question

Purpose of evaporation lab

answer

looking at how much energy to pull molecules apart

question

intermolecular forces

answer

hold molecules together - different types include london-disperson, dipole-dipole, hydrogen bonds- and ion-dipole

question

london dispersion forces (LDF)

answer

- type of intermolecular force - everything has these - depend on instantaneous dipole moments (only happen when an electron happens to be in one place at one moment in time) which makes them weak and easy to break - get stronger as the molecule gets stronger since there are more of them (increase in molecular weight = increase in LDF)

question

dipole-dipole

answer

- type of intermolecular force - stronger than LDF because it is a permanent partial negative charge on one spot and a permanent partial positive charge on the other

question

hydrogen bond

answer

- type of intermolecular force - special case of dipole-dipole that occurs between hydrogen & O, F, or N - happens due to hydrogen being REALLY partially positive and O, F, or N being REALLY partially negative - if water didn't have a bent structure that allowed it to have 2 lone pairs (allowing 2 hydrogen bonds), then it would be a gas at room temp - strongest intermolecular force

question

ion-dipole

answer

- type of intermolecular force - occurs between an ion and a polar molecule - stronger than dipole-dipole because in dipole-dipole, each of the molecules are only partially negative or positive whereas in ion-dipole one is totally positive and the other is totally negative so they have a stronger bond to the partial negative and partial positives from the polar molecule

question

order of strengths of intermolecular forces from weakest to strongest

answer

LDF < dipole-dipole< ion-dipole < h-bond

question

alkane

answer

- contain C and H - only intermolecular force present is LDF - the more carbons and hydrogens, the stronger the LDF will be (aka the higher the boiling point will be)

question

alcohols

answer

- contain C, H, and an OH group - intermolecular forces presents are LDF and h-bond

question

the stronger the IMF, the ________ the change in temperature will be because...

answer

smaller, it would take more time/energy to evaporate a substance with stronger intermolecular forces

question

what causes there to be a difference in states

answer

- kinetic energy, intermolecular forces, etc - depends on whats holding one molecule to another

question

what state has the molecules attracted closely but still able to move

answer

liquids

question

what state has the molecules not attracted at all

answer

gas

question

what state has the molecules attracted closely so that there is basically no movement

answer

solid

question

unit cell

answer

- smallest unit that, when stacked repeatedly, makes up the entire crystal - 14 known unit cells - 3 types of cubic unit cells -> simple cubic, body centered, and face centered

question

crystal

answer

- anything with a repeating pattern

question

how do we look at a crystal?

answer

- x ray crystallography - have wave lengths on the size order of an atom

question

simple cubic (primitive) cell

answer

- formation if you have an atom at each of the 8 corners of a perfect cube - only occurs in polonium - corners shared with 8 cubers (each individual corner is 1/8 of an atom) - one net atom in each cube -> weight of unit cell is weight of one atom of polonium

question

coordination number

answer

how many atoms does any 1 atom touch

question

net atoms in simple cubic cell

answer

1

question

coordination number in simple cubic cell

answer

6

question

length of an edge in simple cubic cell

answer

2r

question

volume occupied by atoms in a simple cubic cell

answer

4/3πr³

question

volume of whole cell in a simple cubic cell

answer

8r³

question

body centered cell

answer

- same as simple cubic with an atom on each corner but also has one in the direct center

question

net atoms in a body centered cell

answer

1/8 on each corner = 1 total 1 in the middle = 1 total = 2 net atoms

question

coordination number in a body centered cell

answer

8

question

edge length in a body centered cell

answer

4r/√3

question

volume occupied by atoms in a body centered cell

answer

8/3πr³

question

volume of whole cell in a body centered cell

answer

64r³/3√3

question

face centered cell

answer

- any face of the cell has an atom in the center and at every corner - looks like the 5 side of the dice

question

net atoms in a face centered cell

answer

1/8 on each corner = 1 atom 1/2 on each face = 3 atoms = 4 net atoms

question

coordination number in a face centered cell

answer

12

question

edge length in a face centered cell

answer

4r/√2

question

volume occupied by atoms in a face centered cell

answer

16/3πr³

question

volume of whole cell in a face centered cell

answer

64r³/2√2

question

empirical formula

answer

simplest formula (ratio)

question

NaCl (solid state)

answer

- Cl⁻ forms face centered cell (net 4 atoms) - Na⁺ fills in the holes on the edges and one in the dead center ( 3 ions from edges (1/4 on each edge) and 1 ion from the center = net 4 atoms) - ratio of 4Na⁺ to 4Cl⁻ = empirical formula of NaCl

question

solid state structures for ions

answer

- one ion forms the base cubic unit cell and the other ion fills in the holes -> usually the larger ion

question

octahedral holes

answer

holes on the edges and center of a face centered cell

question

coordination number for an atom in an octahedral hole

answer

6

question

CuCl (solid state)

answer

- Cl⁻ is face centered - Cu⁺ is in the corners but inside the cell

question

tetrahedral holes

answer

- whole atom in the holes -> on the inside corners of the cell

question

coordination number for an atom in a tetrahedral hole

answer

4

question

allotropes

answer

different forms of the same element -> has different properties - i.e. carbon has a bunch of different allotropes

question

most stable allotrope of carbon

answer

graphite

question

graphite

answer

- 2d structure - sheets of fused 6 membrane rings

question

diamond

answer

- every carbon is bonded to 4 carbons - 3 dimensional

question

colligative properties

answer

depend on the # of solute particles in a solution - freezing point depression - boiling point elevation - vapor pressure decrease - osmotic pressure

question

solvent

answer

present in larger quantity in a solution - tends to be water

question

solute

answer

present in smaller quantity in a solution

question

why do we put salt in water for pasta?

answer

raises the boiling point

question

why do we put salt on the road before snow?

answer

lowers the freezing point

question

molarity

answer

(mole solute)/(L solution)

question

molality

answer

(moles solute)/(Kg solvent)

question

elevation of boiling point

answer

adding a solute increases the boiling point of a solvent - this is because it lowers the amount of surface area that the water has to evaporate from because there are also solid particles that are on the surface but won't form a vapor so they ultimately lower the vapor pressure

question

equation for change in boiling point

answer

∆t= (Kbp)(m)(i) i = 1 if you aren't dissolving an ionic compound, if its an ionic compound then its the number of particles the compound breaks into. i.e.: NaCl is 2 because it breaks in Na⁺ and Cl⁻

question

why does have NaCl have a bigger impact on boiling point than C₁₂H₂₂O₁₁?

answer

because NaCl is an ionic compound so it dissociates in water which makes it have twice as many molecules floating around as the other which will stay as one molecule

question

freezing point depression

answer

adding a solute decreases the freezing point of a solvent - this is because there are solid particles on the surface that aren't going to freeze because they are already solid but aren't allowing water particles to freeze so it ultimately takes more energy to get the solution froze

question

equation for freezing point depression

answer

∆t = (Kfp)(m)(i)

question

what is the edge length of a simple cubic unit cell in terms of "r"?

answer

2r

question

if the volume of a sphere is 4/3πr³, what is the volume of a face centered unit cell that is occupied by atoms

answer

16/3πr³

question

the "holes" on the edges of a face centered cubic unit cell are called: a. octahedral holes b. tetrahedral holes c. pentagonal holes d. hexagonal holes

answer

a. octahedral holes

question

the carbons in diamond have what type of hybridization? a. sp b. sp² c. sp³ d. sp^4

answer

c. sp³

question

in the NaCl unit cell, in what type of arrangement or holes are the Cl⁻ ions found? a. simple cubic b. face centered. c. body centered

answer

b. face centered

question

the presence of a solute ______ the frezing point of solution compared to freezing point of the pure solvent a. raises b. lowers c. has no effecent on

answer

b. lowers

question

the solvent in the colligative properties experiment was a. lauric acid b. an unknown c. water

answer

a. lauric acid

question

what is the freezing point of a solution in which 90.0g of glucose, C₆H₁₂O₆, is dissolved in 500 g of water. Kf water = 1.86°C/m MM glucose - 180g/mole a. 1.86°C b. -1.86°C c. 3.72°C d. -3.72°C e. 0.93°C

answer

b. -1.86°C

question

what is the molar mass of a substance if 0.0200g is equal to 3.34 x 10⁻⁶ moles? a. 1.67 x 10⁻⁴ b. 6.68 x 10⁻⁸ c. 5900

answer

c. 5900

question

colligative properties depend on a. the number of solute particles b. the molar mass of the substance

answer

a. the number of solute particles

question

in experiment 1, n-pentane and 1-butanol had almost identical molecular weights but significantly different ∆t values. Explain the difference in the ∆t values of these substances based on their intermolecular forces

answer

- n-pentane has only LDF - 1-butanol had LDF and H-bonds - h-bonds are stronger than LDF so 1-butanol has a smaller ∆t value since it takes more energy to break its intermolecular forces

question

which of the alcohols studied in experiment 1 has the strongest intermolecular forces of attraction? the weakest intermolecular forces? explain

answer

- 1-butanol has the highest molecular weight out of the alcohols which means it has the strongest intermolecular forces - methanol has the lowest molecular weight out of the alcohols which means it has the weakest intermolecular forces - when molecules have identical IMF types you have to look at the molecular weight of the molecules (higher MW = stronger IMF)

question

Which of the two alkanes studied in experiment 1 has the stronger intermolecular forces? the weaker? explain

answer

- n-hexane has the stronger IMF forces because it has a higher molecular weight, which gives it more LDF - by default this makes n-pentane have the weaker IMF since it has the lower molecular weight and less LDF

question

how many carbon atoms are in the diamond unit cell?

answer

8

question

what is the coordination number of each carbon in diamond?

answer

4

question

what is the hybridization of each carbon in diamond?

answer

sp³

question

what is the hybridization of each carbon in graphite?

answer

sp²

question

what is the coordination number of each carbon in graphite?

answer

3

Chem 102 Lab – Exam 1 (exp. 1-3) – Flashcards

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