Balancing An Equation Experimentally CHEMISTRY 1105

Introduction Experimentally Balance: __KMnO 4 + __H 2 C 2 O 4 +__H + → __Mn 2+ + __CO 2 + __K + +__H 2 0 How Much Of Each Reagent Is Needed To React Fully With The Other ◦Reactant Coefficients ◦Begin With Either Reagent

Potassium Permanganate Avoid Skin Contact ◦React on skin to produceMnO 2 ◦Ugly Brown ◦Takes 3-4 days to be removed naturally

Oxalic Acid H 2 C 2 O 4 Colorless and Odorless Poisonous!!! Fatal; removes calcium from the body forming crystals in the kidney Irritant To Eyes, Skin, Respiratory

Questions What Is A Solution? How Is The Amount Of A Solute In A Solvent Determined? ◦Molarity = Molecules in solution Solute (salt) Solvent (Water) Solution = Salt + Water

Discussion How Is The End Of A Reaction Determined? ◦Several Ways but… ◦What if RXN is colorless? ◦indicator Add H 2 C 2 O 4 Until Color Disappears Which Way Is Better ◦See color appear or disappear? ◦Better to see color appear! ◦This Is The End Point Titration!!!

The burette Pay Very Close Attention Or Take Notes Burette demonstrate the use of noting each of the following areas ◦Barrel ◦Stopcock ◦Delivery Tube

Cleaning burette Rinsing YOUR DESK NOT THE SINK AREA ◦Get ONLY what you need ◦Have your own waste container ◦Rinse ◦5 -10ML ◦Pour Rinsing contents into waste container (250 mL Beaker)AT YOUR DESK

Instructions All work is done on station not in sink Careful ◦Bubbles ◦Volume Reading :Top to Bottom ◦Always have the waste container while setting up burette ◦Fill burette and start at integer value

Instructions Oxalic Acid ◦10 mL Pipette ◦Suck using bulb ◦Cap with finger and release to line ◦Empty into container ◦TD = To Deliver vs. TC = To Contain ◦Place Liquid Into 125 mL Erlenmeyer ◦Specifically Designed ◦Titration and Swirling

Instructions Oxalic Acid ◦10 mL in graduate cylinder ◦USE Erlenmeyer flask Will The Color Disappear? ◦6-8 hours to complete So How Do Speed Up The Reaction? ◦Heat? ◦Help Only Slightly ◦H 2 C 2 O 4 decomposes at 50 O C ◦Catalyst!

Catalysts What is it? ◦Increase RXN rate ◦Regenerated ◦Creates Proper Orientation H 2 SO 4 ◦THIS IS CONCENTRATED AND DOES NOT LEAVE THE CENTER DESK ◦After about 1 mL added, swirl and color should disappear

Lab Report Formulas ◦M = mol/L ◦Manipulation Calculations write down the molarities of each solution then ◦Calculate the volume used Initial – final reading ◦Calculate the moles of each solution ◦Need to end up with a whole number for each reagent in moles ◦Multiply by a big number equally, Round numbers, but beware of 0.5’s

Comments Molarity = Moles/ Volume // M 1 V 1 =M 2 V 2 Only account for displacement Might feel an increase in heat ◦Vapor ◦Endo- or Exothermic?

Sample Calculations M KMnO4 * 0.03 L = mole 0.05 M H2C2O4 * L = mole Round off to whole numbers and balance the equation watch the.5 values

Repeat 3 times Known [KMnO 4 ] mol/L mol/L mol/L [H 2 C 2 O 4 ] mol/L mol/L mol/L Vol. H 2 C 2 OmL mL mL Experimental Burette Reading (i)mL mLmL Burette Reading (f) mLmLmL Cacualtions Vol KMnO 4 (L) = LLL mols KMnO 4 = mol mol mol mols H 2 C 2 O 4 = mol mol mol Ave KMnO4mol Avearge Oxalic acid mol __KMnO 4 + __H 2 C 2 O 4 + __H + → Mn 2+ + CO 2 + H 2 O+ K + +O - + H +