Recent content by stacker

2.4 Interactions of X-Rays and Gamma Rays in Matter X-rays and gamma rays are both high-energy photons. In the energy range 1–100 keV, these photons are usually called X-rays and above 100 keV they are usually called gamma rays. Some authors use the term ‘gamma rays’ to refer to any photon of...

Homework Statement An atomic spectrum contains a line with a wavelength centered at 460 nm. Careful measurements show the line is really spread out between 459 and 461 nm. Estimate the lifetime of the excited state that produced this line. Homework Equations Change in Frequency =...

Yes but it doesn't say how you get wavelength. Although E = hf and f = c/wavelength. E = h(c/wavelength). In which case what is E?

You actually think I went through all this trouble of logging onto this forum, copying down the question, and explaining why I don't know how to solve it before googling the equation...

Homework Statement Photons of energy 12 eV are incident on a metal. It is found that current flows from the metal until a stopping potential of 8.0 V is applied. If the wavelength of the incident photons is doubled, what is the maximum kinetic energy of the ejected electrons? Homework...

Homework Statement If it takes a fish 0.19s to perform evasive action, at what minimum height must it spot the pelican to escape? [Suppose a pelican starts its dive from a height of 15.9 m and cannot change its path once committed] If it takes a fish 0.19s to perform evasive action, at...

Dipole Moment! Ok I'm very tired because I've spent the past 50 minutes trying to figure out a problem that should take only 5. Someone please just take 2 minutes of your time to save me 20 more minutes. THis is a simple problem yet I cannot do it on my own, without my textbook and with what...

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Homework Statement What is the bond order of B22- Homework Equations (Number of bonding electrons - number of antibonding electron)/2 The Attempt at a Solution (3-0)/2 = 1.5, which is wrong. What's going on?

Ok but what is the variable "V" in my problem in relation to the equation from wikipedia: Delta H = V + .5 B + IE - EA - U

I plugged in +567.4 and it was wrong. What is going on? What does that variable V equal to in relation to my problem in the equation that you gave me from wiki?

Homework Statement What is the lattice energy of KI? Given the information below. Heat of formation for KI = -328 kJ/mol Heat of sublimation for K = 89.20 kJ/mol Ionization energy for K = 419 kJ/mol Bond dissociation energy for I2 = 149 kJ/mol Electron affinity for I = - 295...

Homework Statement What is the lattice energy of LiI? Given the information below. Heat of formation for LiI = -270 kJ/mol Heat of sublimation for Li = 159.40 kJ/mol Ionization energy for Li = 520 kJ/mol Bond dissociation energy for I2 = 149 kJ/mol Electron affinity for I = -...

Yes that's the right answer! But I'm still having trouble understanding why, in terms of units, you can multiply the last step by (6.02 x 10^23 atoms/mol) and still get units of (kJ/mol). When did the unit of "atoms" appear? Reflection: I made the mistake of not properly converting the Si-Units...

Homework Statement What is the energy (in kJ/mol) of infrared radiation that has a frequency of 1.614 x 107 MHz? Homework Equations E = nhv The Attempt at a Solution 3 x 6.63 x 10^-34 (J x s) multiplied by 1.614 x 10^7 (MHz) multiplied by (10^6 Hz/1 MHz) multiplied by (1 kJ/ 1000J) =...