CDs and DVDs are read optically using lasers. A typical laser used to read a compact disc emits photons of wavelength ~670 nm (in the red region of the visible spectrum) and has 1.0 mW power.

How many photons are emitted by this laser per second?

Blu-ray devices (i.e. blue laser diodes, based on GaN) are becoming more popular than DVDs for optical data storage.   What is the advantage of using shorter wavelength lasers for this purpose?

When an organic sulfate ester is hydrolyzed by a sulfatase enzyme, a hydrogen ion is produced;

R-O-SO₃^- + H₂O ----> ROH + SO₄^-2 + H⁺

The above reaction was carried out in a 1.0 mL of a .02 M Tris buffer, pH 8.10, containing 0.01 M ester. At the end of 10 minutes, the pH of the reaction mizture decreases to 7.95. How many micromoles of ester were hydrolyzed during the 10 minute reaction period? pKa of Tris = 8.10.

Researchers wish to know if the data they have collected provide sufficient evidence to indicate a difference in mean serum uric acid levels between normal individuals and individuals with Down’s syndrome The data consist of serum uric acid readings on 12 individuals with Down’s syndrome and 15 individuals without Down’s syndrome. The means are x1=4.5 mg/100 ml for those with Down’s syndrome and x2=3.4 mg/100 ml for those without. s₁ = 1.0 and s₂ = 1.2.

Will literally worship you if you can give me some assistance with these. (I rate immediately)

Consider the reaction. A(g)⇌2B(g) Find the equilibrium partial pressures of A and B for each of the different values of Kp. Assume that the initial partial pressure of B in each case is 1.0 atm and that the initial partial pressure of A is 0.0 atm. Make any appropriate simplifying assumptions.

Part A

Kp= 1.6

Part B

Kp= 1.5×10−4

Part C

Kp= 1.6×105

A lead cube is cut that is 1.500 cm on each side. The density of lead is 11.35 g/cc. How many atoms of lead are in the cube if only 60% of the cube is occupied by lead atoms? Use "E" for scientific notation.

A copper atom has a diameter of 128pm. How many centimeters is a line containing exactly 1.0 moles of copper atoms sequentially arranged? Use "E" for scientific notation.

Calculate the mass ( in grames) of cobalt that has the same number of atoms as 521 mg of silicon.

Which of the followings give greater voltage than E◦cell in the reaction of Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)? [E◦cell = 1.10 V] Select one: A. [Zn2+]= 1.0x10-6 M, [Cu2+] = 1.5 x 10-5M B. [Zn2+]= 1.0x10-6 M, [Cu2+] = 1.0x10-6M C. [Zn2+]= 1.0x10-4 M, [Cu2+] = 1.0x10-6M D. [Zn2+]= 1.0 x10-6 M, [Cu2+] = 1.5 x 10-6M

1. Scuba drivers breathing air at increased pressure can suffer from nitrogen narcosis-a condition resembling drunkenness-when the partial pressure of nitrogen exceeds about 4 atm. What property of gas/water solutions causes this to happen?

2. Calculate the mass of nitrogen dissolved at room temperature in an 80.0 L home aquarium. Assume a total pressure of 1.0 atm and a mole fraction for Nitrogen of 0.78. (K_H for N2 = 6.1 x 10^-4 M/atm)

A. The pH of an aqueous solution of 0.345 M hydrocyanic acid is ____

B. The pH of an aqueous solution of 0.345 M triethanolamine (a weak base with the formula C₆H₁₅O₃N) is ____.

C. The pH of an aqueous solution of 0.221 M ammonium iodide, NH₄I (aq), is ______.

This solution is _________(acidic,basic,neutral)

D. A buffer solution is 0.315 M in H2S and 0.258 M in . If Ka1 for H2S is 1.0 x 10^-7, what is the pH of this buffer solution?

pH = ________

Please answer all, if not as many as possible! Thank you (:

a) Liquid nitrogen, which has a boiling point of 77 K, is commonly used to cool substances to low temperatures. How much energy must be removed from 1.0 kg of gaseous nitrogen at 77 K for it to completely liquefy?

b) How much energy is needed to melt 0.225 kg of lead so that it can be used to make a lead sinker for fishing? The sample has an initial temperature of 27.3°C and is poured in the mold immediately after it has melted.