52. a process in which heat moves into the system is called
a) endothermic
b) exothermic
c) entropic
d) spontaneous
53. the measurement of heat flow is called
a) chromatography
b) stoichiometry
c) spectroscopy
d) calorimetry
54. which of these represents a net gain of energy by a closed system?
a) heat moves into the system
b) the system loses mass to the surroundings
c) the system expands into the surroundings
d) the temperature of the surroundings increases
55. iron (fe) has a specific heat capacity of 0.450 j/g·°c. it takes ______ of heat to raise the temperature of 50.0 g of fe from 25.0 °c.
a) 113 j
b) 5.62 kj
c) 563 j
d) 4.44 kj
56. when comparing possible lewis structures using a formal charge analysis, negative formal charge should be placed
a) on a metal
b) on the atom with the highest electronegativity
c) on the atom with the lowest electronegativity
d) on the atom with the highest atomic number
57. the electron configuration for rn is
a) kr5s²4d¹⁰
b) kr4s²3d¹⁰
c) ar4s²4d¹⁰
d) kr5s²4d¹⁰
58. overlap of s atomic orbitals form which of these sets of molecular orbitals?
a) σ and π
b) π and π*
c) σ and σ*
d) σ* and π*
59. in terms of molecular orbital theory, as bond order increases, bond strength ______ and bond length ______.
a) increases, increases
b) decreases, decreases
c) increases, decreases
d) decreases, increases
60. which of these molecules would you expect to be polar?
a) c₂h₂
b) ch₄
c) ch₂cl₂
d) ccl₄

Question

Accepted Answer

### Question 52
# Brief Explanations:
To solve this, we recall the definitions: Endothermic processes absorb heat (heat moves into the system), Exothermic releases heat, Entropic relates to entropy, Spontaneous is about reaction spontaneity. So the correct term for heat moving into the system is Endothermic.
# Answer:
A) Endothermic

### Question 53
# Brief Explanations:
Chromatography separates mixtures, Stoichiometry is about reaction ratios, Spectroscopy studies light - matter interaction, Calorimetry measures heat flow. So the measurement of heat flow is Calorimetry.
# Answer:
D) Calorimetry

### Question 54
# Brief Explanations:
- Option A: Heat moving into the system means the system gains energy (heat is a form of energy), so this shows a net gain.
- Option B: Losing mass to surroundings doesn't directly relate to energy gain (mass and energy are related but this isn't a net energy gain in the context of heat/energy transfer here).
- Option C: Expanding into surroundings is about volume change, not net energy gain.
- Option D: Temperature increase of surroundings means the system is losing energy (heat is leaving the system), not gaining. So the answer is A.
# Answer:
A) Heat moves into the system

### Question 55
# Explanation:
## Step 1: Recall the specific heat formula
The formula for heat $ q $ is $ q = mc\Delta T $, where $ m $ is mass, $ c $ is specific heat, and $ \Delta T $ is change in temperature.
## Step 2: Identify the values
Given $ m = 50.0\ g $, $ c = 0.450\ J/g\cdot^{\circ}C $, $ \Delta T=25.0^{\circ}C $ (assuming the temperature change is from initial to $ 25.0^{\circ}C $, since the problem says "to raise the temperature of 50.0 g of Fe to $ 25.0^{\circ}C $" - we assume the initial temperature is such that $ \Delta T = 25.0^{\circ}C $ or the change is $ 25.0^{\circ}C $).
## Step 3: Calculate $ q $
Substitute into the formula: $ q=(50.0\ g)\times(0.450\ J/g\cdot^{\circ}C)\times(25.0^{\circ}C) $
$ q = 50\times0.45\times25=50\times11.25 = 562.5\ J\approx563\ J $ (or convert to kJ: $ 563\ J=0.563\ kJ $, but looking at options, 563 J is option C)
# Answer:
C) 563 J

### Question 56
# Brief Explanations:
In Lewis structure formal charge analysis, negative formal charge should be placed on the atom with the highest electronegativity because more electronegative atoms attract electrons more strongly and are more stable with negative charge. Lower electronegativity atoms (metals) tend to have positive formal charges, atomic number is not the main factor for formal charge placement. So the answer is B.
# Answer:
B) On the atom with the highest electronegativity

### Question 57
# Brief Explanations:
Rn (Radon) is a noble gas. The electron configuration of Rn is $[Xe]6s^{2}4f^{14}5d^{10}6p^{6}$. But looking at the options, the correct noble gas configuration for Rn - related (maybe a typo, but for Rn, the electron configuration is $[Xe]4f^{14}5d^{10}6s^{2}6p^{6}$, and among the options, option C: $[Xe]5s^{2}4d^{10}$ is incorrect, option A: $[Kr]5s^{2}4d^{10}$ is for a different element, option B: $[Kr]4d^{10}5s^{2}$ is also incorrect. Wait, maybe the question is about Rn - but the options seem a bit off. Wait, maybe it's a typo and the element is Ru (Ruthenium)? No, Rn is Radon. Wait, the correct electron configuration for Rn is $[Xe]6s^{2}4f^{14}5d^{10}6p^{6}$. But among the given options, if we assume a mistake and maybe the question is about a different element, but based on the options, the correct electron configuration for Rn (if we consider the noble gas core) is $[Xe]6s^{2}4f^{14}5d^{10}6p^{6}$, but the closest option in terms of noble gas core is option C: $[Xe]5s^{2}4d^{10}$ is wrong. Wait, maybe the question is misprinted. But if we go by the options, the correct electron configuration for Rn is $[Xe]6s^{2}4f^{14}5d^{10}6p^{6}$, but the options given:

Option A: $[Kr]5s^{2}4d^{10}$ - Kr is krypton, this is for a different element.

Option B: $[Kr]4d^{10}5s^{2}$ - also not Rn.

Option C: $[Xe]5s^{2}4d^{10}$ - Xe is xenon, no.

Option D: $[Xe]5s^{2}4d^{10}$ - same as C? Wait, maybe the question is about a different element. But if we assume that the question is about Rn, and there is a typo, and the correct option is C? No, I think there is a mistake in the question options. But based on the noble gas configuration, Rn has $[Xe]$ as the core, so the correct option should be related to $[Xe]$. But among the options, the only one with $[Xe]$ is option C: $[Xe]5s^{2}4d^{10}$ (even though it's incorrect for Rn, maybe it's a typo and the element is a transition metal). But if we have to choose, maybe the intended answer is C. Wait, no, maybe the question is about Rn, and the options are wrong. But I will go with option C as the closest in terms of noble gas core (Xe) among the options.

# Answer:
C) $[Xe]5s^{2}4d^{10}$ (Note: There might be a typo in the question, but based on the given options, this is the best choice)

### Question 58
# Brief Explanations:
When atomic orbitals overlap, they form bonding ($\sigma$ and $\pi$) and antibonding ($\sigma^{*}$ and $\pi^{*}$) molecular orbitals. The overlap of atomic orbitals forms $\sigma$ and $\sigma^{*}$ (for single bond - like overlap) or $\pi$ and $\pi^{*}$, but the basic set formed by overlap of atomic orbitals includes $\sigma$ and $\sigma^{*}$ (and $\pi$ and $\pi^{*}$ for multiple bonds). But the question is "Overlap of atomic orbitals form which of these sets of molecular orbitals?". The correct sets are $\sigma$ and $\sigma^{*}$ (and $\pi$ and $\pi^{*}$ but among the options, option C: $\sigma$ and $\sigma^{*}$ is correct as $\sigma$ is a type of molecular orbital formed by overlap, and $\sigma^{*}$ is the antibonding counterpart.

Option A: $\sigma$ and $\pi$ - $\pi$ is also formed by overlap, but the question is about the set formed by overlap, and the antibonding orbitals are also part of the set. But the options:

Option A: $\sigma$ and $\pi$ - these are bonding orbitals, but the overlap also forms antibonding.

Option B: $\pi$ and $\pi^{*}$ - only $\pi$ - type.

Option C: $\sigma$ and $\sigma^{*}$ - $\sigma$ (bonding) and $\sigma^{*}$ (antibonding) formed by overlap.

Option D: $\sigma^{*}$ and $\pi^{*}$ - only antibonding.

So the correct answer is C.
# Answer:
C) $\sigma$ and $\sigma^{*}$

### Question 59
# Brief Explanations:
In molecular orbital theory, bond order is related to bond strength and bond length. As bond order increases, the number of bonding interactions increases, so bond strength increases (stronger bond) and bond length decreases (shorter bond, since more bonding electrons pull the atoms closer). So bond strength increases and bond length decreases.
# Answer:
C) Increases, Decreases

### Question 60
# Brief Explanations:
- A polar molecule has a net dipole moment (unequal distribution of electron density).
- Option A: $C_2H_4$ (ethene) is non - polar (symmetrical, planar, dipole moments cancel).
- Option B: $CH_4$ (methane) is non - polar (tetrahedral symmetry, dipole moments cancel).
- Option C: $CH_2Cl_2$ (dichloromethane) - the $C - H$ and $C - Cl$ bonds have different electronegativities. The molecule is tetrahedral but not symmetrical (two $Cl$ and two $H$ atoms), so there is a net dipole moment (polar).
- Option D: $CCl_4$ (carbon tetrachloride) is non - polar (tetrahedral symmetry, dipole moments of $C - Cl$ bonds cancel). So the polar molecule is $CH_2Cl_2$.
# Answer:
C) $CH_2Cl_2$

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