A certain weak acid, HA, with a Ka value of 5.61�10?6, is titrated with NaOH.
A) A solution is made by titrating 7.00mmol (millimoles) of HA and 2.00mmol of the strong base. What is the resulting pH?
B) More strong base is added until the equivalence point is reached. What is the pH of this solution at the equivalence point if the total volume is 38.0mL ?
WILL RATE IF BOTH ANSWERS ARE CORRECT WITH STEPS SHOWN
In: Chemistry
A.) What is the pH of a buffer prepared by adding 0.607 mol of the weak acid HA to 0.406 mol of NaA in 2.00 L of solution? The dissociation constant Ka of HA is 5.66×10−7. ANSWER IS: 6.072
B.) What is the pH after 0.150 mol of HCl is added to the buffer from Part A? Assume no volume change on the addition of the acid. ANSWER IS: 5.776
C.) What is the pH after 0.195 mol of NaOH is added to the buffer from Part A? Assume no volume change on the addition of the base.
I had to request the answer for part B but I don't know how to work the problem out. Please help me!
In: Chemistry
Transferrin is the iron-transport protein found in blood. It has a molecular mass of 81000 and carries two Fe3+ ions. Desferrioxamine B is potent iron chelator used to treat patient with iron overload. It has a molecular mass of 650 and can bind one Fe3+. Desferrioxamine can take iron from many sites within the body and is excreted (with its iron) through the kidneys. The molar absorptivities of these compounds are given in the following table. Both compounds are colorless (no visible absorption) in the absence of iron.
e (M-1 cm-1)
l (nm) Transferrin Desferrioxamine
428 3540 2730
470 4170 2290
(a) A solution of transferrin has an absorbance of 0.463 at 470 nm in a 1.000 cm cell. Find the concentration of transferrin in mg/mL and the concentration of iron in μg/mL.
(b) After addition of desferrioxamine (which dilutes the sample), the absorbance at 470 nm was 0.424 and the absorbance at 428 nm was 0.401. Calculate the fraction of iron in transferrin. Remember that transferrin binds two Fe3+ ions and desferrioxamine binds only one.
In: Chemistry
4. The enzyme alcohol dehydrogenase catalyzes the oxidation of ethyl alcohol by NAD+ to give acetaldehyde plus NADH and a proton:
CH3CH2OH + NAD+ CH3CHO + NADH + H+
The rate of this reaction can be measured by following the change in pH. The reaction is run in 1 mL 10 mM TRIS buffer at pH 8.6. If the pH of the reaction solution falls to 8.4 after ten minutes, what is the rate of alcohol oxidation, expressed as nanomoles of ethanol oxidized per mL per sec of reaction mixture?
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In the Bohr model, when an electron leaves one n orbit and enters another n orbit, a photon is either emitted or absorbed. Derive a relationship between the wavelength of the emitted or absorbed photon and the change in the DeBroglie wavelength of the electron when it moves from one n to another n.
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800 mL of a 2 M lactic acid buffer at pH=4.2 is mixed with 600 mL of a 1 M lactic acid buffer at pH=3.9. After the two buffer solutions are combined, 300 mL of 1.5 M sodium hydroxide is added to the buffer solution. What is the pH of the solution after the sodium hydroxide has been added? (lactic acid pKa = 3.86)
In: Chemistry
a. In Season 2 of Breaking Bad, Jesse and Heisenberg end up stranded in the desert because the battery of the RV is dead. Walter builds a homemade battery to jumpstart the engine. He uses brake pads that contain mercuric oxide (HgO) and galvanized steel which is a source of Zn metal. The electrolyte he uses is KOH. Relevant data can be found in Appendix B. (Below)
i. Write down the relevant half reactions.
ii. What is the overall spontaneous electrochemical reaction?
iii. Calculate the standard potential for this reaction.
iv. If the pH of the electrolyte is 12 and the concentration of zinc ions is 0.01 M what is the cell potential?
b. Silver can be electroplated at the cathode of an electrolysis cell by the half-reaction:
Ag+(aq) + e- ---> Ag(s)
What mass of silver would plate onto the cathode if a current of 6.8 A flowed through the cell for 72 min?
Appendix B: Standard reduction potentials for selected half reactions
|
Half reaction |
E0red (V) |
|
O2(g) + 4H+(aq) + 4 e- ® 2 H2O(l) |
1.23 |
|
Hg22+(aq) + 2 e- ® 2 Hg(l) |
0.85 |
|
Ag+(aq) + e- ® Ag(s) |
0.80 |
|
Fe3+(aq) + e- ® Fe2+(aq) |
0.77 |
|
HgO(s) + H2O (l) + 2e- ® Hg(s) + 2OH- |
0.098 |
|
2H+(aq) + 2 e- ® H2(g) |
0.00 |
|
Ni2+(aq) + 2 e- ® Ni(s) |
-0.26 |
|
Cd2+(aq) + 2 e- ® Cd(s) |
-0.40 |
|
Zn2+(aq) + 2e- ® Zn(s) |
-0.76 |
|
2 H2O(l) + 2 e- ® H2 + 2 OH-(aq) |
-0.83 |
|
Na+(aq) + e- ® Na(s) |
-2.71 |
I need to know how to do these questions not just the answers, thank you!
In: Chemistry
Which of the following statements about the effective nuclear charge (Zeff) is correct?
| a. |
Zeff increases across a period and is relatively constant down a group. |
|
| b. |
Zeff decreases across a period and increases down a group. |
|
| c. |
Zeff increases with the size of the atom. |
|
| d. |
Zeff increases as the value of the principal quantum number increases. |
|
| e. |
Zeff is greater for hydrogen than for any other element. |
In: Chemistry
You titrate 100 mL of a .0250 M solution of benzoic acid (HBz) with .100 M NaOH to the equivalence point. Devolop a titration curve for this reaction when 0.00, 6.25, 12.5, 24.5, 25.0, 25.5, and 26 mL of titrant is added
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Write the appropriate nuclear equation for the following description- K-40, a beta-particle emitter, is a naturally occurring potassium isotope found in some foods
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For the following half reaction: N2(g) + 5H+(aq)+4e- ----> N2H5+
Calculate the amount of time required to produce 7.86 (g) of N2 while using a 15.0 A current.
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Why is ΔH from the neutralization of HCl with NaOH is greater than that evolved for the neutralization of CH3COOH with NaOH?
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Ba(NO3)2 + NaIO3 + H2O → Ba(IO3)2·H2O + NaNO3
5.274 g of barium iodate monohydrate was synthesized by a student by adding 30.00 mL of 5.242 x 10-1 M Ba(NO3)2 to 50.00 mL of 8.221 x 10-1 M NaIO3.
Calculate the theoretical yield of Ba(IO3)2·H2O in grams.
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Brownstock pulp and associated black liquor is stored in the blowtank after batch kraft cooking. From the blow tank it is pumpe at 12% consistncy to a diffuser washer(Modified norden equal to 5) followed by a vaccum drum washer(modified norden equal to 3). The dilution factor for the washing operation is 2kg fresh water per kg of dry pulp. The pulp and wash liquor move countercurrently in three washers. after the drum washer the pulp becomes part of the countercurrently flowing wash water.
Calculate the washing efficiency E in % for the total washing operation using the formula below which is valid for 12% pulp consistency throughout the washing system: E=100(1-.(1364(DF))/(1+.1364(DF)N+1-1) N- total number of mixing stages DF- net amount of water added(kg/kg pulp)
Also calculate the overall washing efficiency for the entire system of washers and press.
E0=[TF+(1-TF)DR]100
TF=(Win - Wout )/ Win
W= (100- consistency)/consistency
DR=(Cv-Cs)/(Cv-Cw)
Cv= vat solid solution, Cw= wash solids concentration, Cs= solids concentration in sheet leaving water
In: Chemistry