B is the central atom and is an exception to the octet rule, requiring only 6 electrons. Since there are no lone pairs of electrons, the B-H and B-F bonds spread out from one another, resulting in trigonal planar geometry. The bonds are polar in the direction of F, so the molecule is polar.
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Which of the following choices could be an isomer of a compound with an empirical formula of C₂H₆O₂?
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C₄H₉O₄
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CHO
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C₄H₁₂O₄
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CH₂O
CONCEPT
Accuracy is defined as how close a measured value comes to a _____ value.
-
core
-
common
-
fixed
-
true
CONCEPT
Apple pie would be an example of a(n) __________.
-
element
-
pure substance
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heterogeneous mixture
-
homogenous mixture
CONCEPT
How many electrons are in a neutral Si atom?
-
14
-
3
-
7
-
28
RATIONALE
The atomic number of silicon (Si) is 14, and it tells us that a neutral Si atom contains 14 protons in its nucleus and 14 electrons outside its nucleus.
Which of these would a chemist most likely study?
-
how rain affects statues
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where earthquakes tend to occur
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why airplanes are able to fly
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why monkeys have tails
RATIONALE
This is about the composition, properties, and interaction of matter, so it would be something a chemist studies. In this case, chemicals in rain are interacting with chemicals in the statues.
CONCEPT
What is the correct name for CoCl₂∙6H₂O?
-
cobalt chloride hydrate
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cobalt chlorine water
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cobalt(II) chloride hexahydrate
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cobalt chloride
CONCEPT
How many bonding electrons are in the Lewis structure of PCl₃?
-
4
-
6
-
2
-
5
CONCEPT
Which of the following has more core electrons than it does valence electrons?
-
beryllium
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carbon
-
sulfur
-
oxygen
CONCEPT
Which of the following is a metalloid?
-
P
-
Zn
-
La
-
Si
RATIONALE
Metalloids include B, Si, Ge, As, Sb, Te, and At.
A 200.0 cg block at 55⁰F has a volume of 4.14 cm³.
Which answer choice represents BOTH the correct temperature of the block in Kelvin AND the correct density of the block in g/cm³?
-
286 ⁰K; 4.83 x 10⁻¹ g/cm³
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286 ⁰K; 2.07 g/cm³
-
-260 ⁰K; 2.07 x 10⁻¹ g/cm³
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12.8 ⁰K; 4.83 x 10⁻¹ g/cm³
RATIONALE
Convert ⁰F to ⁰K by first converting ⁰F to ⁰C, then adding 273.15. Since d = m/v, both mass and volume are needed (in grams and cubic centimeters, respectively, since that is the desired density unit in the question). Convert cg to g to determine mass.
CONCEPT
Which of the following correctly expresses the value of 2.0 x 
in decimal notation AND in the SI unit for electric current?
-
0.002 V
-
2,000 A
-
2,000 V
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0.002 A
RATIONALE
This number has a negative exponent. So, to convert to decimal notation, you move the decimal to the left 3 spaces. This yields 0.002. The SI unit for electric current is amperes (A).
Which of the following is polar and has trigonal planar molecular geometry?
-
H₂O
-
BHF₂
-
LiCl
-
H₂
RATIONALE
B is the central atom and is an exception to the octet rule, requiring only 6 electrons. Since there are no lone pairs of electrons, the B-H and B-F bonds spread out from one another, resulting in trigonal planar geometry. The bonds are polar in the direction of F, so the molecule is polar.
CONCEPT
To which of the following atoms is it likely easiest to add an electron?
-
O
-
He
-
N
-
Sr
CONCEPT
Which of the following particles are found in an atom’s nucleus?
-
electron
-
proton
-
gamma particle
-
beta particle
CONCEPT
Which of these is more likely to be a gas at room temperature?
-
LiO₂
-
Ca₃P₂
-
NaCl
-
SO₂
RATIONALE
This compound contains covalent bonds, so it is much more likely to be a gas at room temperature.
CONCEPT
The scientific method requires the use of information that is based on observation or experimentation.
This type of information is called which of the following?
-
Correlational evidence
-
Qualitative evidence
-
Critical thinking
-
Empirical evidence
CONCEPT
To which atom(s) was Bohr able to successfully apply his model?
-
all atoms
-
hydrogen
-
no atoms
-
helium
CONCEPT
Calculate the following using proper units and significant figures: (5.57 m / 0.63 m) – (1.11 m x 0.82 m)
-
7.9311 m²
-
7.9 m²
-
7.931 m
-
7.93 m
RATIONALE
First perform the division operations in parentheses. The first operation will result in 2 significant figures (sig figs), since 0.63 contains 2 sig figs, and the number with the fewest sig figs determines the number of sig figs in the answer in division problems. This same reasoning applies to the operation in the second set of parentheses, which will result in 2 sig figs since 0.82 contains 2 sig figs. The result, then, is 8.8412698 m² + 0.9102 m² = 7.9310698 m², which rounds to 7.9 m², since subtraction rules requires rounding the sum or to the same number of decimal places as the measurement with the fewest decimal places.
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