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  1. Q

    Normal Stress in Rods Experiencing Temperature Changes

    Now here is the part where I'm sort of stumped myself: Could someone let me know if my reasoning is valid? The professor explained it during office hours and all I got out of that was that something cancels out and the answer is 0.
  2. Q

    Proper free-body diagram for a shaft experiencing multiple torques

    I wish to draw a proper free-body diagram for this shaft. However, my FBD does not agree with the solutions manual. If someone could point out where I erred, that would be great. This is what I drew: From my FBD, it is clear that the maximum torque is present in section DE of the shaft. We...
  3. Q

    Finding the maximum height of a projectile

    Using the equations for constant acceleration, we can write the following set of equations for this problem: We have the following known physical constraints: Solving the above system of equations and constraints with a computer algebra system: So, all the solutions I found make...
  4. Q

    Finding the final y-position of a projectile

    Summary:: After firing a projectile from the top of a hill, where does it land on the hill? I disagree with the professor in approach and final result. Problem Statement: Relevant Formulas: Attempt to Solve: I'm very familiar with these types of problems. I'm not here for help solving...
  5. Q

    Engineering Should one include friction in this free-body diagram?

    Problem statement: Attempt at a solution: 1) There are no relevant moments that need to be drawn in this free-body diagram. 2) There is tension in the chain DE that is pointed away from the truck, i.e. from D to E. 3) There are "ground" reaction forces at points A and B pointed up toward...
  6. Q

    Converting source intensity to the maximum reach of beam flux

    We can solve for the maximum 5 lux illumination distance with the above equation. E = 10.76*(35,000/d^2) d = 275 feet (approximately). However, the 5 lux illumination distance is not 275 feet. The 35,000 cd value is not an axial intensity value. It is at a point that is slightly down and to...
  7. Q

    Electropositivity - 2nd opinion needed

    Homework Statement I have a significant problem with the following excerpt from a general chemistry text: Note that ON stands for oxidation number (state). The excerpt is with regard to polyatomic anions - specifically, chloride ion and its related polyatomic anions. >It now follows that as...
  8. Q

    Diels-Alder - Explanation?

    Homework Statement This is my prof's explanation of Diels-Alder ... below is the mechanism and some resonance structures he drew to explain the concerted movement of electrons to the class ... Homework Equations Nucleophiles attack electrophiles. Electrons in HOMOs go into LUMOs. The...
  9. Q

    Stability of Sulfides

    Homework Statement The attempt at a solution 1) Is the above excerpt describing pi-backbonding? It seems to be describing some form of backbonding because the electron density is moving away from the positively charged metal cation (rather unexpected based on superficial Columbic analysis)...
  10. Q

    Mechanism of saponification

    Homework Statement Problem: I am told that the first mechanism is operative in saponification. The Attempt at a Solution However, this strikes me as wrong because the first mechanism involves the formation of dianion. Using hydroxide ion to abstract a proton and make that particular...
  11. Q

    Steric Effects on Basicity

    Homework Statement How do sterics affect basicity? Homework Equations Sterics has to do with kinetics. Basicity is a thermodynamic property. Nucleophilicity is a kinetic property. The Attempt at a Solution So is the answer "sterics don't affect basicity"? I can't see why sterics...
  12. Q

    PH dependence of reduction of oxygen

    Homework Statement Why is this true? Why is it that the reduction of oxygen is more favored in acidic solution rather than in basic solution? Homework Equations Acids are proton donors. The Attempt at a Solution Does this have anything to do with the fact that the...
  13. Q

    Polarity of the Binary Halogen Acids

    Does the polarity of the binary halogen acids increase or decrease down the group? I have one argument for decrease based solely on electronegativity considerations. I have one argument for increase based on orbital overlap and electron density. Taking electron density in an orbital to be...
  14. Q

    Naming of Haloalkane (Disputed)

    My teacher insists the name of this compound is (2S)-chloro-3-methyl-3-propylhexane Shouldn't it be 4-(1-chloroethyl)-4-methylheptane? (Ignore R,S configuration for now). Chemoffice also tells me 4-(1-chloroethyl)-4-methylheptane. I think it's the latter because I've consulted three...
  15. Q

    Nomenclature - IUPAC and Common Names

    Homework Statement What if we stuck with the IUPAC name and called the isopropyl group a 1-methylethyl group? That would definitely reverse the alphabetical priorities; because the substituents here on the hydrocarbon are on equivalent positions, we must give the lower number to the...
  16. Q

    Lewis Acid/Base Chemistry in formation of Sulfuric Acid

    Homework Statement How does sulfur trioxide react with water to form sulfuric acid Homework Equations This is clearly a Lewis acid/base problem. The Attempt at a Solution Okay, I tried drawing sulfur trioxide out with three double bonds (as it is traditionally drawn). I know...
  17. Q

    Most Exothermic Combustion of Hydrocarbon

    Homework Statement Which would have the most negative heat of combustion? Consider only the best conformer. cis-1,3-dimethylcyclohexane trans-1,4-dimethylcyclohexane Homework Equations The more negative the heat of combustion, the more exothermic the combustion. We are...
  18. Q

    Figuring out Primary/Secondary/Tertiary Structures

    Homework Statement In general, when presented with a problem such as write out all the primary alcohols/amines/ketones/aldehydes with this formula ________, how do I actually go about systematically figuring them out? I have seen problems with up to 8 different structures for me to figure...
  19. Q

    Formula Writing

    What are your thoughts on this excerpt from my chem prof's textbook? I have a few problems with the beginning of the text and a huge problem with the bolded statement. I understand the intentions of my teacher - structure - is highly important in chemistry. Not so much emphasized in general...
  20. Q

    Electrophilic nature of Carbon in CO2

    How is the carbon in carbon dioxide electrophilic? There is no partial positive charge on the carbon in carbon dioxide because the molecule is symmetrical.
  21. Q

    The Acidity of the Hydrated Ferric Ion

    Why is Fe(OH_{2})_{6}^{3+} fairly acidic? This iron has six water molecules coordinated to it. In other words, water itself is a very weak acid. But when water is coordinated to iron, it becomes more acidic. I can think of a few reasons; can you think of more? 1) Induction. The negative charge...
  22. Q

    Would this be a picture of pentene?

    Homework Statement Would this be a picture of pentene? I'm unsure because of the location of the double bond - does the location of the double bond factor into naming alkenes?
  23. Q

    Chair Conformations of Cyclohexane - equivalent structures?

    Homework Statement Are these structures equivalent? Here's the professor's rendering: [Broken] The Attempt at a Solution Here's my rendering. The molecule is 1-chloro-2-ethylcyclohexane. I had projected the chlorine out of the page and the...
  24. Q

    Tetrahedron; Sum of Bond Angles

    Homework Statement Prove that if bonding-pair repulsions were maximized in CH3X, then the sum of the bond angles would be 450°. Homework Equations In a perfect tetrahedral molecule (e.g. methane), the sum of the bond angles is about 438 degrees (109.5° times 4). The Attempt at a...
  25. Q

    Statements about Resonance

    Homework Statement Are the following statements true? 1) All contributing resonance structures must have the same net formal charge. 2) All atoms in contributing resonance structures must have complete octets. The Attempt at a Solution The first one strikes me as true. Net formal...
  26. Q

    Electric field strength goes to 0

    Homework Statement Two point charges lie on the x-axis. Charge Q1= +7 μC is located at x = 0 and charge Q2 = -18μC is located at x = 25 cm. Find the point on the x axis (in cm) where the net electric field is zero. Homework Equations E = F/C F = k(q1)(q2)/r^2 The Attempt at a...
  27. Q

    Fluid Mechanics and hydraulic lever

    Homework Statement In a hydraulic lever consisting of two ideal fluid lined cylinder/pistons with a fluid filled line coupling the two cylinders, the output force is 100 times the input force. For 1 Joule of work done on the input side, the work done on the output side is (in J)...
  28. Q

    Resonance structures for nitric oxide

    Homework Statement Is N triple bond O with a radical on oxygen a valid LS for the nitric oxide molecule? Homework Equations Max number of valence electrons in a shell - 2n2. Oxygen is in second row of periodic table. Max valence electrons: 2(2)2 = 8. The Attempt at a Solution I...
  29. Q

    1-chloro-3-methylcyclobutane - IUPAC name

    Homework Statement Name this molecule Homework Equations Naming cycloalkanes: 1) The functional groups should receive the lowest carbon number. 2) Any substituents are then assigned carbon numbers. The Attempt at a Solution Following the above two rules, shouldn't the molecule...
  30. Q

    Hybridization and Hypervalent molecules

    Are species such as sulfuric acid and phosphoric acid better represented as charge-separated species rather than as species with no formal charge on any of the constituent atoms? Also are the central atoms of trigonal bipyramidal molecules (e.g. phosphorous) hybridized as sp3d2 or do such...