AnswersLA-Chemistry AElements, Compounds, and Mixtures

Elements, Compounds, and Mixtures — Unit test Answers

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Which statement describes a chemical property of water?

A
It reacts with sodium metal.
B
It has a melting point of 0°C.
C
It has a density of about 1 g/mL.
D
It is clear and colorless.
2
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To explain the photoelectric effect, Albert Einstein linked the photoelectric effect to an idea from which scientist?

A
Heinrich Hertz
B
Isaac Newton
C
Max Planck
D
Thomas Young
3

Which element has an ion that is smaller than an ion of calcium?

A
potassium
B
strontium
C
cesium
D
magnesium
4

What is the electron configuration of chlorine (Cl)?

A
1s22s22p63s23p3
B
1s22s22p63s23p5
C
1s22s22p63s24s23p3
D
1s22s22p63s23p23d3
5

Which is a set of valid quantum numbers?

A
n = 4, l = 4, m = 4
B
n = 1, l = –2, m = 0
C
n = –1, l = 0, m = 0
D
n = 4, l = 3, m = 3
6

The mass number of a chromium atom is 52 and it has 24 protons. How many neutrons does this atom have?

A
24
B
28
C
76
D
80
7

Which is a correct comparison between the modern quantum model and John Dalton’s model of the atom?

A
The modern model is not as widely accepted by scientists as Dalton’s model.
B
The modern model states that atoms of all elements are identical, whereas Dalton’s model does not.
C
The modern model recognizes particles in the atom, whereas Dalton’s model does not.
D
The modern model does not explain emission spectra, whereas Dalton’s model does.
8

When a strip of magnesium metal is touched to a flame, a bright light and a whitish substance are produced. Why is the burning of magnesium considered a chemical change?

A
because the metal reaches a high temperature
B
because the metal begins to melt
C
because a new substance is formed
D
because the metal is malleable
9

An atom of an element is shown by the model.How is this model useful?

Question illustration
A
It shows how electrons are distributed in the shells of an iron atom.
B
It shows how electrons are distributed in the shells of a cobalt atom.
C
It shows how orbitals are distributed in the shells of an iron atom.
D
It shows how orbitals are distributed in the shells of a cobalt atom.
10

A piece of sodium metal can be described as

A
a pure substance and a compound.
B
an impure substance that is reactive.
C
an impure substance that is unreactive.
D
a pure substance and an element.
11

How are isotopes defined?

A
forms of different elements that have the same number of neutrons in each atom
B
forms of different elements that have the same number of protons in each atom
C
forms of the same element that differ in the number of neutrons in each atom
D
forms of the same element that differ in the number of protons in each atom
12

Which statement describes heterogeneous mixtures?

A
They are made up of two or more pure substances that are not chemically bonded together and appear non-uniform.
B
The substances they are composed of can only be separated chemically.
C
The substances they are composed of have fixed ratios between their components.
D
They are made up of two or more pure substances that are chemically bonded together and appear uniform.
13

What is the predicted order of first ionization energies from highest to lowest for lithium (Li), sodium (Na), potassium (K), and rubidium (Rb)?

A
Rb > K > Na > Li
B
K > Rb > Na > Li
C
Li > Na > K > Rb
D
Rb > K > Li > Na
14

Which of these properties is the best one to use for identification of an element?

A
the number of neutrons in the atomic nucleus
B
the number of protons in the atomic nucleus
C
the number of isotopes that are formed by the element
D
the number of charges on ions of the element
15

Which of these is an example of a physical change?

A
sugar, when heated, producing carbon dioxide and water
B
solid ice, when heated, turning into liquid water
C
sodium, when exposed to chlorine, forming sodium chloride
D
aluminum, when heated in air, forming aluminum oxide

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