Chemistry Reading 6c

Given the following thermochemical equations: Equation A: 2C(s) + O2(g) → 2CO(g); ΔH = -221.0 kJ Equation B: C(s) + O2(g) → CO2(g); ΔH = -393.5 kJ Calculate the enthalpy change for the reaction CO(g) + 1/2O2(g) → CO2(g).

-283.0kJ

P4(s) + 3O2(g) → 2P2O3(s); ΔH = -1640.1 kJ P4(s) + 5O2(g) → 2P2O5(s); ΔH = -2940.1 kJ What is the total enthalpy change for the reaction P2O3(s) + O2(g) → P2O5(s)?

-650.0 kJ

Given the following thermochemical equations: 3A → 2B; ΔH = x kJ C → B; ΔH = y kJ What would be the total enthalpy change when the following reactions are summed to yield 3/2A → C?

1/2 x-y

Which of the following reactions is associated with the standard enthalpy of formation of NH3 (g)?

1/2N2(g) + 3/2H2(g) → NH3(g)

Which of the following equations is associated with the standard enthalpy of formation of P2O5(s)?

1/2P4(s) + 5/2O2(g) → P2O5(s)

Which of the following are standard state conditions of temperature and pressure? Select all that apply

298 K 1 atm

Select the two equations below that can be manipulated together to give the equation 3H2(g) + O3(g) → 3H2O(g).

2H2(g) + O2(g) → 2H2O(g) 3O2(g) → 2O3(g)

Consider the following reactions: 2A → B; ΔH = x 2B → C; ΔH = y What is the total enthalpy change for the reaction 4A → C?

2x + y

To generate the overall equation A → 2C, which two equations should be added together?

B → 2C A → B

Which of the following reactions would have an enthalpy change equal to ΔHf degrees? Select all that apply.

C(graphite) + O2(g) → CO2(g) Fe(s) + 3232Cl2(g) → FeCl3(s)

What is the net equation when the following reactions are summed? 2C(graphite) + 3H2(g) → C2H6(g) C2H4(g) → 2C(graphite) + 2H2(g)

C2H4(g) + H2(g) → C2H6(g)

Which of the following statements correctly describe the enthalpy changes associated with the formation of a solution? Select all that apply.

Energy is released when the solvent and solute particles attract each other and mix to form a solution. Energy is absorbed to separate the solvent particles from each other. The overall enthalpy change for the solution process depends on the balance of energy absorbed vs. energy released.

Which of the following substances would have a standard enthalpy of formation equal to 0 kJ/mol? Select all that apply.

H2(g) Hg(l) Ar(g)

For a reaction that proceeds through a series of steps, ΔH overall = ΔH1+ ΔH2+ ΔH3... This is a restatement of ____ law.

Hess's

Generate the equation A + 2B → 2D from a combination of the reactions provided. Reaction 1: A + 2B → 2C Reaction 2: C → D How must reactions 1 and 2 be combined to sum to the overall reaction?

Reaction 1 + 2(Reaction 2)

Match the effects of the following combinations of Reactions 1 and 2 with the reaction resulting from these combinations. Reaction 1: A → 2C Reaction 2: C → B

Rxn 1 + (-Rxn 2) = A + B → 3C Rxn 1 + 2(Rxn 2) = A → 2B (-Rxn 1) + (-Rxn 2) = B + C → A

Which step(s), involved in the formation of a solution, is/are associated with a positive sign for ΔH? Select all that apply.

Solute particles separate from each other. Solvent particles separate from each other.

The standard enthalpy of formation of a compound can be directly determined when ____.

The compound can be readily synthesized from its elements in their standard states

ΔH degrees rxn

The enthalpy change of a reaction measured at the standard state.

ΔH degrees f

The enthalpy change when 1 mole of a compound forms from its elements in their standard states.

Standard enthalpy of formation

The heat change that results when one mole of a compound is formed from its elements in their standard states. Change of HF degrees

Select all the statements that correctly describe the heat of hydration for an ionic compound.

The heat of hydration is the enthalpy change that occurs when an ion is surrounded by water molecules. If ΔHhydr < 0, it indicates that more energy is released due to ion-H2O attraction than the energy absorbed in separating the water molecules.

ΔH degrees for a reaction is calculated using the equation ΣnΔHoffo(products) - ΣmΔHoffo(reactants). Which of the following statements correctly interpret this equation? Select all that apply.

The superscript "o" indicates that the reaction takes place at 1 atm. ΔHoffo for each substance must be multiplied by the appropriate coefficient from the balanced equation. ΔHoffo indicates the standard enthalpy of formation for each substance.

Which of the following options correctly describe the term "standard state" used in thermodynamics? Select all that apply.

To be in its standard state, a substance must be at a pressure of 1 atm. An element in its most stable form at 1 atm is in its standard state.

n and m

coefficients for reactants and products from balanced equation

ΔH degrees for a reaction is calculated using the equation ΣnΔHoffo(products) - ΣmΔHoffo(reactants). In this equation the terms n and m refer to the stoichiometric ____ from a balanced equation, while ΔHoffo represents the standard enthalpies of ____ of the substances in the reaction.

coefficients; formation

ΔH degrees for a reaction is calculated using the equation ΣnΔHoffo(products) - ΣmΔHoffo(reactants). In this equation the terms n and m refer to the stoichiometric _____ from a balanced equation, while ΔHoffo represents the standard enthalpies of ___ of the substances in the reactions.

coefficients; formation

By definition, the standard enthalpy of formation of a pure ___ in its standard state is equal to 0kJ/mol

element

If a particular solution process is exothermic, the subsequent dilution of this solution will be an ____ process.

exothermic

When an ionic compound dissolves in water, the ions dissociate and each individual ion is surrounded by water molecules. The ions are described as being ____.

hydrated

Heat of dilution

is the heat change associated wit the dilution process.

For an ionic substance, the heat of hydration is equal to the enthalpy change for the process of converting 1 ___ of ___ substance to an equal amount of hydrated ions.

mole; gaseous

The standard enthalpy of formation of a compound is the enthalpy change associated with the reaction that generates ____ mole(s) of that compound from its component ____ when all of the substances are under ____ conditions.

one, elements, standard

The lattice energy of an ionic compound is the energy required to convert one mole of the compound from the ___ phase to the ___ phase.

solid; gaseous

ΔH degree f

standard enthalpy of formation

Degree

standard state

Hess's law states that the enthalpy change for an overall process is equal to the ___ of the enthalpy changes for the individual steps.

sum

Σ

sum of

Hess's law states that the enthalpy change for an overall process is equal to ___.

the sum of the enthalpy changes for the individual steps

Hess's Law is

when reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.

A → 2B; ΔH = x kJ B → C; ΔH = y kJ What would be the enthalpy change associated with the reaction below? A → 2C

x + 2y

CO (g) can be produced by the reaction of coal with steam, as shown by the balanced equation H2O(g) + C(s) → CO(g) + H2(g). Which of the following options correctly reflect the steps required to calculate ΔH for this reaction, given the information shown below? Select all that apply. Reaction 1: H2(g) + 1212O2(g) → H2O(g); ΔH = -242.0 kJ Reaction 2: 2CO(g) → 2C(s) + O2(g) ; ΔH = +221.0 kJ

ΔH = +131.5 kJ Reaction 2 must be reversed and divided by 2.

ΔH degrees for a reaction is calculated using the equation ΣnΔHoffo(products) - ΣmΔHoffo(reactants). Which of the following statements correctly interpret this equation? Select all that apply.

ΔHoffo indicates the standard enthalpy of formation for each substance. ΔHoffo for each substance must be multiplied by the appropriate coefficient from the balanced equation. The superscript "o" indicates that the reaction takes place at 1 atm.

Which of the following correctly reflects the relationship between the heat of solution, lattice energy (symbol U), and heat of hydration?

ΔHsoln = U + ΔHhydr