CEM 142 MSU Final Exam

Does aqueous sugar conduct electricity, why or why not

No, because there are no ions

Does aqueous NaCl conduct electricity?

Yes, because this is an ionic compound (metal/nonmetal)

What is the only IMF present in non polar molecules

London Dispersion Forces

How does electronegativity change in the periodic table

Electronegativity increases from left to right (with the right being most electronegative), and increases from bottom to top (with top most electronegative)

What is present in ALL molecules

LDFs

What is Coulombs Law

unlike charges attract and like charges repel

What is an LDF

temporary fluctuating dipoles

What is the sign of an exothermic reaction

negative

Dipole dipole interactions are present...

only in polar substances

What is the sign of an endothermic reaction

positive

Explain hydrogen bonding and it's rules

Present between 2 molecules:

- the first must contain H covalently bonded to O, N, or F

- the second must have O, N, or F with a lone pair

Are bonds formed or broken during exothermic reactions

formed

If a hydrogen bond is present...

then so are LDFs and dipole dipole interactions

Is energy released or absorbed during exothermic reactions

released

How do you know which molecules has a higher boiling point when comparing 2 molecules

the molecule with stronger IMFs takes more force (energy) to break so it has a higher boiling point

Are bonds formed or broken in endothermic reactions

broken

The attraction between charges particles is caused by...

electronegativity

Is energy released or absorbed during endothermic reactions

absorbed

Does temperature increase or decrease during exothermic reactions

increase

(heat goes out of the system and the surroundings get hotter)

Does temperature increase or decrease during endothermic reactions

decrease

(heat goes into the system and the surroundings get colder)

When are IMFs present in water

solid and liquid phase

What is the first law of thermodynamics?

Energy cannot be created or destroyed

What is a state function

depends only on the initial and final states, does not depends on the path taken

ex: the elevation of a camp site on a mountain is a state function because it is independent of that path taken to reach it

Enthalpy is a ______ function

state

What is the sign of enthalpy?

delta H

What is the sign of entropy?

delta S

What does it mean if delta S is negative

there is more order

What does it mean if delta S is positive

There is more disorder or chaos, more number of arrangements

The more possible arrangements, the _______ the probability of that state

higher

Systems are more likely to be in a ________ state

mixed

Why are systems more likely to be in a mixed state?

There are a great number of arrangements in this state, therefore entropy of the universe would be increasing

Why will energy always transfer from a hot block to a cold block

The energy will transfer from the hot block to the cold block until the two are at the same temperature because this allows for the greatest number of arrangements

In what phase is entropy (number of arrangements) the highest

gas

Explain the order of entropy from most to least

gas>liquid>solid

How can something be in a solid state if the entropy of the system decreases?

the entropy of the surroundings increases which means the total entropy of the universe is increasing

What is the delta S of the system if a cup of water is on a hot plate but the plate is below 273K?

The delta S of the system will be less than 0 because the number of arrangements decreases as the water freezes

What is the delta H of the previous system?

Heat is leaving the system since bonds are being formed, so the reaction is exothermic (-)

When 2 molecules are being compared, how do you tell which has the highest delta H of vaporization?

The one with the strongest IMFs because these require more energy to break

Delta S of the surroundings depends on what?

Temperature

If temperature is high, entropy change is...

low

If temperature is low, entropy change is...

high

What is the free energy equation?

deltaG= deltaH - (T)(deltaS)

Temperature is always _____ in the free energy equation

positive

Definition of a solution

homogenous mixture of 2 or more components

Definition of solute

thing being dissolved

Definition of solvent

Thing doing the dissolving

You make a solution of 100 grams of H2O and 5 grams of NaCl. What is the resulting mass?

Exactly 105 grams

You make a solution of 100mL of water and 5mL of ethanol. What is the resulting volume and why?

Between 100-105mL because volumes are not additive. Molecules can get closer together when they're mixed because the molecules can pack in tightly

How do you make a solution

Using a volumetric flask, add the solute to the flask and fill up the required volume with solvent, then read at the bottom of meniscus

What are the 7 strong acids

HCl, HNO3, H2SO4, HBr, HI, HCIO3, HCIO4

What are the 8 strong bases

LiOH, NaOH, KOH, Ca(OH)2, RbOH, Sr(OH)2, CsOH, Ba(OH)2

What are the metals and nonmetals

How do you tell if a molecule will dissociate into ions

If it's a metal paired with a nonmetal

Definition of immiscible

solute and solvent do not mix (like oil and water)

Definition of miscible

solute and solvent mix and form a solution; once mixed they do not unmix

Define saturated

no more solute will dissolve

Define unsaturated

if you add more solute it will dissolve

What is Molarity

mol/liter

What is percent mass?

same as parts per hundred

A 10% by mass solution has 10g of solute per 100 g solution

What is parts per millions (ppm)

1ppm solution has 1g of solute per 10^6 gram of solution

(same as 1ug microgram of solute per gram of solution)

What is parts per billion (ppb)

1ppb solution has 1g of solute per 10^9 gram of solution

(same as 1 nanogram ng solute per gram solution)

1 ppm =

1 mg/L

1 ppb=

1 ug/L

If you add water to a concentrated solution, does the concentration (amount of moles) change?

No, the amount of moles in the concentrated solution= the amount of moles in the dilute solution

What is the dilution formula

M1V1=M2V2

If interactions between particles in the solute are overcome, is this exothermic or endothermic

endothermic because bonds are being broken

If interactions between some particles in the solvent are overcome, is this exothermic or endothermic

endothermic because bonds are being broken

If interactions are formed between the solute and solvent, is this exothermic or endothermic

exothermic because bonds are being formed

The more CH groups a substance has...

the less soluble it is in water

What interactions exist within ionic compounds

ion-ion

Does delta G tell you anything about the temperature

No

When CaCl2 is added to water the temperature rises. What is the "system" in this scenario

the ions in solution and associated water molecules

When CaCl2 is added to water the temperature rises. What is the "surrounding" in this scenario

The non associated water molecules

If the temperature decreases during a reaction, what does this mean for the strength of bonds within the interaction and why?

This means that the solvent-solvent and solute-solute interactions are strongest. We can deduce this because if the temperature decreases, then the reaction is endothermic. This tells us that bonds are being broken, which tells us the breaking of the bonds is the strongest

If the temperature increases during a reaction, what does this mean fro the strength of bonds within the interaction and why?

This means that the solvent-solute interactions are strongest. We can deduce this because if the temperature increases, then the reaction is exothermic. This tells us that bonds are being formed, which tells us the forming of the bonds is the strongest

How do you find molarity from a given volume and mass?

Take the mass over the volume, (if the volume isn't in liters, convert it to liters), then multiply that by the molar mass to get the answer

If you're given the molarity, how do you find the concentration of one atom in the compound?

Take the molarity and multiply it by the individual moles given in the name of the compound (ex: CaCl2. The moles in Ca are 1 (because no number by it), and the moles in Cl2 are 2 (because 2 is by Cl2)

How do you find the total ion concentration?

Take the already calculated molarity, and multiply it by the amount of ions the molecule will split into over the total moles of the molecule (which will generally be 1)

Which thermodynamic factor is affected by temperature

delta S

Why don't oil and water mix?

The entropy of the system is higher in the unmixed state because non-polar molecules cause water molecules to cluster around them

What happens when a hydrocarbon enters water?

Water forms a cage (clathrate) around the hydrocarbon molecule

Definition of hydrophilic

water loving

Definition of hydrophobic

water fearing

Definition of amphipathic molecules

Have both polar and non polar parts

What happens when an amphipathic molecule enters water

the polar part interacts with water through H-bonds, and the non polar part causes the water to form a clathrate around it

What will amphipathic molecules do in water

form micelles

Definition of a micelle

organized clusters of amphipathic molecules

What part of the micelle is hydrophilic

The water loving head

What part of the micelle is hydrophobic

The water fearing tail

Solubility of gases ______ as temperature increases. Why?

Decreases; because the entropy of the gas would decrease as there would be fewer possible arrangements, so if T increases and delta S increases, delta G would become more positive

Definition of an alloy

mixture of metals

What are the two types of alloys?

substitute and interstitial

Define substitute alloy

if atoms are of a similar size, the solute atoms substitute for the solvent atoms

Define interstitial alloy

If the solute is smaller, the atoms can sit in holes within the structure

What is the Arrhenius Acid-Base model?

Says that an acid dissolves in water to always give H+, and a base dissolves in water to always give OH-. This model completely ignores the role of water and therefore isn't used that much

Does H+ exist in aqueous solution?

No, it's generally transferred to water which is why the Arrhenius Acid-Base model isn't a good representation

When given the equation HCl + NaOH <--> NaCl + H2O, what would be the detailed ionic equation?

H + Cl + Na+ OH <----> Na + Cl + H2O

When given the equation HCl + NaOH <--> NaCl + H2O, what would be the spectator ions?

Na+ and Cl-

Definition of spectator ions

species that don't change throughout the reaction are spectator ions

When given the equation HCl + NaOH <--> NaCl + H2O, what is the net ionic equation?

H + OH <----> H2O