Consider the titration of 65 mL of 1.75 M diethylamine, (CH3CH2)2NH (Kb = 1.3×10-3) with 0.25 M HCl. How many mL of HCl will need to be added to the diethylamine solution to reach a pH of 11.11?
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2. Phosphoric acid (H3PO4) is a triprotic acid with the following pKa values: pKa1 = 2.15 pKa2 = 7.20 pKa3 = 12.35
a). You wish to prepare a 1.000 L of a 0.0450 M phosphate buffer at pH 6.8. Which of the following salts do you use (PICK 2) and what mass of each salt will you add to the mixture? H3PO4 (M.W.= 97.995) KH2PO4 (M.W.=136.086) Na2HPO4 (M.W.=141.959) AlPO4 (M.W.=121.953) 2
b). A concentrated phosphate buffer known as “phosphate buffered saline” (or PBS) is made with the salts you choose from above in addition to NaCl and KCl. The 10x concentrated solution has a pH ~6.8 and the 1x concentrated (i.e., diluted with water) solution is ~7.1. Why?
c). You accidently grabbed the 10x concentrated phosphate buffered saline (or 10xPBS) instead of the 1xPBS solution and start to adjust the pH of your buffer with NaOH to reach your desired buffer pH. You notice it is taking much more base than with your usual 1xPBS buffer. Why?
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Compound X, C8H17Cl, is a
chiral product of the radical chlorination of
4-methylheptane.
X reacts in SN2 fashion with NaI in
acetone to form Z, C8H17I.
When the reactant is the R-enantiomer of X, only
the R-enantiomer of Z is formed.
Draw a structural formula for X; do not show
stereochemistry.
I don't even know how to go about this, I have been trying to do
these types of problems for a while now and can't seem to get one
right
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Using the mechanism of hydroboration-oxidation as an example, explain what is meant by reterntion of configuration.
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Potassium dichromate (K2Cr2O7) is a bright orange salt that can be converted to a blue-violet solution of Cr3+ ions. Under certain conditions, K2Cr2O7 reacts with ethanol (C2H5OH) to produce carbon dioxide gas. The legal definition of intoxication is a blood alcohol (C2H5OH) level of 0.08% by mass or higher. In a given case, 35.48 mL of 0.05182 M K2Cr2O7 was required to titrate a 50.02 g sample of blood. From the tested sample, should the person be arrested for a DUI?
Assume that only the ethanol reacts with the potassium dichromate.
C2+H5+OH (l) + K2Cr2O7 (aq) ----> CO2 (g) + K++ Cr3+
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Suppose the 0.1 M Zn 2+ solution has been diluted (instead of the Cu 2+ solution), would the measured cell potentials have increased or decreased? Explain why the change occurred.
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access important values if needed for this question.
A piece of solid lead weighing
38.4 g at a temperature of 315 °C
is placed in 384 g of liquid lead
at a temperature of 372 °C. After a while, the
solid melts and a completely liquid sample remains. Calculate the
temperature after thermal equilibrium is reached, assuming no heat
loss to the surroundings.
The enthalpy of fusion of solid lead is
ΔHfus = 4.77 kJ/mol at its melting
point of 328 °C, and the molar heat capacities for
solid and liquid lead are Csolid =
26.9 J/mol K and Cliquid =
28.6J/mol K.
Tfinal = °C
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1. If the boiling point of (R,R)-1,2-diaminocyclohexane is 110°C, what do you think the boiling point of (S,S)-1,2-diaminocyclohexane is?
2. Based on measured roations, how can one predict how well one separated 1,2-diaminocyclohexane enantiomers? Please explain the answer and how results could be improved (how you can better separate the two enantiomers)
thankyou
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After thoroughly reviewing the octet rule, respond to the following: Discuss the octet rule and why there are exceptions to the rule. Give examples of the rule and of exceptions written in 250 words minimum
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LCAO: Determine which of the following statements are true of a 2p atomic orbital
Which of the following statements are true of a 2p atomic orbital? You may find the Orbitron page for the 2p orbital useful.
| 1. The wavefunction Ψ has the same sign at all points. |
| 2. The orbital possesses an inversion center. |
| 3. Any radial line that starts at the nucleus and travels outward will always encounter a single point where the wavefunction Ψ has a value of zero. |
| 4.The orbital possesses one spherical node. |
| 5. The orbital possesses one nodal plane (angular node). |
| 6. The largest values of wavefunction and electron density are found at the nucleus. |
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Consider the reaction that results from the addition of 50.0 g of Zinc metal (Zn) to 60.0 g of hydrochloric acid (HCl)? Generate a balanced equation for this reaction and then answer the folling (3) questions.
1) What is the limiting reactant?
A) zinc
B) hydrochloric acid
C) zinc chloride
D) hydrogen gas
E) hydrogen gas
2) How much hydrogen gas forms?
A) 2.68g
B) 0.77g
C)0.83g
D) 8.35g
E) 1.55g
3) How much excess reagent is left over?
A) 4.26g
B) 22.13g
C) 11.9g
D) 9.43g
E) 4.35g
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HWW Item 810
Part A
Titanium reacts with iodine to form titanium(III)iodide,
emitting heat.
2Ti(s)+3I2(g)→2TiI3(s)ΔHorxn = -839 kJ
Determine the masses of titanium and iodine that react if 1.50×103 kJ of heat is emitted by the reaction.Express your answer to three significant figures and include the appropriate units.
m(Ti)= (value)(unit)
m(I2)= (value)(unit)
Part B
Consider the following generic reaction: A+2B→C+3D, with ΔH = 128 kJ . Determine the value of ΔH for each of the following related reactions.
a) 3A+6B→3C+9D
ΔH = _____ kJ
b) C+3D→A+2B
ΔH = _____ kJ
c) 1/2C+3/2D→1/2A+B
ΔH = _____ kJ
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