11/20/2020Ch. 2 Exercises - Chemistry: Atoms First 2e | OpenStax1/102.1Early Ideas in Atomic Theory1. In the following drawing, the green spheres represent atoms of a certain element. The purple spheresrepresent atoms of another element. If the spheres of different elements touch, they are part of a singleunit of a compound. The following chemical change represented by these spheres may violate one ofthe ideas of Dalton’s atomic theory. Which one?2. Which postulate of Dalton’s theory is consistent with the following observation concerning theweights of reactants and products? When 100 grams of solid calcium carbonate is heated, 44 grams ofcarbon dioxide and 56 grams of calcium oxide are produced.3. Identify the postulate of Dalton’s theory that is violated by the following observations: 59.95% of onesample of titanium dioxide is titanium; 60.10% of a different sample of titanium dioxide is titanium.4. Samples of compound X, Y, and Z are analyzed, with results shown here.CompoundDescriptionMass ofCarbonMass ofHydrogenXclear, colorless, liquid with strongodor1.776 g0.148 gYclear, colorless, liquid with strongodor1.974 g0.329 gZclear, colorless, liquid with strongodor7.812 g0.651 gDo these data provide example(s) of the law of definite proportions, the law of multiple proportions,neither, or both? What do these data tell you about compounds X, Y, and Z?2.2Evolution of Atomic Theory5. The existence of isotopes violates one of the original ideas of Dalton’s atomic theory. Which one?6. How are electrons and protons similar? How are they different?7. How are protons and neutrons similar? How are they different?8. Predict and test the behavior ofαparticles fired at a “plum pudding” model atom.(a) Predict the paths taken byαparticles that are fired at atoms with a Thomson’s plum pudding modelstructure. Explain why you expect theαparticles to take these paths.
11/20/2020Ch. 2 Exercises - Chemistry: Atoms First 2e | OpenStax2/10(b) Ifαparticles of higher energy than those in (a) are fired at plum pudding atoms, predict how theirpaths will differ from the lower-energyαparticle paths. Explain your reasoning.(c) Now test your predictions from (a) and (b). Open theRutherford Scattering simulationand select the“Plum Pudding Atom” tab. Set “Alpha Particles Energy” to “min,” and select “show traces.” Click onthe gun to start firingαparticles. Does this match your prediction from (a)? If not, explain why the actualpath would be that shown in the simulation. Hit the pause button, or “Reset All.” Set “Alpha ParticlesEnergy” to “max,” and start firingαparticles. Does this match your prediction from (b)? If not, explainthe effect of increased energy on the actual paths as shown in the simulation.