
Betty asks…
Can you help me answer any of these chemistry questions?
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?

admin answers:
Wowzers sorry ur on ur own

Mary asks…
“Scientific honesty among cartel sponsored investigative groups is a myth…”……………………………
“…All medical schools, teaching universities, and government health organizations such as the National Institute of Health (NIH), National Cancer Institute, National Academy of Science, etc., etc. are all under the cartel’s propaganda umbrella.”
How do you explain this…?
Source:
Educate Yourself
– Forbidden Cures
– - Oxygen Therapies
– - – Hydrogen Peroxide
> – - – Medical Cartel Sponsered Studies
http://educate-yourself.org/fc/
Singlet Oxygen Therapies
– Hydrogen Peroxide
> – Medical Cartel Sponsered Studies
http://educate-yourself.org/fc/#singlet

admin answers:
“Vested interests”. That’s how I answer it. Each time I read a drug trial, I read the last line first… Who ‘sponsored’ the study and what are the ‘disclosures’ that the investigators make. I then know, generally without even having begun reading the trial, what the results are goint to be like. Times are strange, but its a reality.
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