EXAM 2 Chem

Question 1

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

Answer 1

zero amplitude

Question 2

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

Answer 2

the light is contained in discrete packages of energy

Question 3

ground state of electron confg of oxygen

Answer 3

1s2 2s2 2p4

Question 4

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

Answer 4

1.82 × 1024 atoms

Question 5

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?

Answer 5

ZrSiO4

Question 6

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

Answer 6

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

Question 7

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

Answer 7

They have different angular momentum quantum numbers.

Question 8

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

Answer 8

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

Question 9

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

Answer 9

1.246 moles ethanol

Question 10

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

Answer 10

Increasing wavelength

Question 11

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

Answer 11

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

Question 12

What is electron affinity?

Answer 12

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

Question 13

What is the ground state electron configuration for fluorine?

Answer 13

1s22s22p5

Question 14

Which of these waves has the greatest amplitude?

Answer 14

C the large waves

Question 15

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

Answer 15

The cation is smaller

Question 16

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

Answer 16

Both molecules have the same empirical formula

Question 17

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

Answer 17

Solubility of a substance in water.

Question 18

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

Answer 18

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

Question 19

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

Answer 19

francium, fluorine

Question 20

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

Answer 20

the molar mass of each element

Question 21

Why does a sheet of paper appear white?

Answer 21

because it reflects all wavelengths of visible light

Question 22

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

Answer 22

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

Question 23

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

Answer 23

larger

Question 24

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

Answer 24

The atom becomes smaller

Question 25

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

Answer 25

1.51 × 1024 molecules

Question 26

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

Answer 26

1s22s22p6

Question 27

What is the ground state electron configuration for boron

Answer 27

1s22s22p1

Question 28

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

Answer 28

up and right

Question 29

How many atoms are contained in 1.00 mole of water?

Answer 29

18.0 × 1023 atoms

Question 30

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?

Answer 30

C2HCl3

Question 31

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

Answer 31

It increases.

Question 32

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

Answer 32

6.23 × 10−3 moles Fe

Question 33

when two waves combine what do they make

Answer 33

larger one

Question 34

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

Answer 34

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

Question 35

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

Answer 35

2.3 × 104 m / s

Question 36

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

Answer 36

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

Question 37

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

Answer 37

6

Question 38

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

Answer 38

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

Question 39

To what does the “ultraviolet catastrophe” refer?

Answer 39

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

Question 40

Which of the following best describes incandescence?

Answer 40

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

Question 41

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

Answer 41

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

Question 42

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?

Answer 42

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

Question 43

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

Answer 43

That light is contained in discrete packages of energy.