# 6.1 Electromagnetic energy  (Page 10/27)

 Page 10 / 27

## Key equations

• c = λν
• $E=h\nu =\phantom{\rule{0.2em}{0ex}}\frac{hc}{\lambda },$ where h = 6.626 $×$ 10 −34 J s
• $\phantom{\rule{0.2em}{0ex}}\frac{1}{\lambda }\phantom{\rule{0.2em}{0ex}}={R}_{\infty }\left(\phantom{\rule{0.2em}{0ex}}\frac{1}{{n}_{1}^{2}}\phantom{\rule{0.2em}{0ex}}-\phantom{\rule{0.2em}{0ex}}\frac{1}{{n}_{2}^{2}}\phantom{\rule{0.2em}{0ex}}\right)$

## Chemistry end of chapter exercises

The light produced by a red neon sign is due to the emission of light by excited neon atoms. Qualitatively describe the spectrum produced by passing light from a neon lamp through a prism.

The spectrum consists of colored lines, at least one of which (probably the brightest) is red.

An FM radio station found at 103.1 on the FM dial broadcasts at a frequency of 1.031 $×$ 10 8 s −1 (103.1 MHz). What is the wavelength of these radio waves in meters?

FM-95, an FM radio station, broadcasts at a frequency of 9.51 $×$ 10 7 s −1 (95.1 MHz). What is the wavelength of these radio waves in meters?

3.15 m

A bright violet line occurs at 435.8 nm in the emission spectrum of mercury vapor. What amount of energy, in joules, must be released by an electron in a mercury atom to produce a photon of this light?

Light with a wavelength of 614.5 nm looks orange. What is the energy, in joules, per photon of this orange light? What is the energy in eV (1 eV = 1.602 $×$ 10 −19 J)?

3.233 $×$ 10 −19 J; 2.018 eV

Heated lithium atoms emit photons of light with an energy of 2.961 $×$ 10 −19 J. Calculate the frequency and wavelength of one of these photons. What is the total energy in 1 mole of these photons? What is the color of the emitted light?

A photon of light produced by a surgical laser has an energy of 3.027 $×$ 10 −19 J. Calculate the frequency and wavelength of the photon. What is the total energy in 1 mole of photons? What is the color of the emitted light?

ν = 4.568 $×$ 10 14 s; λ = 656.3 nm; Energy mol −1 = 1.823 $×$ 10 5 J mol −1 ; red

When rubidium ions are heated to a high temperature, two lines are observed in its line spectrum at wavelengths (a) 7.9 $×$ 10 −7 m and (b) 4.2 $×$ 10 −7 m. What are the frequencies of the two lines? What color do we see when we heat a rubidium compound?

The emission spectrum of cesium contains two lines whose frequencies are (a) 3.45 $×$ 10 14 Hz and (b) 6.53 $×$ 10 14 Hz. What are the wavelengths and energies per photon of the two lines? What color are the lines?

(a) λ = 8.69 $×$ 10 −7 m; E = 2.29 $×$ 10 −19 J; (b) λ = 4.59 $×$ 10 −7 m; E = 4.33 $×$ 10 −19 J; The color of (a) is red; (b) is blue.

Photons of infrared radiation are responsible for much of the warmth we feel when holding our hands before a fire. These photons will also warm other objects. How many infrared photons with a wavelength of 1.5 $×$ 10 −6 m must be absorbed by the water to warm a cup of water (175 g) from 25.0 °C to 40 °C?

One of the radiographic devices used in a dentist's office emits an X-ray of wavelength 2.090 $×$ 10 −11 m. What is the energy, in joules, and frequency of this X-ray?

E = 9.502 $×$ 10 −15 J; ν = 1.434 $×$ 10 19 s −1

The eyes of certain reptiles pass a single visual signal to the brain when the visual receptors are struck by photons of a wavelength of 850 nm. If a total energy of 3.15 $×$ 10 −14 J is required to trip the signal, what is the minimum number of photons that must strike the receptor?

RGB color television and computer displays use cathode ray tubes that produce colors by mixing red, green, and blue light. If we look at the screen with a magnifying glass, we can see individual dots turn on and off as the colors change. Using a spectrum of visible light, determine the approximate wavelength of each of these colors. What is the frequency and energy of a photon of each of these colors?

Red: 660 nm; 4.54 $×$ 10 14 Hz; 3.01 $×$ 10 −19 J. Green: 520 nm; 5.77 $×$ 10 14 Hz; 3.82 $×$ 10 −19 J. Blue: 440 nm; 6.81 $×$ 10 14 Hz; 4.51 $×$ 10 −19 J. Somewhat different numbers are also possible.

(a) The laser on a Blu-ray player has a wavelength of 405 nm. In what region of the electromagnetic spectrum is this radiation? What is its frequency?

(b) A Blu-ray laser has a power of 5 milliwatts (1 watt = 1 J s −1 ). How many photons of light are produced by the laser in 1 hour?

(c) The ideal resolution of a player using a laser (such as a Blu-ray player), which determines how close together data can be stored on a compact disk, is determined using the following formula: Resolution = 0.60( λ /NA), where λ is the wavelength of the laser and NA is the numerical aperture. Numerical aperture is a measure of the size of the spot of light on the disk; the larger the NA, the smaller the spot. In a typical Blu-ray system, NA = 0.95. If the 405-nm laser is used in a Blu-ray player, what is the closest that information can be stored on a Blu-ray disk?

(d) The data density of a Blu-ray disk using a 405-nm laser is 1.5 $×$ 10 7 bits mm −2 . Disks have an outside diameter of 120 mm and a hole of 15-mm diameter. How many data bits can be contained on the disk? If a Blu-ray disk can hold 9,400,000 pages of text, how many data bits are needed for a typed page? (Hint: Determine the area of the disk that is available to hold data. The area inside a circle is given by A = πr 2 , where the radius r is one-half of the diameter.)

What is the threshold frequency for sodium metal if a photon with frequency 6.66 $×$ 10 14 s −1 ejects an electron with 7.74 $×$ 10 −20 J kinetic energy? Will the photoelectric effect be observed if sodium is exposed to orange light?

5.49 $×$ 10 14 s −1 ; no

Why does carbonic acid don't react with metals
Why does carbonic acid don't react with metal
Some metals will react depending on their Standard Electrode Potential. Carbonic acid is a very weak acid (i.e. a low hydrogen ion concentration) so the rate of reaction is very low.
Paul
sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
a sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
an object of weight 10N immersed in a liquid displaces a quantity of d liquid.if d liquid displaced weights 6N.determine d up thrust of the object
how human discover earth is not flat
We don't fall off. If set off in any direction in a straight line and keep going. You'll end up back where you started.
earth is spherical
Unique
Also, every other planet is spherical as that is the most energy efficient shape. gravity pulls equally on all areas. Sphere.
what is an ion
an atom that loses or gains an electron. Atoms normally have the same number of protons and electrons, therefore there is no charge as each + cancels out each -. When an atom loses an electron, it has more protons that electrons. Therefore the ion is called positive.
When an atom gains electrons it has more of them than protons. Therefore the ion is negative. You cannot change the number of protons as this results in a different element.
Gaining or losing electrons is based around the octet rule. 8 electrons in the outer shell is the most stable electron configuration (for the first three rows in the periodic table. After that it gets confusing so don't worry) So all atoms want to achieve this configuration.
Wat is chemical bonding
how to determine the number of atoms and the mass of zirconium, silicon, and oxygen found in 0.3384 mol of zircon4
what is a catalyst
A substance that speeds up the rate of a given reaction but does not react with any reactants
Brandon
something that speeds up a chemical reaction without being used up itself. It lowers the activation energy
something that speed up a chemical reaction without its self been used
Zainab
Faraday's first law of electrolysis state that...
the mass of a substance librated during electrolysis is directly proportional to the quantity of electricity passing through the electrolyte
Zainab
nice
Owolabi
greeaat
Abdul
another question
Owolabi
ys
Abdul
good
olanrewaju
gud one pls write it mathematically
Lekan
How can ionic bonds dissociate in aqueous solution
Because of the polarity of both ionic compounds and water the ionic compound will dissolve as "like dissolves like", and the molecule forms bonds with the water.
Claud
are all aqueous solutions water contained?
blossom
No, but a lot are.
Claud
it dissociate when d metal is combined wit oxygen
Lekan
I wanna understand more about isomers
Isomers are essentially the same molecules of one particular substance, except with different bonding points along the molecule. if you want a better example, look up xylene, p-xylene, and m-xylene. isomers are more for organic chemistry
Aaron
what is catenation
The property of carbon to form long chain with other atom!
Lareb
hydrocarbons can be classified as..1.Aliphatic compounds 2.cyclic compounds.under aliphatic compounds there are two types saturated hydrocarbons(alkanes) and unsaturated hydrocarbons(alkenes and alkynes).
thanks but i have also heard of aromatic hydrocarbons
emmanuel
so am kinda confused
emmanuel
how
Emmanuel
hydrocarbons are classified into 2 namely: aliphatic compound and aromatic compound
Mgbachi
aliphatic compound and aromatic compound
Mgbachi
hello i have big problems in understanding organic chemistry
what are the main types of hydrocarbon
emmanuel
I'm not exactly sure what you mean by 'main types' but I think you should be talking about aliphatic and cyclic hydrocarbons
blossom
What's the difference?
Claud
what is the difference between atomic theory and modern atomic theory
Yakubu
Or are you referring to the types being alkane, alkene and alkyne? alkane - hydrocarbon molecule with only single bonds alkene - hydrocarbon molecule with at least 1 double bond alkyne - hydrocarbon with at least 1 triple bond. alkane least reactive, alkene in the middle alkynes most reactive
I think that is what he is talking about
IBRAHIM