Unit 9 Chemistry Review

Decide whether the temperature of a liquid-vapor equilibrium system should be increased or decreased to make each of the following changes in the system. An increased final concentration of vapor a. Increased b. Decreased

a. Increased

Which of the following will increase the frequency of successful collisions? a. Increasing the temperature b. Decreasing the pressure c. Decreasing the concentration

a. Increasing the temperature

Given the reaction below at equilibrium W(g) + 3X(g) <-> 2Y(g) + 3Z(g) An increase in pressure at constant temperature will shift equilibrium to the a. Left, and the concentration of W(g) will increase b. Left, and the concentration of W(g) will decrease c. Right, and the concentration of W(g) will increase d. Right, and the concentration of W(g) will decrease

a. Left, and the concentration of W(g) will increase

The reaction below is at equilibrium: C(s) + O2(g) <-> CO2(g) If the concentration of C(s) is increased, the equilibrium point will shift a. Right, and the concentration of O2(g) will increase b. Right, and the concentration of O2(g) will decrease c. Left, and the concentration of O2(g) will increase d. Left, and the concentration of O2(g) will decrease

a. Right, and the concentration of O2(g) will increase

Given the reaction at equilibrium: SO2(g) + NO2(g) <-> SO3(g) + NO(g) As NO(g) is removed from the system, the concentration of a. SO3(g) will increase b. NO2(g) will increase c. SO2(g) will increase d. SO2(g) and NO2(g) will both be equal

a. SO3(g) will increase

Given the equilibrium reaction SO2(g) + NO2(g) <-> SO2(g) + NO(g) + heat Which stress will NOT shift the equilibrium point of this reaction? a. decreasing pressure b. decreasing SO2(g) concentration c. increasing heat d. increasing NO(g) concentration

a. decreasing pressure

Predict the effect of each of the following on the indicated equilibrium system in terms of which reaction will be favored(forward, reverse, or neither). H2(g) + Cl2(g) ⇄ 2HCl(g) + 184 kJ addition of Cl2 a. forward b. reverse c. neither

a. forward

Predict whether each of the following pressure changes would favor the forward or reverse reaction. 2NO(g) + O2(g) ⇄ 2NO2(g) a. increased pressure b. decreased pressure

a. forward b. reversed

The following liquid-vapor is at equilibrium at a given temperature in a closed system. liquid + heat energy ⇄ vapor Suppose the temperature is increased and equilibrium is established at the higher temperature. How does the final value of each of the following compare with its initial value? a. higher b. lower c. same

a. higher

This system has reached equilibrium: N2(g) + 3H2(g) <-> 2NH3(g) + heat What happens to K if the temperature is decreased? a. increases b. decreases c. increases or decreases d. does not change

a. increases

Which of the following will increase the frequency of successful collisions? a. increasing the temperature b. decreasing the pressure c. decreasing the concentration

a. increasing the temperature

For each of the following pairs, choose the substance or process you would expect to react more rapidly. a. Granulated sugar or powdered sugar b. Zinc in HCl at 298.15K or zinc in HCl at 410K c. 5g of thick platinum wire or 5g of thin platinum wire

a. powdered sugar b. Zinc in HCl at 410K c. 5g of thin platinum wire

What does the curve represent?

all the molecules that have a potential to interact

In chemistry, activation energy is the energy required to...

allow a reaction to happen

A 1 g piece of copper will react the slowest in a. 1 M HNO3(aq) because there will be more effective collisions b. 1 M HNO3(aq) because there will be fewer effective collisions c. 2 M HNO3(aq) because there will be more effective collisions d. 2 M HNO3(aq) because there will be fewer effective collisions

b. 1M HNO3(aq) because there will be fewer effective collisions

At 20⁰C, a 1.2 gram sample of Mg ribbon reacts rapidly with 10.0 milliliters of 1.0 M HCl(aq). Which change in conditions would have caused the reaction to proceed more slowly? a. Increasing the initial temperature to 25⁰C b. Decreasing the concentration of HCl(aq) to 0.1 M c. Using 1.2 g of powdered Mg d. Using 2.4 g of Mg ribbon

b. Decreasing the concentration of HCl(aq) to 0.1 M

Given the equilibrium reaction A + B <-> AB + heat If the concentration of AB is decreased, the rate of forward reaction will a. Increase, and [B] will also increase b. Increase, and [B] will decrease c. Decrease, and [B] will also decrease d. Decrease, and [B] will increase

b. Increase, and [B] will decrease

Which of the following would speed up a reaction? a. Using lumps instead of power b. Increasing the concentration of an acid c. Decreasing the temperature

b. Increasing the concentration of an acid

Given the reaction: H2O(l) + 286 kJ <-> H2(g) + 1/2 O2(g) Which statement describes the forward reaction? a. It is the endothermic and releases 286 kJ b. It is endothermic and absorbs 286 kJ c. It is exothermic & releases 286 kJ d. It is exothermic & absorbs 286 kJ

b. It is endothermic & absorbs 286 kJ

A thermometer is in a beaker of water. Which statement best explains why the thermometer reading initially increases when LiBr(s) is dissolved in the water? a. The dissolving of the LiBr(s) is endothermic, so energy is gained by the water b. The dissolving of the LiBr(s) is exothermic, so energy is gained by the water c. The dissolving of the LiBr(s) is endothermic, so energy is lost by the water d. The dissolving of the LiBr(s) is exothermic, so energy is lost by the water

b. The dissolving of the LiBr(s) is exothermic, so energy is gained by the water

If the pressure on the equilibrium system of N2(g) + 3H2(g) <-> 2NH3(g) is increased a. The quantity of N2(g) increases b. The quantity of NH3(g) increases c. The quantity of H2(g) decreases d. The quantities in the system do not change

b. The quantity of NH3(g) increases

What happens to the concentration of vapor when a liquid-vapor system at equilibrium experiences an decrease in temperature? liquid + heat energy ⇄ vapor a. increase b. decrease

b. decrease

Given the reaction a equilibrium: 2HBr(g) + 73 kJ <-> H2(g) + Br2(g) As the temperature decreases, the concentration of H2(g) a. increases b. decreases c. remains the same

b. decreases

Predict the effect of each of the following on the indicated equilibrium system in terms of which reaction will be favored(forward, reverse, or neither). H2(g) + Cl2(g) ⇄ 2HCl(g) + 184kJ increased temperature a. forward b. reverse c. neither

b. reverse

Given the reaction: H2 + Br2 --> 2HBr + 73 KJ The heat of reaction, /\H, is a. +73, because energy is released b. +73, because energy is absorbed c. -73, because energy is released d. -73, because energy is absorbed

c. -73, because energy is released

Given the reaction: A --> B + energy Which statement is true of the reaction below? a. A has more energy than B, and /\H is positive b. B has more energy than A, and /\H is positive c. A has more energy than B, and /\H is negative d. B has more energy than A, and /\H is negative

c. A has more energy than B, and /\H is negative

Given the reaction: 2SO4(g) + O2(g) <-> 2SO3(g) If the pressure is increased on the reaction, there will be a. A decrease in concentration of SO3 b. An increase in concentration of SO2 c. A shift of equilibrium to right d. A shift in equilibrium to left

c. A shift of equilibrium to right

Of the following, ____ will lower the activation energy for a reaction. a. increasing the concentrations of reactants b. raising the temperature of the reaction c. adding a catalyst for the reaction d. removing products as the reaction proceeds

c. adding a catalyst for the reaction

Which changes can reach equilibrium? a. chemical changes, only b. physical changes, only c. both physical & chemical changes d. neither physical nor chemical changes

c. both physical & chemical changes

Given the equilibrium reaction H2 + Cl2 + energy <-> 2HCl Which change will cause the concentration of H2 to decrease? a. decreasing Cl2 b. decreasing pressure c. increasing temperature d. increasing HCl

c. increasing temperature

Predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium. H2(g) + Cl2(g) ⇄ 2HCl(g) Which way will this shift? a. left b. right c. no shift

c. no shift

Given the reaction at equilibrium 2HCl(g) <-> H2(g) + Cl2(g) As pressure is decreased at constant temperature, the concentration of HCl a. decreases b. increase c. remains the same

c. remains the same

Equilibrium is best described as _____.

continuing to find balance as the circumstances change

A2(g) + B2(g) --> 2AB(g) + heat An increase in concentration of A2(g) increases the rate of the reaction because of a. A decrease in activation energy b. An increase in activation energy c. A decrease in frequency of collision d. An increase in frequency of collision

d. An increase in frequency of collision

Given the reaction: A2(g) + B2(g) -->> 2AB(g) + heat An increase in concentration of A2(g) increases the rate of the reaction because of a. A decrease in activation energy b. An increase in activation energy c. A decrease in frequency of collision d. An increase in frequency of collision

d. An increase in frequency of collision

Given the reaction a equilibrium: N2(g) + 3H2(g) <-> 2NH3(g Increasing the concentration of NH3(g) will cause a. A decrease in the concentration of N2(g) b. A decrease in the concentration of H2(g) c. An increase in the rate of forward reaction d. An increase in the rate of reverse reaction

d. An increase in the rate of reverse reaction

Which conditions will increase the rate of a chemical reaction? a. Decreased temperature and decreased concentration b. Decreased temperature and increased concentration c. Increased temperature and decreased concentration d. Increased temperature and increased concentration

d. Increased temperature and increased concentration

Given the system at equilibrium: 2NO2(g) <-> N2O4(g) + 58.1 kJ When the temperature is increased at constant pressure, concentration of a. N2O4 will increase, because the forward rate increases b. N2O4 will increase, because the reverse rate increases c. NO2 will increase, because the forward rate increases d. NO2 will increase, because the reverse rate increases

d. NO2 will increase, because the reverse rate increases

Given the reaction XW + energy --> W Which is true of this reaction? a. The reaction is exothermic with -/\H b. The reaction is exothermic with +/\H c. The reaction is endothermic with -/\H d. The reaction is endothermic with +/\H

d. The reaction is endothermic with +/\H

Given the equilibrium reaction 2A(g) + B(g) <-> C(g) + 42 kJ If more heat is added to the reaction, a. [A] and [C] will both decrease b. [A] and [C] will both increase c. [A] will decrease, but [C] will increase d. [A] will increase, but [C] will decrease

d. [A] will increase, but [C] will decrease

Which description applies to a system in a sealed flask that is half full of water? a. only evaporation occurs, but it eventually stops b. only condensation occurs, but it eventually stops c. neither evaporation nor condensation occurs d. both evaporation and condensation occur

d. both evaporation and condensation occur

A catalyst increases the rate of a reaction by a. increasing the concentration of reactant(s) b. decreasing the concentration of the reactant(s) c. increasing the activation energy of the overall reaction d. decreasing the activation energy of the overall reaction

d. decreasing the activation energy of the overall reaction

A catalyst increases the rate of reaction by a. increasing the concentration of reactant(s). b. decreasing the concentration of the reactant(s) c. increasing the activation energy of the overall reaction. d. decreasing the activation energy of the overall reaction.

d. decreasing the activation energy of the overall reaction

Given the reaction at equilibrium: 4Hcl(g) + O2(g) <-> 2Cl2(g) + 2H2O(g) If the volume on the system is decreased, the concentration of Cl2(g) will a. decrease, because the reverse rate will decrease b. decrease, because the reverse rate will increase c. increase, because the forward rate will decrease d. increase, because the forward rate will increase

d. increase, because the forward rate will increase

Which conditions will increase the rate of a chemical reaction? a. decreased temperature & decreased concentration b. decreased temperature & increased concentration c. increased temperature & decreased concentration d. increased temperature & increased concentration

d. increased temperature & increased concentration

Which of the following would NOT increase the rate of reaction? a. raising the temperature b. adding catalyst c. increasing the concentration of the reactants d. increasing the volume of the container

d. increasing the volume of the container

Which of the following would NOT increase the rate of reaction? a. raising the temperature b. adding catalyst c. increasing the concentration of the reactants d. increasing the volume of the container

d. increasing the volume of the container

Which of the following would NOT increase the rate of reaction? a. raising the temperature b. adding catalyst c. increasing the concentration of the reactants d. increasing the volume of the container

d. increasing the volume of the container

Which explains what happens to the liquid vapor system when the temperature is reduced? liquid + heat energy ⇄ vapor a. the concentration of vapor & liquid increases b. the concentration of vapor increases & liquid decreases c. the concentration of vapor & liquid decreases d. the concentration of vapor decreases & liquid increases

d. the concentration of vapor decreases & liquid increases

Higher temperatures tend to feed _____ reactions.

endothermic

What are 2 things that are required for reactions to occur?

enough energy and the proper orientation

Collision theory states that you need...

enough energy for the reaction to occur

What is another word for balance?

equilibrium

True or False: Reactions stop once they reach equilibrium.

false

What is the sign on delta H for an exothermic reaction?

negative

What is the sign on delta H for an endothermic reaction?

positive

What does "n" represent in the mathematical formula for Hess's Law?

# of moles

Lithium reacts with oxygen much faster than iron. Which of the following explains this? 1. Nature of the reactants 2. Concentration of the Reactants 3. Temperature of the Reactants 4. Use of a catalyst 5. Surface Area

1. Nature of the reactants

A mixture of gases react faster when the volume they occupy decreased? Which rate influencing factor explains this? 1. Nature of the Reactants 2. Concentration of the Reactants 3. Temperature of the Reactants 4. Use of a catalyst 5. Surface Area

2. Concentration of the reactants

A mixture of gases react faster when volume they occupy is decreased. Which rate influencing factor explains this? 1. nature of the reactants 2. concentration of the reactants 3. temperature of the reactants 4. use of a catalyst 5. surface area

2. concentration of the reactants

Sliced meat left on the counter begins to feel slimy and smell spoiled sooner than the sliced meat in the refrigerator. Which rate influencing factor explains this? 1. Nature of the reactants 2. Concentration of the reactants 3. Temperature of the reactants 4. Use of a catalyst 5. Surface area

3. Temperature of the reactants

Sliced meat begins to feel slimy and smell spoiled. This is due to decomposition reactions with oxygen or carbon dioxide in the air. Which rate influencing factor explains this? 1. Nature of the Reactants 2. Concentration of the Reactants 3. Temperature of the Reactants 4. Use of a catalyst 5. Surface Area

5. Surface Area

Why do chemists use standard states?

Because data collected under standard conditions can be more easily used.

Exothermic reactions fair better at _____ temperatures.

Low

How does an enzyme or catalyst affect the rate of reaction?

Lowers the activation energy

What happens to the reaction when there is an increase in temperature?

More molecules have are able to react

When a reaction is exothermic the enthalpy (delta H) will be_________.

Negative

Predict the effect of each of the following on the individual equilibrium system in terms of which reaction will be forward (forward, reverse, or neither). H2(g) + Cl2(g) ⇄ 2HCl(g) + 184 KJ Decreased Pressure

Neither

Does temperature change the activation energy for a reaction?

No

Predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium. H2(g) + Cl2(g) ⇄ 2HCl(g) Which way will this shift?

No shift

At the end of the curve are the...

Products

At the beginning of the curve are the...

Reactants

When equilibrium is reached, the concentration of reactants ______ and the concentration of products ________.

Remains the same (for both)

Predict the effect of each of the following on the individual equilibium system in terms of which reaction will be forward (forward, reverse, or neither). H2(g) + Cl2(g) ⇄ 2HCl(g) + 184 KJ Removal of H2

Reverse

Reactions are _____ when they can go forward or backward without any extra energy being used.

Reversible

If you increase the concentration of the reactants, which way does the reaction shift?

Right

Predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium. 2H2O2(aq) ⇄ 2H2O(l) + O2(g) Which way will this shift?

Right

Predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium. NH4Cl(s) ⇄ NH3(g) + HCl(g) Which way will this shift?

Right

Is enthalpy a state function, or pathway dependent?

State

What is the defining feature of a "State Function"?

State functions describe the state of a system, and DO NOT depend on the pathway.

In calorimetry, a reaction takes place inside an insulated vessel and the change in ____ is measured.

Temperature

We can determine how much useful energy is contained in nearly any chemical compound by measuring what?

Temperature changes during chemical reactions

What do the molecules on the right side of the Activation energy line have?

The molecules have the proper amount of energy for a chemical reaction to occur.

When you measure delta H (enthalpy) on a graph you measure from the

reactant to product

When a reaction makes more of the "products" side, we say that it is shifting to the _____.

right

What is another name for the transition state between reactants and products called?

Activated Complex

If the temperature of the system is decreased, the concentration of O2 will 2Cl + H2O + energy ⇄ 2HCl

Decrease, and equilibrium will shift to left

When a reaction takes place and enthalpy changes, _____ is transferred into or out of chemical bonds.

Energy

When the amount of forward reactions equals the amount of reverse reactions, we can say that the system has reached _____.

Equilibrium

True or False: All reactions end with pure products.

False

Predict the effect of each of the following on the indicated equilibrium system in terms of which reaction will be favored(forward, reverse, or neither). H2(g) + Cl2(g) ⇄ 2HCl(g) + 184 KJ Decreased temperature

Forward

The change in enthalpy is equal to the heat ______ or ______ by the system.

Gained, Lost

Changes in pressure will affect equilibrium the most for a _____.

Gas

Heat energy and work energy are different because:

Heat energy moves atoms and molecules while work energy moves larger objects.

What happens to the concentration of vapor when a liquid-vapor system at equilibrium experiences an increase in temperature? liquid + heat energy ⇄ vapor a. increase b. decrease

Increase

Decide whether the temperature of a liquid-vapor equilibrium system should be increased or decreased to make each of the following changes in the system. An increased final rate of condensation a. increased b. decreased

Increased

What does the double arrow symbolize?

The reaction can go forward or backward.

True or False: A catalyst changes the activated complex

True

True or false? You must have a balanced chemical equation when using Hess's Law.

True

The chemical reactions we've talked about so far only go one way: the forward reaction. What does this mean?

that the reactants interact to form the products only

The activation energy is the energy that is left on the curve after you measure...

the energy change from reactants to products

What happens in a reverse reaction?

the products change back into the reactants

Le Chatelier's Principle says that a system in equilibrium _____.

will move in the direction that minimizes stress