How should we analyze our data?

How should we analyze our data? • Get together in your groups and discuss/Do Calculations.. • Determine Error that may have effected results and how it affected results. • What might you change next time in your lab? • What type of calculations do we need? • Calculations that show how you determined the amount of reactants needed to create 5.00g of product • Calculations that show how precise our data was • Ex: % Error, % Yield (Formula on Handout)

What background information would our reader need? • Reaction Types to predict products • Solubility Rules • Balancing Equations • How you were able to determine the amount of reactants….Stoichiometry…..

Mole Relationships • One mole of atoms, ions, or molecules contains Avogadro’s number of those particles • One mole of molecules or formula units contains Avogadro’s number times the number of atoms or ions of each element in the compound

Stoichiometric Calculations The coefficients in the balanced equation give the ratio of moles of reactants and products

Stoichiometric Calculations From the mass of Substance A you can use the ratio of the coefficients of A and B to calculate the mass of Substance B formed (if it’s a product) or used (if it’s a reactant)

Stoichiometric Calculations C6H12O6 + 6 O2 6 CO2 + 6 H2O Starting with 1.00 g of C6H12O6… we calculate the moles of C6H12O6… use the coefficients to find the moles of H2O… and then turn the moles of water to grams

Lets recap for the Lab Report

Remember that this is just one system of typing chemical reactions. There are other ways of organizing them, with different names, such as: • Oxidation-reduction (Redox) occurs when electrons are exchanged in a reaction. All single replacement, synthesis,decomposition and combustion reactions involve electron exchange • Acid-Base (a type of double replacement) occurs when an acid (containing hydrogen ions) reacts with a base (containing hydroxide ions) to produce a salt and water

Oxidation-Reduction Ca(s) + S(s)  CaS(s) = Synthesis What is happening at the atomic level? Calcium is losing two electrons to sulfur. In the process, calcium becomes 2+ ion, and sulfur becomes a 2- ion. They are attracted and bond ionically.

Another example: Aluminum metal replaces copper metal in a solution of copper(II) chloride. Al(s) + CuCl2(aq)  AlCl3(aq) + Cu(s) = single replacement reaction. Al & Cu trade places. They do so by transferring electrons. Al loses three electrons Al  Al3+ + 3 e- Copper gains two electrons 2 e- + Cu2+  Cu

Acid-Base Reaction HX(aq) + YOH(aq)  YX(aq) + H2O(l) Ex. HNO3(aq) + KOH(aq)  KNO3(aq) + H2O(l) Net ionic equations are always the same. H+(aq) + OH-(aq)  H2O(l)

Oxidation Reduction • Like LEO the Lion goes GER • Gain Electrons Reduction • Loose Electrons Oxidation

Oxidation Reduction Problems • Mg + HCl > MgCl2 + H2 • What is being oxidized? Reduced? • Charges they start with • Mg 0 H +1 Cl -1 • Charges they end with Mg+2 Cl -1 H 0 Mg oxidized:Mg 0 - 2e- => Mg +2 • H reduced H+1 + 1e- => H 0

Try this one… • 2K + F2 > 2KF • What is oxidized? Reduced • Starting Charge K,0 F,0 • Ending Charges K+, F- • F GER… Reduced K LEO Oxidized

How about this one.. • 2Fe(s) + 3S(s) > Fe2S3 • Original Charges Fe 0, S,0 • Ending Charges Fe 3+ S 2- • S GER… 0>2- Reduced • Fe LEO…. 0> 3+ Oxidized

How should we analyze our data?