Honors General Chemistry II : FINAL EXAM REVIEW

Water

In aqueous solutions, what is typically considered to be the solvent?

Solubility

This is the amount of the substance that will dissolve in a given amount of solvent.

Entropy

A measure of energy randomization or energy dispersal in a system.

Yes

Does entropy increase when we have a solute and solvent interact with each other?

Solvent–solute interactions:

The interactions between a solvent particle and a solute particle.

Solvent–solvent interactions:

The interactions between a solvent particle and another solvent particle.

Solute–solute interactions:

The interactions between a solute particle and another solute particle.

Yes

In Solvent–solute interactions > Solute–solute interactions & solvent–solvent interactions, does a solution generally form?

Yes

In Solvent–solute interactions = Solute–solute interactions & solvent–solvent interactions, does a solution generally form?

It may or may not form depending on the concentration

In Solvent–solute interactions < Solute–solute interactions & solvent–solvent interactions, does a solution generally form?

It is exothermic

When we have a mixture between the solvent and the solute, what does that typically mean for the reaction?

The solution will be endothermic as this will take energy to break apart

When we want to break a solvent into parts, what does that typically mean for the reaction?

The solution will be endothermic as this will take energy to break apart

When we want to break a solute into parts, what does that typically mean for the reaction?

Δ𝐻_soln ≈ 0

The sum of the endothermic terms is approximately equal in magnitude to the exothermic term, then this happens because energy is constant, but the increasing entropy will instead drive the formation of the solution.

Δ𝐻_soln > 0

If the sum of the endothermic terms is greater in magnitude than the exothermic term, then Δ𝐻_soln is positive and the solution process is endothermic. Entropy can still drive it to form a solution, but it may be risky if the energy is too large.

Δ𝐻_soln < 0

If the sum of the endothermic terms is smaller in magnitude than the exothermic term, then Δ𝐻_soln is negative and the solution process is exothermic. Energy will still drive it to form a reaction.

The heat of hydration

This is the enthalpy change that occurs when one mole of the gaseous solute ions is dissolved in water.

𝛥𝐻_solute < 𝛥𝐻_hydration

This is typically exothermic, as the amount of energy needed to separate the solute molecules is less than the energy given off when hydrated

𝛥𝐻_solute > 𝛥𝐻_hydration

This is typically endothermic, as the amount of energy needed to separate the solute molecules is more than the energy given off when hydrated

𝛥𝐻_solute = 𝛥𝐻_hydration

The amount of energy needed to separate the solute molecules is equal to the energy given off when hydrated

Increasing temperature

How can the solubility increase for solids?

They can decrease the solubility of gases (if you think about it pressure is being released once temperature increases)

What can temperature do the the solubility of gases?

Increase it

When we increase the pressure of gases, what will that do the solubility?

Henry’s Law

What is the formula used to describe the solubility of gases?

Since molarity is dependent on volume, it can easily be affected by temperature change.

Why do we prefer to use molality instead of molarity in solutions?

There will be a positive deviation, as the solute particles will allow the solvent to vaporize more (dilute solution)

When Solvent–solute interactions < Solute–solute interactions & solvent–solvent interactions, how can we compare that with the ideal vapor pressure?

There will be a negative deviation, as the solute particles will NOT allow the solvent to vaporize more (concentrated solution)- so the solution vapor pressure will decrease

When Solvent–solute interactions > Solute–solute interactions & solvent–solvent interactions, how can we compare that with the ideal vapor pressure?

This will lower the vapor pressure

When we add a nonvolatile solute to a solution, what does that do the vapor pressure?

The melting point will decrease- Boiling point will increase

With the nonvolatile solute still in the solution, how will that affect the melting point? Boiling point?

Osmosis is meant to draw the solvent to itself (particles go from a high to low concentration.)

What is the goal of osmosis?

We can use osmotic pressure to oppose this process

How can we prevent the solvent from drawing itself in an osmotic tube?

Van Hoff’s Factor

The ratio of moles of particles in solution to moles of formula units dissolved is called the.. (seen in electrolytes when dissolved in water)

The orientation and the temperature of the reaction.

When we want to increase the rate of a reaction, what are a few main factors to watch out for?

The REACTANTS!! (products yes, but we will be focusing more on reactants)

When we look at chemical kinetics, what is our main focus?

The stochiometry of the concentrations over the time along with it being negative IF its a reactant. This all varies

When we want to find the average rate of reaction, what can we base it off of?

Find the average based on the concentration and time- IGNORE THE STOCHIOMETRY!

What if we just want to find the single rate of reaction of either a reactant or product?

independent

In a zero order reaction, is the rate of reaction dependent or independent on the concentration of the reactant?

Hydrogen bonds

What type of intermolecular force could possible increase the solubility of a compound in water?

If one side has a positive dipole and the other has a negative dipole.

How can dipole-dipole interactions cause an increase in solubility?

When the amount of reactant actually avaliable for reaction is not affected by changes in the overall quantity of reactant. (like sublimation)

When can zero order reactions occur?

First-Order reaction

This order reaction has the rate of the reaction be directly proportional to the concentration of the reactant, which causes the rate to slow down as the reaction proceeds due to the decrease of reactants.

Second-Order reaction

The rate of reaction is more proportional to the square of the concentration of the reactant, making it more sensitive to the reactant concentration.

First Order

When we look at the rate of a concentration and its concentration, say that the concentration doubles, causing the rate to double too- what type of order is that?

Zero-order

When we look at the rate of a concentration and its concentration, say that the concentration doubles, but the rate doesn’t change- what type of order is that?

Second-Order

When we look at the rate of a concentration and its concentration, say that the concentration doubles, and the rate quadruples- what type of order is that?

The sum of the exponents of the order of the reactions.

Overall Order

Integrated Rate Law

This rate law shows us the relationship between the concentrations of the reactants and the time.

The graph would be a straight line (negative)- The first order equation is constant at this concentration

When we plot ln[A]_t and the time based on the first reaction, what does the graph look like?

The graph would have a (positive) straight line- The second order equation is constant at this concentration

When we plot 1/[A]_t and time based on the second order, what does the line look like? Why?

The graph would be a straight (negative) line

When we plot the Zero Order with the concentration [A]_t and time, what does the graph look like?

The time required for the concentration of a reactant to fall to one half of its initial value

Half Life (t_1/2)

t_1/2 is independent of the initial concentration

When we work with a first order reaction, what does the equation look like?

It is constant

Through the definition of half life in the first order equation, what does that mean for the half life itself?

The integrated rate law depends on the initial concentration

In the half life equation for a second-order reaction, what does the integrated rate law look like?

It will get longer

When the concentration decreases for a second order reaction, what does that mean for the half life?

The zero order half life depends on the initial concentration, but the 2 are directly proportional

When we look at the zero order half life equation, what can we infer?

The half life gets shorter

What happens to the half life if we tried to decrease the concentration in a zero order reaction?

Arrhenius equation

This equation shows the relationship between the rate constant (k) and the temperature in kelvin.

Activation Energy (E_a)

An energy barrier or hump that must be surmounted for the reactants to be transformed into products.

Activated Complex (transition state)

This is to get from the reactant to the product and the barrier that the reactant must overcome.

The molecules will have enough energy to overcome the activation energy.

When we increase the temperature, what does that do to the molecules and the activation barrier?

Reaction Mechanism

The series of individual chemical steps by which an overall chemical reaction occurs.

Elementary Step

Each step in a reaction mechanism that occurs as they are written and represents the exact species that are colliding in the reaction.

Reaction Intermediate

Forms in one elementary step and is consumed in another.

The reactants and its stoichiometry.

When we look at elementary steps to determine the rate law, what do we look at?

Through the slow reaction.

When we have a slow and a fast elementary step, how can we determine the reaction mechanism?

2 energy/transition states

When we draw out energy diagrams for 2-step mechanisms, what do we have to be sure to include?

The slow mechanism has the higher activation energy

What is typically to be expected of reaction mechanisms?

Determine the reaction intermediate and find the rate as how you would normally solve for it.

When we work with a reaction that has an elementary step with an initial fast step, how can we work that out?

Catalyst

This can increase reaction rates and don’t show up in the overall reaction

They can decrease them (lower them)

What can catalysts do to transition states?

Dynamic equilibrium

This is when the reaction goes on at an equal rate.

Right

Let’s say you add more reactants to a dynamic equilibrium reaction, where does the reaction shift?

Left

Let’s say you add more products to a dynamic equilibrium reaction, where does the reaction shift?

Wherever there isn’t that many moles of gas particles

Let’s say we decrease the volume in a reaction, which direction will the equilibrium reaction shift?

The reaction will shift to the greater number of moles of gas particles

Let’s say we increase the volume in a reaction, which direction will the equilibrium reaction shift?

The reaction will not shift to neither direction- there will be no effect.

What will happen if we add an inert gas to the mixture?

There will be no change

When a reaction has equal moles of gas on both sides, what does that mean if we try to alter the volume?

The reaction will shift to the left (think about the heat being a product in an exothermic reaction)

If we raised the temperature in an exothermic reaction, what does that mean for where the reaction shifts?

The temperature will cause the reaction to shift to the right to absorb heat.

If we lowered the temperature in an exothermic reaction, what does that mean for where the reaction shifts?

The reaction will shift to the right (think about the heat being a reactant in an endothermic reaction)

If we raised the temperature in an endothermic reaction, what does that mean for where the reaction shifts?

The reaction will shift to the left

If we lowered the temperature in an endothermic reaction, what does that mean for where the reaction shifts?

It favors products more

When Q < K, what does that mean for the reaction?

It favors reactants more

When Q > K, what does that mean?

Bronsted Acids

These types of acids are H⁺ Donors

Bronsted Bases

These types of bases are H⁺ acceptors

Arrhenius acids

These types of acids form H⁺

Arrhenius Bases

These types of bases form OH^-

Lewis acids

These types of bases accept electron pairs

Lewis bases

These types of bases donate electron pairs

Weak acids

Those binary acids with a strong bond strength are classified as what…?

Electronegativity and # of Oxygen atoms

In oxyacids, what are a few ways to decide whether its a strong or weak acid?

Yes

When we have a strong acid (or strong base), does the reaction completely ionize?

Conjugate acid

This is the acid that is formed from the original base.

Conjugate base

This is the base that is formed from the original acid.

Its neutral

When we have a cation or anion from a strong acid or base, is the cation or anion either an acid or base?

It can be either depending on the situation, but its extremely weak

When we have a cation or anion from a weak acid or base, is the cation or anion either an acid or base?

Yes

For strong acids, can we find the pH directly or no?

We can’t- we will have to do an ICE table to solve for what we want to know.

For weak acids, can we find the pH directly or no?

Yes

Do strong acids normally have a large K_a?