Chemistry001A Chapter 3A Homework

Microwave ovens emit microwave energy with a wavelength of 12.8 cm. What is the energy of exactly one photon of this microwave radiation?

(3x10^8 m/s)/(.128m)=2343750000/s E=2343750000x6.63x10^-34 E=1.5530x10^-24

The Frequency of the middle C note on a piano is 21.63 Hz. What is the wavelength of this note in centimeters? The speed of sound in air is 343.06 m/s

343.06/261.63uA=1.31 meters 1.31x100=131.124 centimeters.

Minimum frequency of light needed to eject electrons from a metal is call the threshold frequency,Vo. a)Find the minimum energy needed to eject electrons from a metal with a threshold frequency of 5.13x10^14. b)With what maximum kinetic energy will electrons be ejected when this metal is exposed to light with a wavelength of lambda 255nm?

A) E=h*v E=6.603x10^-34*5.13x10^14 E=3.387*10^-19 B) E=h*(C/wl) E=6.6032*10^-34*(3*10^8/2.55*10^-7) E=7.768*10^-19 7.768x10^-19-3.387x10^-19=4.38x10^-19

For a hydrogen like atom, classify the electron transition by whether they absorb or emit light Ignoring sign, which transition is associated with the greatest energy change?

Absorption: n=1 to n=3, n=3 to n=5 Emission: n=2 to n=1, n=3 to n=2. n=1 to n=3 because of electrostatic force

The mass of an electrno is 9.11x10^-31kg. What is the uncertainty in the position of an electron moving at 8.00x10^6 m/s with an uncertainty of deltav=.01x10^6 m/s?

Deltax>h/4piDeltaV 6.626x10^-34/4(pi)(9.11x10^-31kg)(.01x10^6m/s)=5.79x10^-9m

A certain shade of blue has a frequency of 7.2x10^14 Hz. What is the energy of exactly one photon of light

E=HF E=6.63×10−34 J·s.x 7.2x10^14 E=4.7x10^-19

Consider a single photon with a wavelength, nu, and energy. What is the wavelength, frequency, and energy of a pulse of light containing 100 of these photons

E=h*(c/wl) E=100*h*(c/wl) E= same wavelength, nu, and 100E

How many photons are produced in a laser pulse of .396 J at 629nm?

E=h*(c/wl) E=6.603x10^-34*(3.10^8/6.29e^-7) E=3.160e^-19 J/photon .396J/3.160e^-19=1.25x10^18

A watt is a unit of energy per unit time, and one watt(w) is equal to one joule per second a 40 w incandescent light-bulb produces about 7% of its energy as visible light. Assuming that the light has an average wavelength of 510 nm, calculate how many such photons are emitted per second

E=h*(c/wl) E=HxC/5.1e^-7 E=3.884e^-19 j/photon*2.6 J/s E=7.2088x10^18 photons/second

The series in the He spectrum that corresponds to the set of transitions where the electron falls from a higher level to the nf = 4 state is called the Pickering series, an important series in solar astronomy. Calculate the Pickering series wavelength associated with the excited state ni = 9. En=(-2.18x10^-18)Z^2/n^2

En=(-2.18x10^-18J)z^2(1/9^2-1/4^2) =4.37x10^19 J Lambda=hc/E=(6.626x10^-34)(3.00x10^8)/(4.37x10^-19) =4.54x10^-7

A metal foil has a threshold frequency of 5.45x10^14 Hz. Which of the colors of visible light have enough energy to eject electrons from this metal?

Lambda=c/nu (3.00x10^8 m/s)/(5.45x10^14/s) =5.50x10^-7 m=550nm=green light (green, Blue Indigo, violet)

To resolve an object in an electron microscope, the wavelength of the electrons must be close to the diameter of the object. What kinetic energy must the electrons have in order to resolve a protein molecule that is 4.00 nm in diameter? Take the mass of an electron to be 9.11× 10-31 kg.

Lambda=h/m v v=h/m lambda= 6.626x10^-34/(9.11x10^-31)(4.10^-9)=182000 m/s K.E=1/2mv^2 =1/2(0.11x10^-31kg)(182000m/s)^2=1.51x10^-20 J

Electromagnetic radiation

Long wavelength to short wavelength: Radio, Microwave, Infrared, Vissible, Ultraviolet, X-ray, Gamma ray

Frequency of incident radiation(10^15)(s^-1): 2.00,2.5,3,3.5,4 Kinetic energy ejected(10^-19)(J): 5.9,9.21,12.52,15.84,19.15

Slope:Rise/run=Planck constant=6.62x10^-34 Threshold: when x=0. Because need to past zero in order for photoelectric effect to work. - Joules doesn't work. Need positive joules.

A certain rifle bullet has a mass of 6.21 g. Calculate the de Broglie wavelength of the bullet traveling at 1505 miles per hour. Physical constants can be found here.

V=1505 mi/hr x 1.609km/1mi x 10^3 m/1km x 1 h/3600 s =672.7 m/s Lambda=h/mv =6.626x10^-34/(6.21x10^-3)(672.7)=1.59x10^-34

a)Consider a 2630-lb automobile clocked by law-enforcement radar at a speed of 85.5 mph (miles/hour). If the position of the car is known to within 5.0 feet at the time of the measurement, what is the uncertainty in the velocity of the car? b)If the speed limit is 75 mph, could the driver of the car reasonably evade a speeding ticket by invoking the Heisenberg uncertainty principle?

a) Deltax=5.0 ft x .3048 m/ 1 ft=1.524 m m=2630 lbx45.59g/1lbx1kg/1000g=1193 kg Delta V=6.626x10^-34/4(pi)(1193)(1.524)=6.5x10^-38mi/hr b) 85.5+ - 6.5x10^-38 mi/hr . Difference not enough to not get yourself the speed ticket.

Electromangetic spectrum ROYGBIV:

red=microwave violet=gamma ray