Answers created by Truong-Son N.

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• How much heat is needed to heat #"25.0 g"# of ice from #-25^@ "C"# into steam at #115^@ "C"#?
  
• For two aqueous solutions, one containing urea and the other containing scandium(III) nitrate, with the same extent of freezing point depression, which of the following is true?
  
• d_z2 orbital participate in sp^3d hybridization and not any other d-orbital.why?
  
• For the equilibrium #CuSO_4. 5H_2O(s) rightleftharpoons CuSO_4. 3H_2O(s) + 2H_2O(g)#, #K_p = 2.25*10^(-4) atm^2# and vapour pressure of water is #22.8# Torr at 298K?
  
• What are the constitutional isomers of dimethyl cyclopentane?
  
• What mass of carbon dioxide is present in 1.00 m3 of dry air at a temperature of 21 ∘C and a pressure of 649 torr ?
  
• What is the VSEPR shape of #(SO_4)_2?#
  
• Question #6b37a
  
• First ionization energy of hydrogen atom= 2.18 aJ (attojoules). What the frequency and wavelength, in nanometers, of photons capable of just ionizing hydrogen atoms?
  
• How do you use spherical Bessel functions of the first and second kind to solve the following ordinary differential equation?
  
• Why do molecules with multiple bonds not considered to have more electron groups than molecules with single bonds?
  
• Given concentrated hydrochloric at #10.6*mol*L^-1#, how do we prepare a #2*L# volume of #HCl# at #2.5*mol*L^-1# concentration?
  
• If the boiling point elevation of an aqueous solution containing a non-volatile nonelectrolyte is 0.48◦C, what is the molality of the solution?
  
• #1)# What is the change in internal energy of combustion in #"kJ/mol"# for a bomb calorimeter whose heat capacity is #"3024 J/"^@ "C"# that has raised in temperature by #1.2910^@ "C"# due to the combustion of #"0.1575 g Mg"#? Also help with one more?
  
• Why do transition metals have variable oxidation states?
  
• Why is a reaction spontaneous when Delta G < 0?
  
• For which of the following reactions is ΔH∘rxn equal to ΔH∘f of the product(s)?
  
• Prove the trig identity?
  
• If #"45.0 g"# of methanol, #"22.0 g"# of acetone, and #"120.0 g"# of water are combined, what is the mol fraction of methanol?
  
• Can #1/2H_2# be considered as a single hydrogen atom?
  
• Why does Bohr's model of the atom violate the Heisenberg Uncertainty Principle?
  
• How many compound can be obtained in good yield by wurtz reaction ?
  
• Which of the following is most stable carbocation and why?
  
• What is the minimum molar concentration of hydroxide ions needed to selectively precipitate chromium(III) hydroxide from a mixture of #"0.025 M"# #"Ca"^(2+)# and #"0.0050 M"# #"Cr"^(3+)#?
  
• Identification of a ion from the highest energy line in its emission spectrum?
  
• What is the oxidation state of iron in #"Fe"_3["Fe"("CN")_6]_2#?
  
• Pressure over #1000ml# of a liquid is gradually increased from #1# bar to #1001# bar under adiabatic conditions. If the final volume of the liquid is #990ml#, calculate #DeltaU# and #DeltaH# of the process?
  
• What is the effect on the concentration of Fluorine when stress is added to this equilibrium system?
  
• What is a general rule for achieving thermodynamic stability?
  
• Please give the proper reason with details in this question?
  
• Question #a4a33
  
• What orbitals are used in the sigma bond of #"O"_2#?
  
• What is the value of #gamma# for a polyatomic gas?
  
• How do I calculate where the nodal planes are on any given molecular orbital?
  
• How do you convert #"CH"_3"COOH"# to #"C"_2"H"_4"O"_2#?
  
• What is the concentration of ferrous ion?
  
• Order in the increasing order of acidity:HCl, H2SO4, HF, HCl, HI, HBr, HNO3, HBrO, HClO, HClO3, HClO4, H2S, H3PO4(?)
  
• What is the change in enthalpy for this gas-phase reaction between potassium and bromine?
  
• Explain Fajan's rules? Why are elements with electron configuration #(n−1)d^n ns^0 np^0# more polarizing in nature as compared to the cations having noble gas electronic configuration #ns^2np^6#?
  
• Is there a formula for the number of elements in any given period of the periodic table?
  
• Why is rhenium frequently used as a catalyst? What properties does it have that lend to it being a good catalyst?
  
• Is #"BI"_3# polar?
  
• What is the hybridization of benzene?
  
• For standard conditions, is the activity of #"1 M"# arbitrary?
  
• For a spontaneous process in an isolated system, the change in entropy is positive. Why? Why not?
  
• Question #8cf3a
  
• What mass of sucrose was dissolved in #"100 g"# of water to lower its freezing point by #1^@ "C"#? #K_f = -1.86^@ "C/m"#.
  
• Addition of 1kg of non volatile solute in volatile solvent increases the boiling point from 350K to 355K and decreases the freezing point from 250K to 220K.If Kb is 15.5KKg/mol,then Kf will be?
  
• Explain this exception to the general trend of ionization energy in terms of electron arrangements and attraction/repulsion?
  
• What is the McLafferty rearrangement in mass spectrometry?
  
• Why binding energy (Mettalic bond ) of Mn is less than Cr??
  
• The heat of hydrogenation of ethene is #x_1# and that of Benzene is #x_2#. Hence resonance energy is?
  
• A gas mixture #3.67L# in volume contain #C_2H_4# and #CH_4# in proportion of #2:1# by moles and is at #25^oC# and 1atm. If the #DeltaH_c(C_2H_4)# and #DeltaH_c(CH_4)# are #-"1400 kJ/mol"# and #-"900 kJ/mol"# find heat evolved on burning this mixture?
  
• How do you begin from the Gibbs-Helmholtz equation to determine the new temperature at which a reaction ceases to become spontaneous? What fundamental assumptions are involved?
  
• The standard enthalpy of formation of #H_2(g)# is zero. But sometimes we do write( which is also given in my book) #2H(g) -> H_2#; #DeltaH = -"435 kJ/mol"#. This surely suggests that the enthalpy of formation of #H_2# is non-zero?
  
• In #"2 L"# of a #"2.00 M"# solution of #"AgNO"_3#, which of the following is/are true?
  
• What is the mass of octane burnt and calculating the energy released? Full Question in the description box below.
  
• Calculate for the first-excited state #psi_1(x)# of the simple harmonic oscillator the value of the Heisenberg Uncertainty relation?
  
• If an electron with a position uncertainty of #"1 Å"# has been accelerated through a potential difference of #"6 V"#, what is the uncertainty in the de Broglie wavelength?
  
• What is the mass of silver ring? (Assume a density of 0.998 g/mL for water.)
  
• How would we know that #"Ni"("CO")_4# prefers tetrahedral over square planar?
  
• For an isothermal process, S = __________?
  
• How do you balance the following redox reaction? I got #"Cu"(s) + 2"H"^(+)(aq) + "NO"_3^(-)(aq) -> "Cu"^(2+)(aq) + "NO"_2(g) + "H"_2"O"(l)# which is not right...
  
• How I do the THEORETICAL calculation of solubility?
  
• What is the name of #("H"_3"C")_3"CC"("CH"_3)_3#?
  
• Can the entropy of an ideal gas change during an isothermal process?
  
• What is the average kinetic energy and velocity of nitrogen gas molecules at 273 K and at 546 K?
  
• What is the molar mass of a gas if #"96 g"# of it exists in a #"52 L"# container at #"700 mm Hg"# pressure and #25^@ "C"#?
  
• Is energy a state function?
  
• A compound containing only carbon and hydrogen has a carbon-to-hydrogen mass ratio of 11.89. Which carbon-to-hydrogen mass ratio is possible for another compound composed only of carbon and hydrogen?
  
• What is the value of the principal quantum number, n, for the hydrogen s orbital matching these curves?
  
• What is nitrogen inversion?
  
• What is the pH of a 25 ml solution of 0.1 N HCl?
  
• Starting with #(epsilonA_(s,r)sigma)/(rhoVc)int_(0)^(t)dt = int_(T_i)^(T) 1/(T_(sur)^4 - T^4)dT#, show that . . . ?
  
• Critical temperature for CO2 and CH4 are 31.1º and 81.9º C respectively. Which of these has stronger intermolecular forces and why ?
  
• Calculate the ratio of acetate to acetic acid for an acetic acid/acetate buffer to which strong base was added to result in a pH of #5.76#? #K_a = 1.8 xx 10^(-5)#.
  
• What is the freezing point depression of a solution containing 100g of ethanol (#C_2H_5OH#) in 0.750 kg of water?
  
• For the gas-phase reaction #"OF"_2(g) + "H"_2"O"(g) -> "O"_2(g) + 2"HF"(g)#, the nonzero enthalpies of formation are #23.0#, #-241.8#, and #-"268.6 kJ/mol"#, respectively. What are the #DeltaH_(rxn)^@# and #DeltaU_(rxn)^@# in #"kJ/mol"#?
  
• The solubility of Pb(OH)2 in water is 6.7 *10^-6 M.What is its solubility in a buffer solution of pH=8 ?
  
• What is the mass of air in the room? (Question-image from the description box) below
  
• What is the volume of 1 tons CO2 in supercritical condition?
  
• What is the pH of a solution that is 0.20 M in HF and 0.40 M in NaF? [Ka = 7.2*10^-4] I know the answer is 3.44 but could someone please explain how they got it? Thank you so much!!!! (:
  
• What is a quantum number set for Arsenic?
  
• How to calculate dipole moment of #"NH"_3#?
  
• Transition elements, such as chromium, are likely to have what type of oxidation number?
  
• Explain the difference between Orgel and Tanabe-Sugano diagrams?
  
• How do you correctly round this problem #(30.00 g)/ (10.0 mL)#?
  
• Insulin (#("C"_2"H"_10"O"_5)_n#) is dissolved in a suitable solvent at #20^@ "C"#. The slope of a plot of osmotic pressure (#Pi#) against #c# is found to be #4.65xx10^(-3)#. The molecular weight of insulin is?
  
• How do molecules vibrate?
  
• Question #9326b
  
• Explain why #Gd^(3+)# is colorless?
  
• What color is the #"NO"_2(g)# that forms when #"NO"# reacts with ozone in the atmosphere?
  
• What substance has a density that increases when temperature is increased?
  
• Given the reaction #2"Al"(s) + 6"HCl"(aq) -> 2"AlCl"_3(aq) + 3"H"_2(g)#, if #"0.15 mols"# of #"Al"# is to react with #"0.35 mols"# of #"Cl"#, how many mols of #"Al"# are in excess?
  
• How many mols of #"CO"_2# are made in photosynthesis?
  
• What happens to the volume when a substance is heated?
  
• What is the formula for calculating a nodal point?
  
• How would you summarize the second Law of Thermodynamics?
  
• What are the conditions for standard enthalpy of formation?
  
• What is the Fermi level? I heard it is also called the chemical potential.
  
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