Chem exam 1 review

Which of the following statements is/are true regarding the uncertainty principle?

- It is impossible to simultaneously know the exact position and exact momentum for any object. - it determines a minimum value of uncertainty (h/4pi) - the more we know about velocity, the less we know about position and vice versa - the larger the mass, the less uncertainty

Which isotope has 35 protons, 35 electrons, and 46 neutrons?

81 Br 35

Which of the following about sodium atoms (Na) is NOT correct?

All sodium atoms have 11 neutrons

what is the equation that demonstrates the relationship between wavelength and frequency?

C = lambda*nu (speed of light = wavelength*frequency)

what are the orbital shapes associated with the l value?

l=0 s shape l=1 p shape l=2 d shape l=3 f shape 1=4 g shape

what is the equation for the wavelength of a moving particle?

lambda = h/mv (wavelength = planck's constant/mass*velocity)

The size of an atomic orbital is determined by which quantum number?

n

An electron in a hydrogen atom could undergo any of the transitions listed below, by emitting light. Which transition would give light of the shortest wavelength?

n = 4 to n = 1 Photons with shorter wavelengths have more energy than those with longer wavelengths. n = 1 is the lowest energy level, the energy increases as n increases. A transition from n = 4 to n = 1 will release more energy than any other option given.

How many values of mℓ are allowed for an electron in a 5 f subshell?

7, n=5, l=3, ml=-3,-2,-1,0,1,2,3

How many values of mℓ are allowed for an electron in a 2 s subshell?

1, n=2, l=0, ml=0

Which of the following is a valid description of atomic number?

1. Atomic number is equal to the number of electrons in a neutral atom. 2. Atomic number is equal to the number of protons in an atom. 3. Atomic number is equal to the positive charge of an atoms nucleus.

What is the highest energy photon that can be absorbed by a ground-state hydrogen atom without causing ionization?

2.18 × 10−18 J

How many values of the quantum number ℓ are possible when n = 3?

3, for n=3, l=0,1,2

A new element has two isotopes, one with a mass of 40.0 amu and the other with a mass of 42.0 amu. The atomic weight is 40.50 g/mol. Pick the true statement.

40.5 g/mol = 40(x) + 42(1-x) solve for x determine which is more abundant

A hypothetical element has two main isotopes. One has a mass of 43 amu and the other has a mass of 45 amu. If the atomic weight of this element is 43.56 amu, what is the percent abundance of the 45 amu isotope?

43.56 amu = 45(x) + 43(1-x) solve for x

What is the subshell notation and the number of orbitals that can have the quantum numbers n = 5, ℓ = 2?

5d, 5

what is the equation for the energy of a photon?

Ep=h*nu + 1/2mv^2(energy of a photon = work function + KE

T/F The Balmer series of lines for the hydrogen atom are found only in the visible region of the spectrum.

False: all visible light is in the Balmer series, but not all of the Balmer series is visible light

T/F The longer the wavelength of light, the higher is its frequency.

False: wavelength and frequency have an inverse relationship, as wavelength increases, frequency decreases and vice versa.

Which of the following is true about spin pairing?

It brings about a small attraction between electrons in the same orbital

Which of the following statements best summarizes the Planck theory of light?

Light contains bundles of energy; the shorter the wavelength of light, the higher the energy of the bundles

In the 20th century, quantum mechanics addressed the failures of classical mechanics by introducing the concept of wave-particle duality. Why was classical mechanics able to explain the world just fine up until then?

Macroscopic objects can be modeled purely as particles because their wavelength is so small compared to their scale that it can be neglected for most purposes and still give a good description of their behavior.

A lawyer who received a speeding ticket argues that because of the Heisenberg Uncertainty Principle the radar reading is uncertain. The judge, who happens to have a science degree, rules against the lawyer. Which of the following statements is true?

The judge is correct because the car is so massive that the uncertainty in speed is very small.

Consider two particles: a proton and a shotgun pellet. The proton (1.7 × 10−27 kg) is moving at speeds roughly half the speed of light while the shotgun pellet (2 × 10−3 kg) is moving at about 250 m/s. Both have 1% uncertainty in their velocities. Which has the greater uncertainty in position?

The photon: it has a significantly smaller mass

Which of the following statements about the spectral lines of hydrogen is true according to the Bohr model?

They have frequencies which depend directly on the differences in energy between energy levels.

T/F If one electron in an atom is excited but does not have enough energy to escape, the energy of the excited electron must have one of a set of quantized values.

True

The quantum mechanical approach to atomic structure permits the calculation of

a region about the nucleus in which an electron of specified energy will probably be found.

One of the first radar devices developed during World War II used microwave radiation of a wavelength that triggers the rotation of water molecules. This was an unfortunate coincidence because

absorption of microwave radiation by water in the atmosphere interferes with the detection of intended objects.

The Bohr theory of the hydrogen atom

accounts for the fact that light of only certain wavelengths is given off when a hydrogen atom is excited.

Classically the energy contained in electromagnetic radiation is proportional to the (amplitude, frequency, wavelength), whereas in quantum mechanics it is proportional to the (amplitude, frequency, wavelength)

amplitude, frequency

For which would the de Broglie wavelength be significant: an electron or a golf ball

an electron

what is the equation to calculate the wavelength of the radiation emitted by a hydrogen atom when the hydrogen makes the transition from one energy level to another?

deltaE = 2.178E-18 (1/nf^2-1/ni^2) deltaE = h*nu

what is the equation for the change in energy?

deltaEp=n*h*nu (change in energy = number of photons*planck's constant*frequency)

How would you explain what happens when Ep<work function of a metal?

electrons will not pop off

How would you explain what happens when Ep>work function of a metal?

electrons will pop off and eject from the metal

How would you explain what happens when Ep=work function of a metal?

electrons will pop off but will not eject from the metal

When a given molecule absorbs a photon of UV light, at higher wavelengths it moves electrons to () states, but at lower wavelengths it causes ()

excited, ionization

A line spectrum is to an element as what is to a person?

fingerprint

When a given molecule absorbs a photon of visible light it moves electrons from () states to () states

ground (low energy) to excited (high energy)

When a given molecule absorbs a photon of x-ray radiation it causes

ionization

When a given molecule absorbs a photon of gamma radiation it causes () as well as ()

ionization, breaking of covalent bonds

How many subshells are there in the shell with n = 3?

n=3, l=0,1,2, 3s 3p and 3d

When a given molecule absorbs a photon of radio waves it causes

nuclear spin

In quantum mechanics the intensity of a light beam is interpreted as the

number of photons passing a point per second times the energy of each photon

The azimuthal (subsidiary) quantum number provides us with information about which characteristic of an electron bound in an atom?

orbital shape

The mass number of an atom is the number of protons in the nucleus

plus the number of neutrons.

Exchange in energy between matter and radiation occurs in

quanta (photons)

What is the correct order of increasing frequency?

radio waves, infrared radiation, visible light, ultraviolet radiation

When a given molecule absorbs a photon of microwave radiation it causes molecules to

rotate

The lines in an atomic line emission spectrum are due to

the movement of electrons from higher energy states to lower energy states in atoms

The lines in an atomic line absorption spectrum are due to

the movement of electrons from lower energy states to higher energy states in atoms

According to the results of Einstein's photoelectric effect experiment

there is a threshold frequency; at higher frequency, photoelectrons are produced while at lower frequency they are not

When a given molecule absorbs a photon of infrared it causes molecules to

vibrate

what is the equation to find the average atomic mass of an element?

weighted average = (mass of isotope 1*abundance) + (mass of isotope 2*abundance) etc