Chem Exam 4

An acid that gives up H+ easily and is essentially 100% dissociated (splits to produce H+ and an anion) in water.

Strong Acid

A base that has a high affinity for H+ and holds it tightly.

Strong Base

Which of the following statements are true regarding an endothermic reaction?

The bonds formed in the products are weaker than the bonds broken in the reactants. Heat is absorbed

An equilibrium reaction is found to shift to the right upon decreasing the temperature of the reaction. What is true about the reaction?

The forward reaction is exothermic The reverse reaction is endothermic

Select all of the statements about energy that are correct.

The lower the potential energy of a compound, the more stable it is. Energy is the capacity to do work Energy can neither be created nor destroyed

What statements describe a reaction at equilibrium?

The net reactant and product concentrations do not change. The rate of the forward reaction equals the rate of the reverse reaction.

CH4 (g) + 2O2 (g) -> CO2(g) + 2H2O (l) H (delta) = -213 kcal/mol Which one has the stronger bonds: reactants or products

The products

A 5-kg mass sitting at a height of 1 meter has a potential energy of 49 joules. Taking into consideration the law of conservation of energy, the maxium kinetic energy it can achieve if it were to fall will be ___.

The same as the original potential energy because the total energy in the universe does not change. Energy cannot be created or destroyed.

What is thermodynamics?

The study of energy, work and heat.

The equilibrium shifts right

The temperature is decreased

The equilibrium shifts left

The temperature is increased

Which is true with regard to reactant and product concentration when a chemical reaction reaches equilibrium?

There is no net change in reactant or product concentration

Acids with three protons to donate, such as phosphoric acid

Triprotic acid

As a rule of thumb, a 10 degrees C rise in temperature causes a reaction rate to double. (T/F)

True

Decrease in temperature will cause an equilibrium to shift in favor of the exothermic reaction so that additional heat is released. (T/F)

True

In all Chemical Reactions, matter will either absorb or release energy. (T/F)

True

Increase in temperature will cause an equilibrium to shift in favor of the endothermic reaction so that additional heat is absorbed. (T/F)

True

The stronger the acid, the weaker its conjugate base; the weaker the acid, the stronger its conjugate base. (T/F)

True

Usually a mixture of a weak acid and its conjugate base is used to prepare a buffer solution. (T/F)

True

Water is a weak acid and like all weak acids, it is slightly dissociated into H+ and OH ions (T/F)

True

We can not measure an absolute value for the energy stored in a chemical system. We can only measure the CHANGE in ENERGY (T/F)

True

An acid that gives up H+ with difficulty and is less than 100% dissociated in water.

Weak Acid

A base that has only a slight affinity for H+ and holds it weakly.

Weak Base

When strong acid is added to a buffer solution, it reacts with the weak ___ that is present, converting it into the weak ____

base, acid

Unit of specific heat is

cal/g oC

A strong acid is an acid that completely _____ in aqueous solutions

dissociates

The process of splitting a Bronsted-Lowry acid into individual ions is known as____

dissociation

One calorie is the amount of heat necessary to raise the temperature?

1 g of water by 1 degrees C

1000 cal = 1000 J = 1 cal = 1 kcal =

1 kcal 1 kJ 4.184 J 4.184 kJ

Favors the products

3.2 * 10^6

Neither side is greatly favored

68

Favors the reactants

8.1*10^-3

Arrhenius base

A compound that produces OH- ions in aqueous solution

For a chemical reaction to occur:

- Reactant particle must collide. • Some chemical bonds have to break. Some chemical bonds have to form. • Not all collisions lead to product; only the colliding molecules approaching with right orientation will form bond

Rank the energies from highest to lowest

0.572 kcal 0.125 kJ 19.9 cal 64.8 J

The behavior of gases can be explained by a group of assumptions known as the kinetic-molecular theory of gases. The assumptions are as follows:

A gas consists of many particles, either atoms or molecules, moving about at random with no attractive forces between them. Because of this random motion, different gases mix together quickly. The amount of space occupied by the gas particles themselves is much smaller than the amount of space between particles. Most of the volume taken up by a gas is empty space, accounting for the ease of compression and low densities of gases. The average kinetic energy of gas particles is proportional to the Kelvin temperature. Thus, gas particles have more kinetic energy and move faster. Collisions of gas particles, either with other particles or with the wall of their container, are elastic; that is, the total kinetic energy of the particles is constant. The pressure of a gas against the walls of its container is the result of collisions of gas particles with the walls.

Bronsted-Lowry base

An H+ acceptor

Which of the following is the correct Arrhenius definition of an acid?

An acid is a substance that produces H+ ions in water

Which of the following are examples of dissociation?

An acid reacts with water to form its conjugate base plus a hydronium ion. An ionic compound is dissolved in water

The volume of a gas is directly proportional to its molar amount at a constant pressure and temperature

Avogadro's Law

The volume of a fixed amount of gas at a constant temperature is inversely proportional to its pressure.

Boyle's Law

A combination of substances that act together to prevent a drastic change in pH.

Buffer

Energy can be measured in which units?

Calories and joules

The volume of a fixed amount of gas at a constant pressure is directly proportional to its Kelvin temperature.

Charles's Law

The substance formed by addition of H+ to a base.

Conjugate Acid

The substance formed by loss of H+ from an acid.

Conjugate Base

• Molecules and atoms in a reaction mixture are in________. • Thus they frequently ______ with each other. • Only some collisions will have enough energy to ______. • When reactant bonds are broken, new bonds MAY be formed and ____

Constant motion collide break bonds products can result

Bond dissociation energy is defined as the heat of reaction, delta H, for breaking a ____ bond by equally dividing the ____ between the two atoms in the bond.

Covalent, electrons

The total pressure exerted by a gas mixture of (Ptotal) is the sum of the partial pressures of the components in the mixture.

Dalton's Law

Order the steps in calculating the concentration of a strong acid by titration with a base of known molarity

Determine the number of moles of based used to neutralized the acid sample Use the balanced equation to determine the number of moles that react with each mole of base Divide the calculated moles of acid by the volume of the acid solution

Acids with two protons to donate, such as sulfuric acid

Diprotic acid

A process or reaction that absorbs heat.

Endothermic

Law of conservation of energy

Energy can neither be created nor destroyed THOUGH it CAN be transformed from one form to another.

Decreased pressure on the system

Equilibrium shifts to the left

Increased pressure on the system

Equilibrium shifts to the right

A process or reaction that releases heat.

Exothermic

The pressure of a gas is directly proportional to its Kelvin temperature for a fixed amount of gas at a constant volume; P α T (in kelvin) or P/T = k (A constant value).

Guy-Lussac's Law

exothermic

H is negative

endothermic

H is positive

Which of the following are common strong Bronsted-Lowry acids?

HNO3 HCl H2SO4

The difference between the energy absorbed in breaking bonds and that released in forming bonds.

Heat of reaction

_____ the activation energy, the lower the number of productive collisions , and slower the reaction. The _____ the activation energy, the greater the number of productive collisions in a given amount of time, and faster the reaction.

Higher Lower

The relationship that combines the four variables P, V, T, and n for gases can be combined into a single expression called the ideal gas law;

Ideal Gas Law

Select all of the statements that correctly describe an amphoteric molecule or ion

It can act as either a base or an acid It contains at least one hydrogen atoms It contains at least one lone pair of electrons

What is a chemical reaction?

John Dalton defined it as something involving the joining, separating, or rearranging of atoms.

SI unit of energy is _______ and the metric unit of energy is ______.

Joules, Calories

Which of the following is the correct acid dissociation constant expression for NH4+

Ka= [H3O+] [NH3]/ [NH4+]

When a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress.

Le Chatelier's Principle

Acids with one proton to donate, such as, hydrochloric acid, HCl; nitric acid, HNO3

Monoprotic acid

A reaction that can go in either direction, from products to reactants or reactants to products.

Reversible Reactions

The amount of heat needed to raise the temperature of 1 g of any substance by 1 degrees C is called the ______ of the substance.

Specific heat

According to the Bronsted-Lowry definition, acids are proton donors. The "proton" being donated is in fact a ____ atom that has lost its electron. Thus, it is an ion that has the symbol _____, and not a proton from the nucleus of an atom.

hydrogen, H+

Adding product will drive the equilibrium to the _____

left

The reaction of a Bronsted-Lowry acid with a hydroxide base is called a ____ reaction. The products of the reaction are ____ and a _____

neutralization water salt

A monoprotic acid contains ____acidic proton

one [HCl]

A Bronsted-Lowry acid-base reaction involves the transfer of a ____ from the ____ to the ____

proton acid base

Adding reactant will drive the equilibrium to the ____

right

Ions that appear on both sides of a balanced equation but do not participate in the reaction are called _____ ions.

spectator

If a chemical system at equilibrium is _____, the system will react in the direction that relieves the _____.

stressed , stress

A triprotic acid contains ___ acidic protons

three [H3PO4]

A diprotic acid contains ___ acidic protons

two [ H2SO4]

Weak acids differ in their relative strength; the same is true of weak bases. If base X is stronger than base Y, then the conjugate acid HX will be ____ than the conjugate acid HY.

weaker

The amount of energy the colliding particles must have for productive collisions to occur. The size of the activation energy determines the reaction rate, or how fast the reaction occurs.

•Activation energy (Ea)

In CHEMICAL REACTIONS:

•Energy cannot be created or destroyed •Energy can be converted from one form to another •Energy conversion occurs with less than 100% efficiency •ALL reactions involve a gain or loss of Energy