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Chem > EXAM 2 Chem > Flashcards

EXAM 2 Chem Flashcards

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1
Q

what will happen earn 2 identical waves that are out of phase when combin

A

zero amplitude

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2
Q

most significant conclusion to be drawn from the observation of the photoelectric effect

A

the light is contained in discrete packages of energy

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3
Q

ground state of electron confg of oxygen

A

1s2 2s2 2p4

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4
Q

How many atoms of uranium are there in 3.02 moles of this substance?

A

1.82 × 1024 atoms

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5
Q 
The mineral zircon contains the following elements in the mass proportions indicated:
49.8% Zr
15.3% Si
34.9% O
What is the empirical formula of zircon?
A

ZrSiO4

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6
Q

According to the Bohr model of the atom, when does the energy of an electron in an atom decrease?

A

When the charge of the nucleus increases or the quantum number n decreases

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7
Q

What is the difference between a 2s orbital and a 2p orbital?

A

They have different angular momentum quantum numbers.

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8
Q

Which of the following statements correctly describes an observation of the photoelectric effect?

A

There is a frequency of light below which no electrons are emitted.

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9
Q

How many moles of ethanol are contained in 57.38 grams of ethanol (C2H5OH)?

A

1.246 moles ethanol

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10
Q

Which label is most appropriate for the horizontal scale of this diagram of the electromagnetic spectrum?

A

Increasing wavelength

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11
Q

What does the energy of the work-function value represent?

A

The amount of energy required to overcome the attractive forces between an electron and the bulk metal.

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12
Q

What is electron affinity?

A

The energy change that occurs when an atom gains an electron.

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13
Q

What is the ground state electron configuration for fluorine?

A

1s22s22p5

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14
Q

Which of these waves has the greatest amplitude?

A

C the large waves

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15
Q

How does the size of the cation compare to its corresponding atom?

A

The cation is smaller

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16
Q

What is the relationship between acetic acid (C2H4O2 ) and glyceraldehyde (C3H6O3 )?

A

Both molecules have the same empirical formula

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17
Q

Electronegativity describes the ability of an atom to attract additional electron density to itself. Electronegativity would not help predict:

A

Solubility of a substance in water.

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18
Q

Which of the following is a consequence of the Heisenberg uncertainty principle?

A

The exact path taken by an electron cannot be determined, only its probable path.

19
Q

Which of the following is the least electronegative element and the most electronegative element, respectively?

A

francium, fluorine

20
Q

When the mass percent of each element making up an unknown compound is given, what other information is needed to determine the empirical formula?

A

the molar mass of each element

21
Q

Why does a sheet of paper appear white?

A

because it reflects all wavelengths of visible light

22
Q

Which of the following is a correct statement of Hund’s Rule?

A

Electrons will occupy separate degenerate orbitals and maintain parallel spins before pairing up.

23
Q

For a given element, how does the size of the anion compare to the size of the atom?

A

larger

24
Q

What happens to the size of an atom when it loses an electron?

A

The atom becomes smaller

25
Q

How many molecules of carbon dioxide are found in 2.50 moles of carbon dioxide?

A

1.51 × 1024 molecules

26
Q

What is the electron configuration of the oxide ion (O2− )

A

1s22s22p6

27
Q

What is the ground state electron configuration for boron

A

1s22s22p1

28
Q

Which of the following is the general periodic trend for increasing electron affinity

A

up and right

29
Q

How many atoms are contained in 1.00 mole of water?

A

18.0 × 1023 atoms

30
Q

An unknown pesticide is made up of 18.28% carbon, 0.77% hydrogen, and 80.95% chlorine. What is the empirical formula of the pesticide?

A

C2HCl3

31
Q

What happens to the ionization energy as the size of the nucleus increases

A

It increases.

32
Q

How many moles are represented by 3.75 × 1021 atoms of iron?

A

6.23 × 10−3 moles Fe

33
Q

when two waves combine what do they make

A

larger one

34
Q

Under what circumstances does the Bohr model fail to make accurate predictions of an atom’s spectra?

A

When the number of electrons in the atom is greater than 1

35
Q

An atom of helium has a de Broglie wavelength of 4.3 × 10−12 meter. What is its velocity?

A

2.3 × 104 m / s

36
Q

What is the reason that conversion from grams to moles is useful?

A

Balanced chemical reactions relate to numbers of reactant molecules, not to masses of reactant molecules

37
Q

What is the maximum number of electrons that may be found in a 3p energy sublevel?

A

6

38
Q

Why is it possible to predict the momentum of a golf ball much more accurately than that of an electron?

A

The energy of the photons used to observe a golf ball is small compared to the energy of the golf ball.

39
Q

To what does the “ultraviolet catastrophe” refer?

A

The catastrophic implications for turn-of-the-century physics of the absence of ultraviolet light in the emission spectrum of a black body.

40
Q

Which of the following best describes incandescence?

A

The electromagnetic radiation emitted by an object when it is heated.

41
Q

In 1900, which of the following did Max Planck propose in order to solve the ultraviolet catastrophe?

A

He proposed that in a heated body, a discrete amount of energy is absorbed by the multiple oscillators.

42
Q

A great deal of time and effort has been put into trying to locate the electrons in an atom. Why is it important to understand where the electrons are?

A

Knowing where the electrons are allows prediction and understanding of how atoms come together to form molecules.

43
Q

What is the most significant conclusion to be drawn from the observations of the photoelectric effect?

A

That light is contained in discrete packages of energy.

Chem (4 decks)

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