As a very rough approximation, an electron in a quantum dot can be thought of as an electron in a 3D box. By analogy to the 2D box, write down an expression for the energy levels for an electron in a 3D box (write an expression for the special case of a cubic box, with all sides having a length L)

1. What are the 4 molecular structure of polymers? Write down the relationship between materials's strength and different molecular structure?

2. What are the three phases that a composite has, and what are their roles in the composite?

3. Give 3 examples for the materials that can be used as matrix phase and reinforcement phase.

4. What is the reason of using plies in different directions for some of the laminate composites?

Arsenic acid (H3AsO4) has Ka values of 2.5 x 10–4, 5.6 x 10–8, and 3 x 10-13. What is the concentration of the HAsO42- dianion in a solution whose initial arsenic acid concentration was 0.35 M?

2 KMnO4 + 16 HCl = 5 Cl2 + 2 KCl + 2 MnCl2 + 8 H2O

If you react 22.7 grams KMnO4 with 48.6 grams HCl

a) how much KCl will be produced?

b) How much of the excess reactant will remain after the reaction has come to an end?

When 100 mL each of 2.0 × 10-4 M Ca2+ and 2.0 × 10-2 M F- are mixed, what is the remaining Ca2+ ion concentration ? The solubility product constant of CaF2 is 5.3 × 10-9. (Hint: Determine the limiting reactant, the concentration of excess reactant after precipitation, and how the concentration of excess reactant influences the solubility of CaF2).

The visible emission spectrum of hydrogen involves a transition to n final = 2. What is initial for the line of the emission spectrum at 434 nm? a. 5 b. 6 c. 4 d. 3 e. 7

Problem 15.61 Which of the following gives a buffer solution when equal volumes of the two solutions are mixed? Check all that apply. a) 0.20 M NH3 and 0.10 M HCl b) 0.20 M NH4Cl and 0.10 M NaOH c) 0.10 M NH3 and 0.10M HCl d) 0.10 M NH4Cl and 0.10M NH3

The octane rating of gasoline is a relationship of the burning efficiency of the given gasoline mixture to the burning efficiency of octane (C8H18). (Figure 1) Like most hydrocarbons, octane reacts with oxygen gas to produce carbon dioxide and water. The unbalanced equation for this reaction is

C8H18(g)+O2(g)→CO2(g)+H2O(g)

1-Determine the balanced chemical equation for this reaction.

C8H18(g)+O2(g)→CO2(g)+H2O(g)

0.270 mol of octane is allowed to react with 0.660 mol of oxygen. Which is the limiting reactant?

2- 0.270  of octane is allowed to react with 0.660  of oxygen. Which is the limiting reactant?

3-How many moles of water are produced in this reaction?

4-After the reaction, how much octane is left?

A lagoon with volume of 1200 m³ has been receiving a steady flow of a conservative (inert) waste at a rate of 100 m³ /day for a long enough time to assume that steady-state conditions apply. The waste entering the lagoon has a concentration of 10 mg/L.

a) What would be the concentration of pollutant in the effluent leaving the lagoon?

b) If the input waste concentration suddenly increased to 100 mg/L, what would the concentration in the effluent be 7 days later?

So I have a lab practical coming up; how do I know when to take an IR spec versus making a TLC chamber?

Follow up question: Can someone walk me through the interpretation of a TLC chamber?

why should be insoluble in water CaCO3

Calculate [ Hg₂²⁺ ] in saturated solutions of Hg₂Br2 in:

a. 0.100 M KNO₃

b. 0.001 M KBr

Note: K_sp for Hg₂Br₂ = 1.2 ⨯ 10^-18​

A 135-lb person absorbs 3.3 10-7 J of energy from radioactive emissions. How many rads does she receive? (1 kg = 2.205 lb) 1 rad= .01J/kg

If ℓ= 1, what can you deduce about n?

an experiment was preformed under identical conditions as yours. The absorbance of the penny solution was recorded as 0.231 absorbance units. A calibration plot of absorbance vs concentration of cu(II) (mM) yielded the following trendily equations y= 11591x +.50

a. What is the concentration of the original penny solution?

b. How many grams of Cu are in this solution?

c. if the percent Cu was determined to be 2.70 percent what was the mass of the penny?