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Question
A red laser pointer emits light at a wavelength of 488 nm. If the laser emits 7.5 10-4 J of energy per second in the form of visible radiation, how many photons per second are emitted from the laser?
A.4.1 10-19 photons/sec
B.5.4 10-16 photons/sec
C.8.9 1014 photons/sec
D.1.8 1015 photons/sec
E.2.5 1018 photons/sec
Answer
This answer is hidden. It contains 2 characters.
Related questions
Q:
Hydrogen peroxide decomposes into water and oxygen in a first-order process.
H2O2(aq) H2O() + 1/2 O2(g)
At 20.0 C, the half-life for the reaction is 3.92 104 seconds. If the initial concentration of hydrogen peroxide is 0.52 M, what is the concentration after 7.00 days?
A.1.2 10-5 M
B.0.034 M
C.0.074 M
D.0.22 M
E.0.52 M
Q:
A student analyzed a first-order reaction and obtained the graph below. Unfortunately, the student forgot to label the axes. What are the correct labels for the x and y axes? A.x axis = time, y axis = ln[A]
B.x axis = ln[time], y axis = [A]
C.x axis = ln[time], y axis = [A]
D.x axis = time, y axis = 1/[A]
E.x axis = 1/time, y axis = 1/[A]
Q:
________ are colloidal dispersions of one liquid in another liquid.
Q:
Aqueous colloidal solutions can be classified as ________ (water-fearing), or hydrophilic (water-loving).
Q:
A(n) ____ is a colloidal dispersion of a solid in a liquid.
A.gel
B.emulsion
C.aerosol
D.foam
E.sol
Q:
At 25 C, what is the osmotic pressure of a homogeneous solution consisting of 21.0 g urea (CON2H4) diluted with water to 2.50 L? (R = 0.08206 Latm/molK)
A.0.205 atm
B.3.42 atm
C.8.55 atm
D.12.3 atm
E.147 atm
Q:
Which of the following statements concerning osmosis is/are CORRECT?
1/ Osmosis involves the movement of ions through a semipermeable membrane until the charges on both sides of the membrane are equal.
2/ Solvents move from regions of low solute concentration to regions of higher solute concentration.
3/ Osmotic pressure is a colligative property.
A.1 only
B.2 only
C.3 only
D.2 and 3
E.1, 2, and 3
Q:
What is the boiling point of a solution containing 0.852 g naphthalene(C10H8, molar mass = 128.2 g/mol) dissolved in 14.0 g benzene? The boiling point of pure benzene is 80.10 C and the boiling point elevation constant, Kbp, is 2.53 C/m.
A.78.70 C
B.80.25 C
C.81.30 C
D.82.50 C
E.85.43 C
Q:
Assuming ideal behavior, which of the following aqueous solutions should have the highest boiling point?
A.1.00 m LiBr
B.0.75 m K2SO4
C.0.50 m Ca(NO3)2
D.0.75 m NaCl
E.1.25 m C6H12O6
Q:
The Henry's law constant for O2 in water at 25 C is 1.3 10-3 mol/kgbar. What partial pressure of O2 (in atm) is necessary to achieve an equilibrium concentration of 2.9 10-3 mol/kg O2? (1 atm = 0.9869 bar)A.0.44 atmB.0.45 atmC.2.1 atmD.2.3 atmE.3.8 atm
Q:
Which of the following statements concerning solubility is/are CORRECT?
1/ Ionic compounds composed of Group 1A metal ions and halide ions, such as NaCl, are insoluble in nonpolar solvents.
2/ The solubility of the halogens (Cl2, Br2, and I2) in polar solvents is greater than their solubility in nonpolar solvents.
3/ The solubility of polar molecules, such as sugar, in polar solvents is generally greater than their solubility in nonpolar solvents.
A.1 only
B.2 only
C.3 only
D.1 and 3
E.1, 2, and 3
Q:
Two nonpolar solvents, such as hexane and carbon tetrachloride, may be miscible even though the enthalpy of mixing of these liquids might be small. A reason that mixing occurs is that mixtures have greater disorder than pure solvents. The tendency toward disorder is a thermodynamic function called ____.
A.entropy
B.enthalpy
C.saturation
D.adhesion
E.cohesion
Q:
A 15 meter by 12 meter pool of water has a depth of 2.2 meters. What mass of silver ion is present in the reservoir if the concentration of silver ion is 0.14 ppm? (1 m3 = 1000 L; assume the density of the solution is 1.00 g/mL)A.5.5 10-4 gB.5.5 10-2 gC.0.55 gD.5.5 gE.55 g
Q:
If the molality of a NaBr(aq) solution is 2.50 m, what is the weight percent of NaBr? The molar mass of NaBr is 102.9 g/mol.
A.20.5%
B.25.0%
C.25.7%
D.34.6%
E.65.4%
Q:
What is the definition of molality?
A.moles of solute per kg of solvent
B.grams of solute per kg of solution
C.grams of solute per liter of solution
D.moles of solute per liter of solvent
E.moles of solute per liter of solution
Q:
What process occurs when the temperature of a substance is at Point A increased (at constant pressure) until the substance is at Point B? A.condensation
B.vaporization
C.sublimation
D.melting
E.freezing
Q:
Which process requires the greatest endothermic change in enthalpy for water?
A.freezing
B.condensation
C.sublimation
D.melting
E.vaporization
Q:
Magnesium sulfide (molar mass 56.37 g/mol) has a face-centered cubic unit cell with magnesium ions in octahedral holes. The ionic radii of magnesium ions and sulfide ions are 79 pm and 184 pm, respectively. What is the density of MgS (in g/cm3)?
A.1.29 g/cm3
B.2.57 g/cm3
C.3.64 g/cm3
D.5.15 g/cm3
E.7.28 g/cm3
Q:
Which of the following statements is/are CORRECT? If an ionic compound with the formula MX forms a face-centered cubic unit cell with the anions (Xn-) at the lattice points, the cations (Mn+) may occupy1/ one fourth of the tetrahedral holes in each unit cell.2/ all of the octahedral holes in each unit cell.3/ the center of each face in each unit cell.A.1 onlyB.2 onlyC.3 onlyD.1 and 2E.1, 2, and 3
Q:
Lithium chloride crystallizes in a face-centered cubic unit cell with chloride ions occupying the lattice points and lithium ions occupying octahedral holes. How many chloride ions surround each lithium ion in LiCl?
A.1
B.4
C.6
D.8
E.12
Q:
What is the distance, in atomic radii, along any edge of a body-centered unit cell?
A.
B.2 r
C.4 r
D.
E.r
Q:
If a metal crystallizes in a primitive cubic lattice, each metal atom has ____ "nearest neighbors."
A.3
B.4
C.6
D.8
E.12
Q:
If a metal crystallizes in a face-centered cubic lattice, each metal atom has ____ "nearest neighbors."
A.3
B.4
C.6
D.8
E.12
Q:
Arrange the three common unit cells in order from least dense to most dense packing.
A.face-centered cubic < body-centered cubic < primitive cubic
B.primitive cubic < body-centered cubic < face-centered cubic
C.primitive cubic < face-centered cubic < body-centered cubic
D.body-centered cubic < primitive cubic < face-centered cubic
E.body-centered cubic < face-centered cubic < primitive cubic
Q:
Which equation represents the number of atoms in a body-centered cubic unit cell?
A.
B.
C.
D.
E.
Q:
The solubility product equilibrium constant, Ksp, of silver bromide is 5.4 10-13 at 298 K.
AgBr(s) Ag+(aq) + Br-(aq)
What is DrG? (R = 8.314 J/Kmol)
A.-3.0 101 kJ/mol
B.-5.87 kJ/mol
C.5.87 kJ/mol
D.3.0 101 kJ/mol
E.7.0 101 kJ/mol
Q:
What is the equilibrium constant for reaction below at 25 C? (R = 8.314 J/Kmol)2 NO(g) + O2(g) 2 NO2(g)given DfG [NO(g)] = +86.6 kJ/mol and DfG [NO2(g)] = +51.2 kJ/mol.A.3.9 10-13B.1.0C.2.6 1012D.1.6 106E.3.8 1028
Q:
All of the following relationships are true EXCEPT
A..
B..
C..
D..
E..
Q:
Calculate DrG for the combustion of benzene at 325 K.2 C6H6() + 15 O2(g) 12 CO2(g) + 6 H2O()Species DfH (kJ/mol) S (J/Kmol)C6H6() 49.0 173.3O2(g) 0 205.1CO2(g) -393.5 213.7H2O() -285.8 67.0A.-6386 kJ/mol-rxnB.-6078 kJ/mol-rxnC.-7251 kJ/mol-rxnD.-8611 kJ/mol-rxnE.+1431 kJ/mol-rxn
Q:
If a chemical reaction is exothermic, but not spontaneous, which of the following must be true?
A.DrG > 0, DrS > 0 and DrH > 0
B.DrG < 0, DrS > 0 and DrH > 0
C.DrG > 0, DrS < 0 and DrH > 0
D.DrG < 0, DrS < 0 and DrH < 0
E.DrG > 0, DrS < 0 and DrH < 0