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)
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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!
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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. |
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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
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In a common classroom demonstration, a balloon is filled with air and submerged in liquid nitrogen. The balloon contracts as the gases within the balloon cool. Suppose the balloon initially contains 2.90 L of air at a temperature of 21.5 ∘C and a pressure of 0.996 atm .
Part A
Calculate the expected volume of the balloon upon cooling to -196 ∘C (the boiling point of liquid nitrogen). When the demonstration is carried out, the actual volume of the balloon decreases to 0.61 L.
Part B
Can you explain the difference between the observed volume of the balloon and calculated value?
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Many economists favor a carbon tax as a way to discourage CO2 emissions. Suppose such a tax were to be set at $20 per ton (907kg) of carbon emissions as (CO2). Consider a 50-MW, 35% efficient power plant that uses coal with a carbon intensity of 24gC/MJ.
a. How much per year would this power plant pay in carbon tax?
b. Suppose a tree plantation sequesters (removes from the atmosphere and stores in biomass) 20,000kg of carbon dioxide per year per acre over the next 40 years the trees are growing (after which time the forest is mature and no further accumulation occurs). What area of forest would have to be planted to offset the power plant’s emissions over the next 40 years (roughly the lifetime of the power plant)?
c. What is the maximum the power plant owners would be willing to pay for this forest per acre? (do not use discounting)
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a) A 2.5 L sample of gas at 25oC is heated to 50oC at constant pressure. What is the final volume? b) What temperature would be required to increase the volume from 2.5 L to 6.0 L?
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Calculate the hydronium ion concentration in 0.120 M
nitrous acid. ka( nitrous acid) =7.1x10^4. Use the ICE method to
determone concentration of H3O+ = 9.23 x10^—3
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