Chemistry, Unit 7
22) The standard molar enthalpy of _________ is the amount of energy that is transferred when one mole of a compound is formed from its component elements in their standard states.
formation
Q1) The amount of energy that is transferred when one mole of a compound is formed from its component elements in their standard states is the standard molar enthalpy of ______.
formation
5) Thermochemistry can help a chemist do the following: a. tell how much _______ is transferred in chemical reactions and physical changes. b. predict whether certain substances will _______ with each other. c. predict the _______ of reactions. d. predict what kinds of _______ will occur.
heat react rates reactions
Q1) What kind of enthalpy does a bomb calorimeter measure?
combustion
6 ______ law states that the overall enthalpy change in a reaction is the same whether it occurs in one step or a series of steps.
Hess's
Q1) Which law states that the overall enthalpy change in a reaction is the same whether it occurs in one step or a series of steps?
Hess's
Q1) What is the measurement of enthalpy changes caused by chemical reactions, changes of state, or the formation of a solution?
calorimetry
15) Changes in enthalpy demonstrate the law of _________ because each loss of energy in one place results in an equal gain of energy in another place.
conservation of energy
Q1) Solve this problem. (You will need Table B-12 and Table B-13 in your CRG.) You are conducting a calorimetry experiment using a calorimeter with 500 mL of water in its outer chamber to determine the enthalpy of reaction of a chemical reaction. The initial temperature of the water was 25 °C. After the reaction, the temperature of the water was 57.4 °C. Disregarding any heat loss to the walls of the container, calculate the Hf). (The specific heat of the water is 4.18 J/ (g∙K)
67.7 kJ
3) Physical processes that chemical thermodynamics study are ______ and changes of ______.
??? ; state
13) To the chemist, the law of _______ is interpreted as the amount of energy lost by a chemical reaction is equal to the amount of energy gained.
conservation of energy
reaction kinetics
the field of chemistry that deals with reaction mechanisms and reaction rates
Q1) Solve this problem. (You will need Table B-12 and Table B-13 in your CRG.) Find the ∆Hr⁰ for the reaction of two moles of aqueous ammonium hydroxide and one mole of aqueous calcium chloride that produces two moles of aqueous ammonium chloride and one mole of solid calcium hydroxide. (Hint: Be careful looking up the ∆Hf⁰ for ammonium chloride and calcium hydroxide). 2NH₄OH(aq) + CaCl₂(aq) → 2NH₄Cl(aq) + Ca(OH)₂ (s)
-67.2 kJ
Q1) Solve this problem. (You will need Table B-12 and Table B-13 in your CRG.) Find the ΔHr0 for the reaction of three moles of potassium hydroxide and one mole of phosphoric acid that produces one mole of potassium phosphate and three moles of water. 3KOH(aq) + H₃PO₄(aq) → K₃PO₄(aq) + 3H₂O(l)
-81.4 kJ
2) Complete the table with the data from the lab. NaOH and H₂O
0 seconds: 21°C 10 seconds: 23°C 20 Seconds: 27°C 30 seconds: 32°C 40 seconds: 34°C
1) Complete the table with the data from the lab. Na₂S₂O₃ and H₂O
0 seconds: 21°C 20 seconds: 19°C 40 seconds: 17.5°C 60 seconds: 16°C 80 seconds: 15°C
7) Place in order(1-4) the steps followed to produce carbon monoxide by the combustion of carbon graphite in a limited oxygen environment.
1. carbon and oxygen combine to form CO2 2. carbon and oxygen combine to form CO2 3. carbon and oxygen combine to form CO2 4. the liberated oxygen combines with carbon to form more CO2 that breaks down into CO and O2 again, and the cycle continues
25) One mole of hydrogen gas (H2), reacts with one mole of bromine Br2(g) to produce 2 moles of hydrogen bromide gas (HBr). The reaction releases 72.58 kJ of heat. Which equation is the correct form to show the standard molar enthalpy of formation?
1/2 H₂(g) + 1/2 Br₂(l) → Hbr(g)∆Hf⁰ = -36.29 kJ
13) Calculate the ΔGr0 of the following reaction and state whether it is spontaneous at standard temperature or not. (You will need table B-12 in your CRG) CaCO3(s) → CaO(s) + CO2(g)
131.38 kJ, no
27) Which statement is true about the thermochemical equation below: 2H₂(g) + O₂ → 2H₂O(g) + 285.83 kJ
The reaction is exothermic and releases 285.83 kJ of heat.
3) What is an endothermic reaction?
An endothermic reaction is when heat is absorbed during a reaction.
26) The standard molar enthalpy of ________ is the amount of heat transferred during the complete combustion of one mole of a reactant in its standard state.
combustion
5) A bomb calorimeter is used to measure the enthalpy of ______.
combustion
11) Also called the law of _____ of energy, the first law of thermodynamics states that the total amount of energy in a thermodynamic system remains constant.
conservation
10) _______, which is a measure of the energy that is unavailable to perform work, is also the measure of randomness, or disorder, of a thermodynamic system.
Entropy
7) A thermodynamic function called __________ free energy measures the capacity of a system to perform work.
Gibbs
8) The difference between the change in enthalpy and the product of the change in entropy and the Kelvin temperature in a system at a constant temperature and pressure is called standard _________ free energy of reaction.
Gibbs
9) The Gibbs free energy of one mole of a substance in its standard state is the standard molar ______ free energy of formation.
Gibbs
18) How does a cube of ice melting in a glass of water in a warm room demonstrate the law of entropy?
Heat flows from the water to melt the ice and increases the entropy of the system.
8) Hess's law can be applied in the following rules:
If a reaction contains intermediate steps, the overall enthalpy change of the reaction is equal to the sum of the enthalpy changes of the intermediate steps. To find the enthalpy of formation of a compound, you can use the enthalpy changes of reactions that involve the elements that make up the compound, even if those reactions are not necessarily intermediate steps in the production of that compound. Known enthalpy changes can be combined to calculate unknown enthalpies of reaction. Thermochemical equations may be reversed, if necessary, to calculate unknown enthalpies, as long as the sign of the enthalpy value also changes.
4) What is an exothermic reaction?
If the energy required to create the bonds between the solute and solvent is less than the energy needed to break the solute/solute bonds and the solvent/solvent bonds, the reaction is exothermic, meaning that energy was released.
20) How does the law of entropy apply to chemical reactions?
If there is a difference in the amount of energy between the reactants and the products, the reaction will proceed in the direction that produces the highest entropy.
5) What is true about spontaneous reactions?
Some reactions are spontaneous only if energy from outside the system is constantly added. Some reactions are spontaneous, but they proceed very slowly over long periods of time. Some spontaneous reactions occur quickly, as soon as the reactants are mixed, without the application of additional energy. Some reactions are spontaneous only at high temperatures.
6) What is Not true about spontaneous reactions?
Spontaneous reactions are always endothermic. The reverse reactions will also be spontaneous. Spontaneous reactions are always reactant favored.
4) How does a calorimeter measure the enthalpy change of a chemical reaction?
The heat of the reaction raises the temperature of the water. By multiplying the specific heat of the water by the mass of the water and the change in temperature of the water, you can calculate the amount of heat released or absorbed by the reaction. The heat of the reaction is transferred through the walls of the reaction chamber to the water in the outer chambers.
21) Which of the following statements would be true about a system in which the total enthalpy of the reactants is greater than the enthalpy of the products?
The ΔHr⁰ would be negative and the reaction would be exothermic.
Q1) Which of the following apply to Hess's law? Select all that apply.
Thermochemical equations may be reversed, if necessary, to calculate unknown enthalpies, as long as the sign of the enthalpy value also changes. Known enthalpy changes can be combined to calculate unknown enthalpies of reaction. If a reaction contains intermediate steps, the overall enthalpy change of the reaction is equal to the sum of the enthalpy changes of the intermediate steps. To find the enthalpy of formation of a compound, you can use the enthalpy changes of reactions that involve the elements that make up the compound, even if those reactions are not necessarily intermediate steps in the production of that compound.
Q1) ______ is the branch of chemistry that studies the heat transfers that accompany chemical or physical changes.
Thermochemistry
thermochemical equation
a balanced chemical equation that includes the amount of heat energy involved in a reaction
spontaneous reaction
a chemical reaction in which the reactants are converted into products without the constant addition of energy from outside the thermodynamic system to sustain the reaction
entropy
a measure of the energy that is unavailable (not available) to perform work; the measure of randomness, or disorder, of a thermodynamic system
thermodynamic system
a precisely defined portion of the universe that is being studied according to the amount of energy that is being transferred; the reactants, products, and chemical processes that accompany a chemical reaction
Hess's law
a principle of chemical thermodynamics that states that the overall enthalpy change in a reaction is the same whether it occurs in one step or in a series of steps
law of entropy
a scientific law that states that for any thermodynamic system not in thermodynamic equilibrium, energy will move to increase entropy; the second law of thermodynamics
law of conservation of energy
a scientific law that states that the total amount of energy in a thermodynamic system remains constant—it is neither created nor destroyed; the first law of thermodynamics
Gibbs free energy
a thermodynamic function that measures the capacity of a system to perform work
activated complex
a transitional substance that results when reactant bonds are broken, and persists while product bonds are being formed
16) The entropy of a substance will never be zero because:
a value of S = 0 could only occur if molecular motion completely stopped at a temperature of absolute zero
7) The first law of thermodynamics, also called the law of ________ of energy, states that the total amount of energy in a thermodynamic system remains constant.
conservation
calorimeter
an apparatus used to measure changes in enthalpy
2) An apparatus used to measure changes in enthalpy is a __________.
calorimeter
3) The measurement of enthalpy changes caused by chemical reactions, changes of state, or the formation of a solution is called _______.
calorimetry
Q1) Some physical processes that chemical thermodynamics studies are: Select all that apply.
dissolution ; changes of state
9) The total amount of energy in a thermodynamic system is called ________.
enthalpy
Q1) The total amount of energy in a thermodynamic system is called ___________.
enthalpy
17) Another way to describe __________ is the measure of disorder in a system.
entropy
8) The second law of thermodynamics, also called the law of ________, states that for any thermodynamic system not in thermodynamic equilibrium, energy will move to increase entropy.
entropy
Q1) Also called the law of ______ is the second law of thermodynamics, which states that for any thermodynamic system not in thermodynamic equilibrium, energy will move to increase entropy.
entropy
5) Which reaction was the heat of the solution positive? Which reaction was the heat of the solution negative?
first reaction second reaction
Q1) A chemist can use thermochemistry to do the following: a. tell how much ______ is transferred in chemical reactions and physical changes. b. predict whether certain substances will ______ with each other. c. predict the ______ of reactions. d. predict what kinds of ______ will occur.
heat react rates reactions
3) The overall sequence of steps that makes up a chemical reaction is called the reaction __________.
mechanism
10) The ΔGr0 of a reaction that is product-favored and spontaneous will be _____.
negative
12) The ΔGr0 of a reaction that is reactant-favored and not spontaneous will be _____.
positive
23) The standard molar enthalpy of formation of an unstable compound is _____.
positive
1) The field of chemistry that deals with reaction mechanisms and reaction rates is _________ kinetics.
reaction
19) The amount of heat transferred when the number of moles of reactants specified in a chemical equation is completely converted into products in their standard states is called the standard molar enthalpy of ________________.
reaction
Q1) The standard molar enthalpy of _____ is the amount of heat transferred when the number of moles of reactants specified in a chemical equation is completely converted into products in their standard states.
reaction
2) The tendency of a reaction to occur without the application of outside force or energy to sustain the reaction is reaction ___________.
spontaneity
4) A(n) ___________ reaction is a chemical reaction in which the reactants are converted into products without the constant addition of energy from outside the thermodynamic system to sustain the reaction.
spontaneous
12) The _______ state of a substance is the state (solid, liquid, or gas) of that substance at room temperature (25°C or 298 K) and a pressure of 100 kPa.
standard
1) The result of the addition of one or more terms ______.
summation
4) Chemical processes that involve chemical thermochemistry are: a. _________ reactions: two or more substances combine to form a new compound b. _________ reactions: a single compound undergoes a chemical reaction to produce two or more component substances c. _________ reactions: a substance ionizes and recombines to become another substance d. _________ reactions: a substance burns in oxygen
synthesis decomposition single-displacement & ??? combustion
standard molar Gibbs free energy of formation
the Gibbs free energy of one mole of a substance in its standard state
standard molar enthalpy of formation
the amount of energy that is transferred when one mole of a compound is formed from its component elements in their standard states
standard molar enthalpy of combustion
the amount of heat transferred during the complete combustion of one mole of a reactant in its standard state
standard molar enthalpy of reaction
the amount of heat transferred when the number of moles of reactants specified in a chemical equation is completely converted into products in their standard states
thermochemistry
the branch of chemistry that studies the heat transfers that accompany chemical and physical changes
standard Gibbs free energy of reaction
the difference between the change in enthalpy and the product of the change in entropy and the Kelvin temperature in a system at a constant temperature and pressure
calorimetry
the measurement of enthalpy changes caused by chemical reactions, changes of state, or the formation of a solution
activation energy
the minimum energy required to start a chemical reaction
reaction mechanism
the overall sequence of steps that makes up a chemical reaction
summation
the result of the addition of one or more terms
standard state
the state of a substance (solid, liquid, or gas) at room temperature (25 °C or 298 K) and a pressure of 100 kPa
chemical thermodynamics
the study of the relationship between heat and work within chemical reactions or physical changes of state
reaction spontaneity
the tendency of a reaction to occur without the application of outside force or energy to sustain the reaction
enthalpy
the total amount of energy in a thermodynamic system
6) A(n) ______________ equation is a balanced chemical equation that includes the amount of heat energy involved in a chemical reaction
thermochemical
2) The branch of chemistry that studies the heat transfers that accompany chemical or physical changes is _________.
thermochemistry
11) A precisely defined portion of the universe that is being studied according to the amount of energy that is being transferred is a(n) _______ system, which also refers to the reactants, products, and chemical processes that accompany a chemical reaction.
thermodynamic
14) In thermochemistry, a ___________ refers to the reactants, products, and chemical processes that accompany a chemical reaction.
thermodynamic system
1) The study of the relationship between heat and work within chemical reactions or physical changes of state is called chemical ________________.
thermodynamics
12) Chemical _____ is the study of the relationship between heat and work within chemical reactions or physical changes of state.
thermodynamics
vvv Lab: Heat of a Solution vvv
vvv Lab: Heat of a Solution vvv
vvv Lesson 3 vvv
vvv Lesson 3 vvv
vvv Quiz 1 vvv
vvv Quiz 1 vvv
11) If the ΔGr0 of a reaction is __________, the reaction is at equilibrium and does not favor product or reactant.
zero
24) The enthalpy of formation of an uncombined element is __________.
zero
10) Solve the problem: (You will need Table B-12 in your CRG) Find the ΔHr0 for the reaction of one mole of solid magnesium carbonate that decomposes into one mole of solid magnesium oxide and one mole of carbon dioxide gas. MgCO3(s)→MgO(s) + CO2(g)
∆Hr⁰ = +117.0kJ
11) Solve the problem: (You will need Table B-12 in your CRG) Find the ΔHr0 for the reaction of two moles of potassium iodide and one mole of lead (II) nitrate to form 2 moles of potassium nitrate and one mole of lead (II) iodide. 2KI(aq) + Pb(NO3)2(aq)→2KNO3(aq) + PbI2(s)
∆Hr⁰ = -53.1kJ
9) Solve the problem: (You will need Table B-12 in your CRG) You are conducting a calorimetry experiment using a calorimeter with 500mL of water in its outer chamber to determine the enthalpy of reaction of a chemical reaction. The initial temperature of the water is 25°C. After the reaction, the temperature of the water is 32.5°C. Disregarding any heat loss to the walls of the
∆Hr⁰ = 15.7 kJ
