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A Ch6-10 Chemistry Exam 3 > Ch6-8 > Flashcards

Ch6-8 Flashcards

1
Q

Endothermic

A

Energy is gained

Q is positive

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2
Q

Exothermic

A

Energy is lost to its surroundings

Q is negative

-q

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3
Q

Internal energy E

A

Some of the kinetic and potential energies of all the components of the system

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4
Q

🔼E

A

Change in E = E(final)-E(initial)

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5
Q

Doing work on a system is a way to add to its?

A

Internal energy

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6
Q

Doing work on a gas causes the temperature of the gas to?

A

Rise

Internal energy increases

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7
Q

The total increase in the energy of a closed system is?

A

The sum of the work done on (w) and any other energy gained (q)

🔼E=q+w

Change in Energy= energy gained+ work
done on it

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8
Q

The energy changes of a close system and its surroundings are?

A

Equal in Magnitude but opposite in sign
So their sum=0

🔼E(system) + 🔼E(surroundings)=0

🔼Energy= work done + energy gained

🔼=change in

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9
Q

When work is done by a system on its surroundings, the internal energy of the system?

A

Decreases.

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10
Q

Covalent means

A

Co =shared
Valent = valence electrons

Covalent bonds means shared electrons in the outer shell like H2

A pair of electrons shared (bond)

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11
Q

Metallic bonds form ?

A

A sea of mobile electrons that move freely among all the atoms in a metallic solid
(Delocalized)

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12
Q

Electron mobility makes metals what?

A

Good conductors of heat and electric electricity

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13
Q

Electron sharing of nonmetals and metalloids

A

Covalent - Shared Electrons

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14
Q

Electron sharing of metals and nonmetals

A

Ionic - transferred electrons

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15
Q

Electron sharing of metals

A

Metallic - delocalized (a “sea” of mobile electrons that move freely among all the atoms in a metallic solid)

Metals = good conductors or heat & electr

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16
Q

Ionic compounds that contain polyatomic ions have 2 types of bonds which are?

A

Covalent and ionic

Covalent electrostatic attractions &
Ionic electrostatic attractions between ions

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17
Q

Exceptions to the Octet rule happen a lot with which elements??

A

H, Be, & B

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18
Q

Compounds with fewer than eight valence electrons around an atom are referred to as?

A

Electron deficient compounds

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19
Q

Gilbert N Lewis

A

1916 American chemist proposed that atoms formed chemical bonds by sharing electrons

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20
Q

Octet rule

A

Atoms of most main group elements lose, gain, or share electrons so that each atom has eight valence electrons

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21
Q

Exceptions to the octet rule

A

A duet- Hydrogen shares only a single pair of bonding electrons

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22
Q

Lewis Dot Chart

A
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23
Q

Left to right
Bottom to top
Top to bottom
Bottom left to bottom right

A

Lewis structure dot placement

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24
Q

Examples of incomplete octets due to odd numbers of valence electrons in those molecules include?

A

NO
NO2

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25
A single bond is?
A pair of electrons SHARED between two atoms
26
Lone pairs are?
Electron pairs that are not involved in bonding formation, appear as pairs of dots on one atom
27
Bonding electrons count ?
Bonding electrons only count as 1 electron towards each valence # required but when trying to complete an octet, those same bonds count as 2 for each atom
28
Lewis structure of ionic compounds
29
Lewis structure of Cation & anion with more than a plus one charge
30
HCL—->
H+ + Cl- both aq to show dissolved in water
31
Polar covalent bonds travel
From the positive ion to the negative one like a battery ends
32
Bond polarity
Dipole starts at the positive end and travels to the negative end and functions as 1 dipole
33
The positive ion gets what end of the dipole?
Positive gets the beginning of the dipole
34
The negative end gets what end of the dipole?
The arrow points to the negative ion with the arrow ending on the negative side
35
A nonpolar bond is
Between the same atom because it has the same charge so there’s no distribution of charges
36
HCl is what type of bond? NaCl is what type of bond?
HCl is polar covalent uneven charged distribution NaCl is ionic-complete transfer of electron
37
What indicates the direction of polarity?
The arrow with the + and its tail and its tail starts at the positive atom
38
What type of bond transfers electrons?
Ionic
39
What type of bond shares electrons?
Covalent
40
What type of bond has an even distribution of electrons when it’s a bond between the same atom like CL2?
NonPolar covalent Non opposites
41
The change in energy of ionic bonds is
2.0
42
What can electronegativity be used to determine?
The types of bonds between two atoms Starts at bottom & Increases UP to RIGHT
43
Bonds made up of the SAME ELEMENT are what type? H-H O-O or F-F
PURE or NONPOLAR COVALENT Electrons are share EQUALLY between the 2 atoms
44
Atoms of elements with similar electron negativities: O-Cl, N-O form what kind of bond?
Polar Covalent 2 non-metals (polar makes it 2 diff elements) Electrons are SHARED UNEQUALLY and based on their electronegativity, we can determine this ratio of shared electrons
45
Atoms of elements with widely different electron negativities: Na-Cl, K-Br form what type of bond?
Ionic bond
46
How can you tell an ionic bond from a polar covalent bond?
If the electronegativity has a difference of 1.9 or more, its ionic (large difference) Group 1 elements with group 8 elements = ionic bonds
47
What type of bond is formed by the compound HCl?
K is 0.8 & F is 4.0 4-0.8 =3.2 which is an ionic bond
48
What type of bond is formed by the compound KF?
K is 0.8 & F is 4.0 4-0.8 =3.2 which is an ionic bond bc the difference between their electronegativity is larger than 1.9
49
Bonds in Ethane, 2 types: C2H6 H H H—C—C—H H H
Bond between 2 Carbons - pure covalent Electronegativity of Carbon is 2.5–itself=0 6 Carbon to Hydrogen Bonds Carbon 2.5–2.1(hydrogen)=0.4 POLAR COVALENT -small# but not 0 In a structure like Ethane, we can have 2 types of Bonds
50
Pure covalent vs polar covalent
Pure Covalent is the same atom sharing e- Polar covalent (polar opposites) different elements Covalent (shared valence electrons)
51
What is the difference between electron negativity and electron affinity?
Electron Affinity- an isolated atoms ability to gain an additional electron (1 atom can gain an electron) Electronegativity - ability of an atom within a chemical bond to attract electrons towards itself. (Shared E-ability to be more attracted to 1 elements than the other)
52
Steps to drawing Lewis structures
1. Skeleton - Letters Symmetrically placed Least electronegative= center (least electrons) H & F are usually on the ENDS 2. Count total Valence Electrons (group #) —- add e- for negative charge —- subtract e- for a positive charge 3. Draw Single BONDS to connect atoms (a dash or 2electrons between 2 atoms) —-Draw dots around all atoms so there are 8 electrons on each-octet rule (H:duet rule) 4. if too many e-, try another type of bond
53
When the difference between- how many electrons we need to put in our Lewis structure & how many electrons we did put- is 2, how should we proceed?
Erase 4 dots and put 1 double bond. That takes away 4 and adds 2 so now we are 2 short of our number before that was over by 2
54
Method to find the number of valence electrons needed to satisfy the Octet rule?
Find the # of valence electrons needed to satisfy the octet rule: (# of non-H atoms*8) +(#of H atoms*2)= =total # of electrons needed Find the number of electrons involved in a covalent bond: (#needed-#available)=#bonding electrons Ex. PCl3 4 atoms *8e- = 32e- needed P= 5 available, Cl=7available*3=21 32e- needed - 26e- available = 6 6 extra e-/2 per bond=3 bonds
55
How do you find the number of bonding electrons in a covalent bond? DOES NOT WORK FOR THE OCTET EXCEPTIONS LIKE ONES WITH HYDROGEN
DOES NOT WORK FOR THE OCTET EXCEPTIONS LIKE ONES WITH HYDROGEN -Take the # of electrons available according to the GROUP# on the periodic table and subtract that # from the total # needed to satisfy the octet rule and that will give you the number of extra electrons for bonding, divide that number by 2 and that gives you the # of bonds needed!
56
Formal Charge, on an Atom in a Lewis Structure, Formula:
# of valence electrons in an atom—total # of non bonding electrons—1/2 total # of bonding electrons #VE—#Non-BE—1/2(#BE) **calculation must be done for each element in the diagram separately (Used to determine best structure to use) Most likely to form, most plausible
57
What must the formal charge of an atom in a low structure add up to for: —a neutral molecule, —a cation, & —an anion
Neutral Molecule = formal charge = 0 Cation = must add up to the + charge Anion = must add up to the - charge
58
The use of 2 or more Lewis structures to represent a molecule is called
Resonance
59
What is a reasonance structure?
1 of 2 or more Lewis Structures needed to accurately represent a single molecule due to different ways to draw the same structure
60
How do you connect 2 resonance structures?
Double headed arrow
61
Octet Rule Exceptions - less than 8 electrons on the central atom
Incomplete Octet H—Be—H
62
Exception Odd Electron Molecules
NO & NO2 uses double bonds NO2 - In both resonance structures, nitrogen gets a double bond to 1 O and single bond to the other plus 1 electron - each O totals 8 electron counting each bond as 2
63
Expanded Octet
SF6- drawn exactly how you would expect. A single bond to each F and 6 single electrons around each F
64
Bond dissociation energy
The entropy change required to break a particular bond in one mole of gaseous molecules Measure of stability 🔼H=(bond E of reactants)-(bond E of products)
65
🔼H = (Sum of bond Energy of reactants)—(Sum of bond Energy of Products)
=(Total Energy Input)—(Total Energy Released) (Bonds Broken)-(Bonds Formed) =measure of stability in KJ/mole
66
The harder it is to break apart a bond
The more stable it is
67
Step 1 in calculating Bond Dissociation Energy is?
DRAW LEWIS STRUCTURES FIRST !! DRAW LEWIS STRUCTURES FIRST!! To show bonds! H2(g) + F2(g) —> 2HF(g) H—H + F—F(with 6 each)—> H—F(with 6) Bonds broken =H—H (436kj) F—F (155kj) Bonds formed = H—F(567kj) H—F(567kj) [436+155]-[567+567]= -543kj=🔼H Using chart to see what bonds equal
68
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A Ch6-10 Chemistry Exam 3 (2 decks)

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