Chemistry SM-1131 Week 1 Lesson 1 Chapter 9 Dr. Jesse Reich Assistant Professor of Chemistry Massachusetts Maritime Academy Fall 2008

Class Today Poem Test Review Finish the Timeline Lecture Electron Configuration One more exam the week of Dec 8 No class Friday

Quote “Go Big or Go Home”

Test Test was “bimodal” A good chunk of you guys got ridiculous As A good chunk of you guys haven’t learned a thing There wasn’t too much in between.

Test Review Q1: Aluminum sulfate and sodium phosphate double displacement rxn. Al 2 (SO 4 ) 3 + Na 3 PO 4  AlPO 4 + Na 2 SO 4 Al 2 (SO 4 ) 3 + 2Na 3 PO 4  2AlPO 4 + 3Na 2 SO 4 Al 2 (SO 4 ) 3 (aq) + 2Na 3 PO 4 (aq)  2AlPO 4 (s) + 3Na 2 SO 4 (aq) 2Al + 3 SO Na + 2 PO 4  2AlPO 4 +6 Na + 3SO 4 2 Al + 2 PO 4  2AlPO 4

Test Review Q2: 3 FeCl 2 + 2Al  2 AlCl Fe a.Single Displacement b.20.2g FeCl 2 x 1 mole FeCl 2 2 AlCl 3 132g AlCl 3 127g FeCl 2 3 FeCl 2 1 mole AlCl 3 = 14.1g AlCl 3 c. 300g Fe x 1 mole Fe x 2 mol Al x 27g Al 56g Fe 3 mol Fe 1 mol Al = 96.4g Al

Test Review 2d: Percent Yield = 100 X actual / theoretical Percent = 50% Actual = X Theoretical = % = x/ x 300 = x 150 = x 150g of Fe

Test Review Q3: C 2 H 6 + O 2  H 2 O + CO 2 2C 2 H O 2  4 CO H 2 O 26g C 2 H 6 x 1 mol C 2 H 6 x 7 mol O 2 x 32g O 2 30g C 2 H 6 2 mol C 2 H 6 1 mol O 2 = 97g O 2 … therefore 97g O 2 would be required, but I only have 26g so O 2 is the limiting reagent.

Test Review Q3: C 2 H 6 + O 2  H 2 O + CO 2 2C 2 H O 2  4 CO H 2 O 26g C 2 H 6 x 1 mol C 2 H 6 x 4 mol CO 2 30g C 2 H 6 2 mol C 2 H 6 = 1.73 mol CO 2 26g O 2 x 1 mol O 2 x 4 mol CO 2 32g O 2 7 mol O 2 = 0.46 mol CO 2 This must be limiting!

Test Review Q4: A: Decomp B: Combination C: Combustion D: Single Displacement E: Double Displacement

Test Review Q5: CH 4 + 2O 2  CO 2 + 2H 2 O 6 moles O 2 x 1 mol CO 2 2 mol O 2 = 3 mol CO mol H 2 O x 1 mol CH 4 x 16 CH 4 2 mol H 2 O 1 mol CH 4 = 188g CH 4

Test Review Q5: CH 4 + 2O 2  CO 2 + 2H 2 O 20g CH 4 x 1 mol CH 4 x 2 mol O 2 16 g CH 4 1 mol CH 4 = 2.5 mol O 2

Test Review Q6: Li 2 SO4 + CaCl 2  CaSO LiCl Li 2 SO 4 (aq) + CaCl 2 (aq)  CaSO 4 (s) + 2 LiCl (aq) 2Li + SO 4 + Ca + 2Cl  CaSO Li + 2 Cl Ca + SO 4  CaSO 4

Timeline

A Nagging Concern Rutherford’s Model Positive Protons and Oppositely Charged Electrons What should happen? Collapse!

Niels Bohr Oct. 7, 1885, Denmark – Nov. 18,

This is the quantized idea! He’s basically saying it can’t just be anywhere. It has to be in a specific space! Quantum means specific amount of energy, so not all energies are allowed, only certain ones. In this case it means that the electron has to stay a certain distance from the nucleus at all times… it’s not like standard physics.

A problem in physics: Spectrum of Hydrogen

A colorful spectrum of hydrogen

Bohr’s Idea What if the path of the electrons was fixed…

What energies would exist? What would that mean we would see?

A story of what would happen

A colorful spectrum of hydrogen

This is what he thought it would look like!

This model describes small atoms But……… When they looked at bigger atoms then hydrogen the model didn’t predict the light patterns accurately. Something was wrong with the model.

Erwin Schrodinger and Werner Heisenberg

Let’s talk about light, Baby!

What if it’s a particle?

1 Photon leads to 1 electron

Let’s talk about light, Baby!

But light moves in waves

Double Slit KinderUni2005/waves.gif

Here’s the experiment

Light or Wave? It’s both. It’s called the “wave particle duality.” Light sometimes acts like a particle and sometimes acts like a wave. It moves like a wave! Sometimes it hits like a particle.

Heisenberg Uncertainty This uncertainty leads to some strange effects. For example, in a Quantum Mechanical world, I cannot predict where a particle will be with 100 % certainty. I can only speak in terms of probabilities. For example, I can only say that an atom will be at some location with a 99 % probability, and that there will be a 1 % probability it will be somewhere else

Probability Density An abstract function, called wave function or probability amplitude (formula sign Y), describes the states of a particle or a physical system. Y is dependent on position and time. The wave function itself does not have any explicit meaning, but its square (more precisely the square of its absolute value) describes the probability of measuring the various possible positions of a particle. In addition, it provides information about the probability distribution of all other physical quantities (for example impulse and energy). Y satisfies the Schrödinger Equation, whose solution describes the behavior over time of a physical system. Schrödinger’s original formulation for particles with a given total energy E is as follows:

A compilation of individual electrons In 1927 Heisenberg formulated an idea, which agreed with tests, that no experiment can measure the position and momentum of a quantum particle simultaneously. Scientists call this the "Heisenberg uncertainty principle." This implies that as one measures the certainty of the position of a particle, the uncertainty in the momentum gets correspondingly larger. Or, with an accurate momentum measurement, the knowledge about the particle's position gets correspondingly less. The visual concept of the atom now appeared as an electron "cloud" which surrounds a nucleus. The cloud consists of a probability distribution map which determines the most probable location of an electron. For example, if one could take a snap-shot of the location of the electron at different times and then superimpose all of the shots into one photo, then it might look something like the view at the top.

This is what the probability density looks like for the first orbits described

James Chadwick Oct. 20, 1891, England – July 24,

Chadwick’s Setup In 1930, the German physicists Walther Bothe and Herbert Becker noticed something odd. When they shot alpha rays at beryllium (atomic number 4) the beryllium emitted a neutral radiation that could penetrate 200 millimeters of lead. In contrast, it takes less than one millimeter of lead to stop a proton. Bothe and Becker assumed the neutral radiation was high-energy gamma rays. Marie Curie's daughter, Irene Joliot-Curie, and Irene's husband, Frederic, put a block of paraffin wax in front of the beryllium rays. They observed high-speed protons coming from the paraffin. They knew that gamma rays could eject electrons from metals. They thought the same thing was happening to the protons in the paraffin. Chadwick said the radiation could not be gamma rays. To eject protons at such a high velocity, the rays must have an energy of 50 million electron volts. The alpha particles colliding with beryllium nuclei could produce only 14 million electron volts. Chadwick had another explanation for the beryllium rays. He thought they were neutrons. He set up an experiment to test his hypothesis.

Chadwick’s Experiment Chadwick collided the radiation emerging from the (Po-Be) source not only with proton (paraffin), but also with helium and nitrogen. Comparing the results of these experiments with each other, Chadwick concluded that this mysterious radiation from the (Po-Be) source cannot be interpreted by assuming it to be a gamma ray. He finally concluded that all were able to be understood without any contradiction by assuming that the mysterious radiation is electrically neutral particles with almost the same mass as a proton. This is the confirmation of the existence of the "neutral proton" predicted by Rutherford. Chadwick named this particle "neutron" (1932). www2.kutl.kyushu-u.ac.jp

In his own words The properties of the penetrating radiation emitted from beryllium (and boron) when bombarded by the a-particles of polonium, have been examined. It is concluded that the radiation consists, not of quanta as hitherto supposed, but of neutrons, particles of mass 1, and charge 0. Evidence is given to show that the mass of the neutron is probably between 1·005 and 1·008.