2Synthesis of Zinc Chloride (single-replacement) A + B → AB Zn + 2HCl → ZnCl2 + H2 By Amparo Krug 2009
3Group Data Zn metal initial _________ g Zn metal final __________ g Empty dish __________ gDish with solid (ZnCl) ________ gTotal 38 points on grade book divide by 2, 19 points
4Calculations Mass of Zinc Reacted = B – A Mass of ZnCl produced = D – CRatio of mass of Zn reacted = ____mass of ZnCl produced
5Ratio (Zn reacted/ZnCl produced Class Data exampleZn reacted (g)ZnCl produced (g)Ratio (Zn reacted/ZnCl produced0.430.770.8126.96.36.1991.713.541.91.483.971.883.981.83.710.420.830.871.75
6Graph ZnCl produced vs. Zn reacted. Dependent Variable Independent Variable
7BDQ1 What is the gas given off in the reaction? The gas is hydrogen BDQ2 Why should you add the washing water to the evaporating dish? Because it contains some of the dissolved productBDQ3 How much of the metal reacted with the HCl? Mass Zn initial – mass of Zn remaining.
8BDQ4 What is the ratio of the mass of zinc reacted to the mass of zinc chloride formed? 0.48 BDQ5 Compare your results with those of your classmates. Did an excess of either zinc or hydrochloric acid affect your results? No an excess of either reactant did not affect the final ration.BDQ6 If the zinc chloride were not completely dry when massed, how would this affect your ratio? The mass of the product would be larger and the final ratio would therefore be smaller.
10ConclusionPurposeThe purpose of this experiment is to investigate what happens when a metal is dissolved in an acid.HypothesisMy hypothesis that the amount of Zinc that reacts with HCl will depend on the amount of Zn was partly supported.Group DataOur group data revealed that the mass ratio of Zn reacted to ZnCl produced was See group data in page 35.Class DataThe class also had an average mass ratio of See the group data in page 36.SummaryZinc and HCl will chemically combine in a constant proportion no matter the amounts of the reactants that is used.
11The graph shows a line with a positive slope which flattens at about 4 The graph shows a line with a positive slope which flattens at about 4.0 g of ZnCl produced and1.9g Zn reacted.There was enough HCl to react with 1.9g of ZnCl. Any additional Zn would go un-reacted because there is not enough HCl to react with.
12The limiting reactant in this part of the graph was Zinc. Groups with less than 1.9g of Zn did not have enough Zn to react with the ChlorineThe limiting reactant in this part of the graph was Zinc.ZnHClHClZnZnHClZnHClHClHClLeft over HCl
13The limiting reactant in these groups was HCl. Groups with greater than 1.9g Zn used up all their HCl and were evaporating water.The limiting reactant in these groups was HCl.ZnHClZnHClZnHClZnHClZnLeft over ZnZn
14Lab 6.6 Reaction with Copper By Amparo Krug2006POST LABThis lab will be done as a demo because we are running out of time.
15BDQBDQ 6.6.1: Does a reaction take place? Yes, because there was a color change.BDQ 6.6.2: Did the crucible and contents gain or lose mass? Gained mass
16BDQ 6.6.3: Is your answer to the previous question evidence that a reaction has taken place? Increase in mass is evidence that something was added to the copper.BDQ 6.6.4: What do you predict will happen if you continue to heat the crucible for an additional minutes? Accept any reasonable response.
17BDQ 6. 6. 5:. Do you think that all the copper has reacted BDQ 6.6.5: Do you think that all the copper has reacted? No, because there were flakes of copper in the solid. If not, what fraction do you estimate did not react? about 1/8 (accept any reasonable fraction)BDQ 6.7.1: What does the remaining solid look like? The solid remaining in test tube A looked like copper.BDQ 6.7.2: Is the black substance a mixture? Yes, because we were able to separated the unreacted copper by using solubility.BDQ 6.9.1: Can you identify the solid? It looks like copper.
18Conclusion (each purpose is address in one encompassing statement) The purpose of these labs was to determine if:6.6) The reaction of copper with oxygen goes to completion. Our lab group found that the reaction of copper with oxygen is incomplete producing a mixture.6.7) Can this mixture be separated and the un-reacted copper collected. Yes, we separated the un-reacted copper in the mixture.6.9) Can the Cu in the reacted CuO be isolated from the compound. Definitely, we precipitated the copper that was chemically combined with oxygen to make CuO.Theoretically, the mass of the copper in the two separations of the product equals the initial mass of the Copper used.
19Lab 6.6 2Cu (s) + O2 (g) > CuO +Cu A reaction has taken place because of the mass increase (something is added to the Cu) and color changed.CuO +Cu was a mixture and mixtures can be separated by physical means. Which method was used? Separation by solubility, dissolvingCuO will dissolve in HCl and Cu will not
20Lab 6.7 CuO +Cu + 2HCl > 2CuCl + H2O ↓ Un-reacted Copper stays behind in test tube ACuCl (green liquid) is now in test tube B
21Even though, copper reacted with air to produce a compound, subjected to heat and acid, we still were able to recover the copper. The properties of the copper had not changed.A substance that can keep its identity through all these processes can be called an Element.
22Lab 6.9 ↓ Copper is filtered out 2CuCl (green) + Zn + H2O > ZnCl2 (dissolves in water and becomes clear) + 2Cu + H2O↓Copper is filtered outYou know that a reaction has taken place because of the color change, formation of precipitate, and release of energy (exothermic). The product has a different identity than the reactant.
23MixtureIs a combination of different substances that can be separated because they have different physical properties – such as boiling point, melting point, density.The substances are not chemically bonded.
24Pure substance Pure substance Concept mapConcept MapMixturePure substance Pure substanceCompound ElementPure substance ElementCompound ElementSeparate intoCan beCan beorBroken into
25Mixtures can be separated by physical means into pure substance. A pure substance can be a compound or an element
26CompoundsCannot be separated by physical means, because they are chemically bonded.Have different properties from the elements of which they are made.Are synthesize from other pure substances in constant ( definite ) proportions.Can be written as a chemical formula which shows the proportion of the elements in the compound.
27Elements:Are pure substances made up of atoms of the same type, all with the same atomic number.Cannot be broken down by electrolysis, reacting with acid, nor heating to form simpler substances.
28In summary Compounds can be separated into other compounds or elements But Elements cannot be subdivided.
29Famous Scientist who helped separated compounds into elements.
30ANTOINE LAURENT LAVOISIER, 1743-1794 Discovered iron, copper, silver, gold, hydrogen, oxygen, and carbon.Discovered the true nature of burningChemical addition of oxygenIntroduced quantitative analysisHelp invent the metric systemFather of modern chemistry
31Alessandro Voltainvents the battery, 1800, which helped chemist separate pure substances into other pure substances (elements and compounds)
32Sir Humphry Davy, – 1829English chemist using electrolysis decomposes Potash into potassium and sodium in 1807.Isolates calcium from Lime (as in limestone)in 1808.Isolates strontium, barium and magnesium in 1808.Davy isolates the new gas from his experiments with muriatic acid and names it chlorine because of its’ green color.Discovered the anesthetic action of nitrous oxide.Lime has been known since 200 BC as a pure substance.
33Elements Near the Surface of the Earth (top 8) OxygenSiliconHydrogenAluminumIronCalciumSodiumMagnesiumThe first 5 form 92% of the total mass of the elements found near the surface of the earth.
34Silicates Oxygen and silicon form silicon dioxide. Silicon dioxide is the compound found in rock forming minerals.
35Ores are materials found in the ground from which metals can be profitably extracted. Iron is produced by mixing iron ore with coal or charcoal and heated stronglyAluminum comes from Bauxite –aluminum ore