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From Omilili

Direction of molecular dipole moment

Wondering if I can characterize the angle between the dipole moment and long molecular axis. By the way moment vector and determine the angle between it and the molecular axis. However, many your molecule is large, I would suggest optimizing the geometry with a low level of theory and small

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Question:I have 2 AP Chem questions that i'm stuck on: 1.) Which member will have the HIGHER VAPOR PRESSURE at 25 degrees C: Water (H2O) or Propanol (C3H7OH)? -I know the answer is Propanol b/c I looked up the Boiling points and Propanol has a Lower BP. But I dunno why?? 2) Bromoethane (CH3CH2Br) is slighly miscible in water while Acetone CH3CCH3 is completely miscible in water. Why?? O In Acetone the O is dub.bonded to the C.

Answers:Both of these questions deals with intermolecular forces (dipole-dipole, induce dipole - dipole ect.) on the molecules in question. 1) Water has a lower vapor pressure because it has stronger intermolecular force then propanol. It takes more energy to break the hydrogen bonds of water then the hydrogen bonds/ induce dipole-induce dipole bonds of propanol. General rule of thumb when comparing two molecules with hydrogen bonding is, the more non polar substituents it has attach (usually organic stuff) the weaker the intermolecular forces are. Larger dipole moment equates to lower vapor pressure. But with induce dipole induce dipole (no relatively highly electronegative atom present in the molecule like alkanes) it is opposite, larger molecules have higher boiling points. 2. To be miscible in a solvent, the dipole moments of the two substances have to be similar. Bromoethen has an electron withdrawing group to create a dipole but it is not as strong of a dipole as oxygen can create. The dipole moments of acetone and water is much more similar then bromoethane and water. Entropy (going from order to disorder) drives miscibility of a substance but at the same time you have to keep in mind the intermolecular forces of the two substances. The bonds of water to water and acetone to acetone have to break and water to acetone have to form. If the difference in energy is too large then the substance will not mix, if they are close then they will mix. Gibb's free energy equation explains this ((delta)G = (delta)H - T(delta)S). If enthalpy is huge and positive (the breaking and forming bonds) this will over ride the entropy term, if enthalpy is small and positive or maybe even slightly negative then enthalpy will drive the two substances to mix. Gibb's free energy also can be use for the first question too. The weaker the intermolecular forces of the substance, the more driving the force of entropy to turn into gas (more disorder then liquid). If the intermolecular forces are strong and therefore there is a large and positive enthalpy, the less likely the entropy will drive the phase change forward at lower temperatures.

Question:The person who can answer the most questions gets best answer. Only the first person who answers the queston can get points for it. 1. Lithium consists primarily of two isotopes with mass numbers 6 and 7, respectively. Write the nuclear symbols for each of these isotopes. Given the average atomic molar mass of lithium (see periodic table). which of the lithium isotopes predominates in nature? Explain. 2. Gold-198 is a beta producer with a half-life of 2.7 days that has been used as an implant for cancer therapy. For an implant containing 50 g of Au-198, approximately how much Au-198 remains after 1 week? 3. Explain what it means for an atom to be in an excited state and what it means for an atom to be in its ground state. How does an excited atom return to its ground state? What is a photon? How is the wavelength (color) of light related to the energy of the photons being emitted by an atom? How is the energy of the photons being emitted by an atom related to the energy changes taking place within the atom? 4. Do atoms in excited states emit radiation randomly, at any wavelength? Why? What does it mean to say that the hydrogen atom has only certain discrete energy levels available? How do we know this? What does it mean to say that the energy levels of an atom are quantized? 5. What do the principal energy levels and their sublevels represent for a hydrogen atom? How do we designate specific principal energy levels and sublevels in hydrogen? Describe the sublevels and orbitals that constitute the second principal energy level of hydrogen. How are the individual orbitals in these sublevels designated? 6. List the order in which the orbitals are filled as the atoms beyond hydrogen are built up. How many electrons overall can be accommodated in the first and second principal energy levels? How many electrons can be placed in a given s subshell? In a given p subshell? In a specific p orbital? Why do we assign unpaired electrons in the 2p orbitals of carbon, nitrogen and oxygen? 7. Define the valence electrons in an atom. Define the core electrons in an atom. Why are the valence electrons more important to the atom's chemical properties than the core electrons? How is the number of valence electrons in an atom related to the atom's position on the periodic table? What evidence convinces us that the 4s subshell fills before the 3d subshell? 8. What bond angle results when there are only two valence electron pairs around an atom? What bond angle results when there are three valence pairs? What bond angle results when there are four pairs of valence electrons around the central atom in a molecule? Give examples of molecules containing these bond angles. 9. How do we predict the geometric structure of a molecule whose Lewis structure indicates that the molecule contains a double or triple bond? Give an example of such a molecule, write its Lewis structure, and show how the geometric shape is derived. 10. Write Lewis electron structures for each of the following molecules or ions, and use the VSEPR theory to predict their geometric shapes. If resonance is possible for any of the molecules or ions, draw all likely resonance structures. a. GeC4 b. NO3 c. SO4-2 d. SO3-2 e. SO2 f. O2 g. O3 h. CH3NH2 i. C2H6 j. C2H4 k. BF3 l. BeF2 m. NO2- n. PF3 o. N2H4 11. Describe some of the physical properties of water. Why is water one of the most important substances on earth? 12. Define the normal boiling point of water. Why does a sample of boiling water remain at the same temperature until all the water has been boiled? Define the normal freezing point of water. Sketch a representation of a heating/cooling curve for water, marking clearly the normal freezing and boiling points. 13. Are changes in state physical or chemical changes? Explain. What type of forces must be overcome to melt or vaporize a substance (are these forces intramolecular or intermolecular)? Define the molar heat of fusion and molar heat of vaporization. Why is the molar heat of vaporization of water so much larger than its molar heat of fusion? Why does the boiling point of a liquid vary with altitude? 14. What is a Dipole-dipole attraction? How do the strengths of dipole-dipole forces compare with the strengths of typical covalent bonds? What is hydrogen bonding? What conditions are necessary for hydrogen bonding to exist in a substance or mixture? What experimental evidence do we have for hydrogen bonding? 15. Define dispersion forces. Are London forces relatively strong or relatively weak? Explain. Although London forces exist among all molecules, for what type of molecule are they the only major intermolecular force? 16. Why does the process of vaporization require an input of energy? Why is it so important that water has a large heat of vaporization? Define the equilibrium vapor pressure of a liquid. Describe how this pressure arises in a closed container. How is the magnitude of a liquid's vapor pressure re 17. Define a crystalline solid. Describe in detail some important types of crystalline solids and name a substance that is an example of each type of solid. Explain how the particles are held together in each type of solid (the interparticle forces that exist). 18. Define a solution. Describe how an ionic solute such as NaCl dissolves in water to form a solution. How are the strong bonding forces in a crystal of ionic solute overcome? Why do the ions in a solution not attract each other so strongly as to reconstitute the ionic solute? How does a molecular solid such as sugar dissolve in water'? What forces between water molecules and the molecules of a molecular solid may help the solute dissolve? Why do some substances not dissolve in water at all? 19. Define a saturated solution. Does saturated mean the same thing as saying the solution is concentrated? Explain. Why does a solute dissolve only to a particular extent in water? How does formation of a saturated solution represent an equilibrium'? 20. A solution of 7.50 g of a nonvolatile compound in 22.0 g of water boils at 100.78oC. What is the molecular mass of the solute? 21. The freezing point of water is lowered to -0.390oC when 3.90 g of a nonvolatile molecular solute is dissolved in 475 g of water. Calculate the molar mass of the solute. 22. What is the freezing point of a solution of 12.0 g of carbon tetrachloride dissolved in 750 g of benzene? freezing point of benzene is 5.48oC, kb= 2.53oC.kg/mol. 23. What is the freezing point of these solutions? a. 1.40 mol of Na2SO4 in 1750 g of water b. 0.60 mol of MgSO4 in 1300 g of water 24. What is the molar mass of a compound if 4.80 g of the compound dissolved in 22.0 g of water gives a solution that freezes at -2.50oC? 25. What is the molality of a solution containing 100.0 g of C2H6O2 in 150 g of water? What is the boiling point of this solution? What is the freezing point of this solution?

Answers:wowzers sorry ur on ur own

Question:Why do the list of molecular polarities differ? Taking the liquids: 2-Propanol Water Acetone and placing them in order of increasing polarity using electronegativity we get: 2-propanol water acetone. But! If we use their physical properties, ex.: density, angle of deflection, flow rate, and boiling point we get: Acetone 2-Propanol water Why do the lists differ???

Answers:2propanol has an OH on the second, middle C for CH3CHOHCH3, this OH- sticks up from the middle but has a CH3 on either side decreasing the polarity of the molecule a bit. H2O is a bent molecule with polarity towards the 2 non-bonding pairs of electrons on oxygen acetone, like 2-propanol has the polarity pointing towards the 2 non-bonding pairs of electrons but, also like 2-propanol, has a CH3 on either side, decreasing the polarity some. for both acetone and 2-propanol, the "side" CH3 are much bigger and decrease the polarity of the molecule more than the "side" H on H2O. electronegativity is a measure of one element's ability to take an electron from another element. for 2-propanol, we are looking at the bond between C-O-H, not just C-O, electronegativity of C = 2.55, O = 3.44, H = 2.2. basing polarity on density, bp, etc. this is a measure of the intermolecular forces, such as H bonds, dipole-dipole moments, etc. water has very strong H bonds and will have a higher bp than the other 2 but if we compare this with electronegativity, an OH bond has the combined electronegativity of 2.48 while the COH bond has an electronegativity of 3.02 and the C=O bond in acetone 3.44.

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Backwards Videos- Pool and Valley Park

Me and a few of my friends experimenting and having fun. -----Tags Ignore----- Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water appears in nature in all three common states of matter and may take many different forms on Earth: water vapor and clouds in the sky; seawater and icebergs in the polar oceans; glaciers and rivers in the mountains; and the liquid in aquifers in the ground. The major chemical and physical properties of water are: Water is a tasteless, odorless liquid at standard temperature and pressure. The color of water and ice is, intrinsically, a very slight blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas.[10] Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly absorbed. Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, it carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an electrical dipole moment. The net interactions between the dipoles on each molecule cause an effective skin effect at the interface of water with other substances, or air at the surface, the latter given rise to water's high surface tension. This dipolar nature contributes ...

Dry Ice 3

Properties Crystal structure of dry iceFor supplementry chemical data, see Carbon dioxide (data page). Dry ice is the solid form of carbon dioxide (chemical formula: CO2), comprising two oxygen atoms bonded to a single carbon atom. It is colourless, odourless, non-flammable, and slightly acidic.[1] Carbon dioxide phase diagramCO2 changes from a solid to a gas at 78.5 C ( 109.3 F) with no intervening liquid form, through a process called sublimation. The opposite process is called deposition, where dry ice changes from the gas to solid phase. The density of dry ice varies, but usually ranges between about 1.4 and 1.6 g/cm3 (87100 lb/ft3).[2] The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water or ice and leaves no moisture as it changes state.[3] Its enthalpy of sublimation ( rH) is 393.5kJ/mol.[4] Dry ice is non-polar, with a dipole moment of zero, so attractive intermolecular van der Waals forces operate.[5] The composition results in low thermal and electrical conductivity.[6]

You Must Bond With Me (Organic Chemistry Music Video)

Learn! Laugh! and Share! =D This is a parody of Taylor Swift's "You Belong With Me". As an extra credit project for our organic chemistry course, we were required to write a song about organic chemistry. Here's what we came up with: Addition of X2 (halogens) Alkenes, polar solvents, tosylate and substitution. Makers: Will De Vega, Edith Gusan and Amy Tran You Must Bond with Me Lyrics Youre in a flask with your double bonds, youre all set To break some bonds and fill a new octet But you dont have anything to react to Im in a tube with my electrons and Im Bonded to one of my many look-a-likes You guessed it, I am one of those halogens Youve got pi bonds I get repulsive Here comes my not so strong dipole moment Put us together, well react and youll find that my Twin and I are on different sides (of you) Carbon chains with double bonds are alkenes Add me in and we can make a really good te-e-eam Just you and me. You must bond with me. Now, were in the same flask, let us deal Ill share my electrons with yours thats if you feel Like breaking your double bonds and forming two single bonds With someone like me, yeah And yet theres a catch whenever we meet up, The polar solvent wants to take a shot, In bonding with your positive charge, Does it even know the key to your heart? I broke your pi bond We form a cycle Youve got a charge and were still unstable Coming from behind is my negative twin, Who will take it away and save the day But the pesky polar solvent is still there ...

AP Chemistry: Covalent Bonds

www.mindbites.com Join Jonathan Bergmann and Aaron Sams, nationally known Chemistry teachers. This is one in a series of lessons that cover all the necessary topics in an Advanced Placement Chemistry Course. In this lesson you will learn about: a. Types of Bonding b. Electronegativity c. Bond Polarity d. Dipole Moments e. Electron configurations Also remember that you can buy the complete series by going to chempodcasts.com

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