapid, inexpensive and highly precise (and accurate) method for the determination of analytes – and it does not need calibration. CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21

4. Experiment: • Titration of household vinegar to measure the acetic acid content with sodium hydroxide solution • Phenolphthalein is used as an indicator to mark the equivalence point • The volume of hydroxide solution is used to calculate the acid concentration in the vinegar http://www.dkimages.com/discover/previews/890/25053821.JPG CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21

5. The equivalence point of the titration of vinegar with NaOH lies in the alkaline region, because the resulting salt sodium acetate is the salt of a weak acid and a strong base – hence it shows an alkaline reaction (pink colour of the solution containing phenolphtaleine as an indicator) “one nut for each screw“ phenolphthalein is colourless in the acidic and pink in the basic region CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21