Tutor profile: Carl C.
Subject: Nuclear Physics
The binding energy per nucleon for Co-60, calculated from the liquid drop model, in MeV, is closest to?
Knowing A=60 and Z=27, Use the semi-empirical mass formula. Where the coefficients are: a(V)=15.85MeV, a(S)=18.34 MeV, a(A)=23.21 MeV, a(C)=0.714 MeV, a(P)=12.00 MeV, and delta(o)=a(P)*A^(-1/2) In this case since the number of protons is odd, the pairing term becomes zero (delta(o))=0. The approximate binding energy using the SEMF is Eb=523.04MeV, the energy per nucleon is just Eb/A or 523.04/60=8.717 MeV.
Subject: Basic Chemistry
Given a molecule of water (H2O), what is the electron-pair geometry and molecular geometry of the molecule. Also, state the bond angle in degrees.
Applying the VSEPR theory to the electrons and utilizing the shorthand "AXE method" of electron counting, we count there are 2 bonded atoms (Hydrogen) to the central atom (Oxygen). Knowing that Oxygen has 6 valance shell electrons and 1 will be used for each bond with each hydrogen atom, that leaves a total of 4 valance electrons floating around the oxygen atom (or two lone pairs). The AXE method gives H2O a notation of AX(2)E(2). With this notation we can look up the Electron and Molecular geometries. The electron geometry is that of a tetrahedral, while the molecular geometry is that of a bent structure. The approximate interaction between the two hydrogen atoms and the two lone pairs give rise to a bond angle of 109.5 degrees or in some literature 104.48 degrees.
Subject: Chemical Engineering
List and briefly define the three types of heat transfer and give an example of each.
Convection-Movement of matter due to differences in density that are caused by temperature gradients Ex. Hot air transferring to a colder environment Conduction-Transfer of heat between atoms as they collide within a substance. Ex. Heating of a metal plate Radiation-Transfer of energy by EM waves Ex. Sunlight transferring heat to earth
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