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  1. D

    Hardest SNAr Regioselectivity Prediction

    During one of my internship in a big pharma in San Francisco, I had to prepare a new core by SNAr on a tetrahalopyrimidine. Link to Reddit post Predicting the regioselectivity of the second SNAr may seem obvious to an experienced eye, but take your time and explain. Will the substitution occur...
  2. P

    Chemistry unit lab problem

    Hi everyone, Wondering if someone could help me with this lab problem. I can't get my head around it. NaOH= 40,00g/mol p = 2,10 g/cm3 I want 100 ml aq with 0,400 mol/kg How do I solve this? Thanks in advance:)
  3. C

    Stoichiometry Problem

    f you reacted 1 mol of aluminum (Al) with 1 mol of iodine gas (I2), what amount of product could be formed? (aluminum’s atomic mass is 26.98 u and the atomic mass for a single iodine atom is 126.90 u). SHOW YOUR CALCULATIONS FOR FULL MARKS (3 points) 2 Al + 3 I2 → 2 Al(I)3 Can someone...
  4. S

    Physical chemistry problem

    The composition of vapour over a binary ideal solution is determined by the composition of the liquid. If Xa and Ya are the mole fraction of A in the liquid and the vapour respectively, find the value of Xa for which Ya-Xa has a maximum. What is the value of the pressure at this composition in...
  5. S

    Practice problem

    Can anybody please help me with the formula for this problem? "When charged particles are placed in an electric field, they accelerate to the kinetic energy, equal to the production of their charge and the applied potential difference. What potential difference (in volts) needs to be applied to...
  6. K

    Diazonium salt FOAM PRODUCTION PROBLEM (Balz-Schiemann)

    This was my attempt in a Balz-Schiemann reaction. In a three neck round bottom flask containing HCl i added a thermometer, a dropping funnel and a powder funnel. The flask was cooled in an ice bath. I slowly added some amount of m-phenylenediamine through the powder funnel. Then, I added...
  7. C

    Rate Law Problem

    The reaction of tert-butyl bromide with azide ion in aqueous solution is proposed to proceed by the following mechanism: (CH3)3CBr(aq) ⇌ (CH3)3C+(aq) + Br–(aq) where k 1 is the forward reaction and k -1 is the reverse reaction (CH3)3C+(aq) + N3–(aq) -> (CH3)3CN3(aq) k2 is the rate constant...
  8. C

    Chemistry Olympiad Rate Law Problem

    The reaction of tert-butyl bromide with azide ion in aqueous solution is proposed to proceed by the following mechanism: (CH3)3CBr(aq) ⇌ (CH3)3C+(aq) + Br–(aq) where k 1 is the forward reaction and k -1 is the reverse reaction (CH3)3C+(aq) + N3–(aq) -> (CH3)3CN3(aq) k2 is the rate constant...
  9. F

    Problem on most possible speed of gas

    To find the most possible speed of a gas, I know it is (2RT/M)^1/2 but how can i find out the speed of the gas mixture, let say 100:1 mixture of H2 and H2. Thank you!
  10. P

    Thermochemistry/Entropy problem

    For the reaction NO3(g) ---> NO2(g) + O(g) Would expected delta H be positive or negative? Would expected delta S (entropy) be positive or negative? Would reaction be spontaneous at all temperatures? Thank you
  11. M

    Energy problem

    Hi, I am not able to solve this problem. Any help? Avogadro constant: N=6.022*10^23(Number of atoms in 12 grams of atom) Calculate the energy in joules and power in watts when 2 kg of coal(Consisting only of carbon) is burnt for 1.5 hour. Assuming the equation:C+O2->CO2+4eV. And anyone please...
  12. S

    a buffer reated problem

    Calculate the H30 + (hydronium ion) concentration for a buffer solution of 2 M phosphonic acid and 1.5 M potassium hydrogen phosphate [Ka1= 7.11* 10^-3; Ka2=6.32x10^-8]. I found this problem. Firstly I feel that phosphonic acid is wrongly written, it should be phosphoric acid. Assumimng it as...
  13. S

    Mysterious half-life problem

    The problem says, "carbon dating may be used to date materials between 100 and 40,000 years old. The half-life of the first order decay of carbon 14 isotope is 5730 years. What percentage (=[C14]f/[C14]i) of carbon 14 remains in a sample after 40,000 years?" I easily found k but couldn't decide...
  14. A

    Physical Chemistry problem help

    I dont know wheather this problem is undergraduate level or no but here goes: Consider the following equilibria at temperature 'T' in Kelvin. 2A(g) ⇌ B(g) 2A(g) ⇌ C(g)+D(g) After the system reaches equilibrium ,it has been found that 20% of initial amount of A has been converted to C and D ,and...
  15. A

    Chemical equilibrium problem help

    Hi everyone. I am from Sri Lanka. My university entrance exams are coming up. Need help figuring out past paper problems mainly physical chemisrty. Any advice?
  16. S

    Oxygen pressure for oxidizing gold problem

    Hi Guys! I'm not sure what to do, I don't epect anyone to complete this for me (not that i'd be adverse to it) but can anyone give me some guidance please? The question is linked: http://imgur.com/0cXlnkB 2AU(solid) + 3/2O2(gas) <--> Au203(solid) @25degrees. Gibbs free energy change =...
  17. S

    heat reaction problem please help

    Hello everyone! this is my problem: How much energy is required to heat 29.72 g of H2Ofrom 10.00 degrees C to 37.50 degrees C? (heat capacity of H2O = 75.37 J/mol K) answer in Joules. this is what I did: 1- 29.72 g = 1.65 mol of H2O 2- Δt= 27.5 3- e=1.65 mol x 75.37 J/mol K x 27.5 therefore...
  18. M

    Need help with Enviromental Chemistry Problem

    Hello I have a question on my assignment that goes like this: A water sample has a pH of 8.21 and a total Ca2+ concentration of 143 ppm.(3 marks) What are the molar concentrations of CO32− and HCO3−? What is the total alkalinity of the water? I know that the total alkalinity= 2[CO32-)...
  19. E

    Stripping voltametry problem

    Hey. I am working on a Metrohm instrument, 797 VA Computrace 1.3, using HMDE as working electrode (Polarography). I am measuring between -1.2 V and +0.2 V. Recently the measured current keeps falling to 0 A at about -0.6 V or I am not measuring any current at all, although my mercury drop hasn't...
  20. B

    Calculating Ksp CHem 12 problem?

    A student determined that exactly 0.0533 g of manganese (ii) fluoride was dissolved in 800 mL water to make a saturated manganese (ii) fluoride solution. What is the Ksp for manganese (ii) fluoride? solubility related to [ions] reacted 0.0553 g MnF2 dissolves/800 mL * 1 mol/ 92.9g * 1 mol...