Chemistry chapter 6 smartbook

Calculate the standard enthalpy change for the reaction SiO2 (s) + 4HF (g) → SiF4 (g) + 2H2O (l) given the information in the table below.

-183.6 kJ

Gas Aqueous Solution Pure Substance

1 atm 1 M Stable forces at the given temperature and atm of preesure

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

1, elements, standard

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

1/2 N2 (g) + 3/2 H 2 (g) = NH3 (g)

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 3232A → C?

1/2x - y

Calculate ΔH°rxn for the reaction A + 2B → 2C using the ΔH°f values given below.

2(c) - (a) - 2(b)

Consider the following formation reactions. 12O2 (g) + H2 (g) → H2O(g)12O2 (g) + H2 (g) → H2O(g) 12H2(g) + 12Cl2 (g) → HCl (g)12H2(g) + 12Cl2 (g) → HCl (g) Using Hess's law, select the correct forms of the formation equations that will add up to the reaction below. 2H2O(g) + 2Cl2 (g) → O2 (g) + 4HCl (g)

2H2(g) + 2Cl2 (g) → 4HCl (g)2H2(g) + 2Cl2 (g) → 4HCl (g) 2H2O(g) → O2 (g) + 2H2 (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

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) Rxn 1 + 2(Rxn 2) (-Rxn 1) + (-Rxn 2)

A + B = 3C A = 2B B + C = A

Match the two figures (A and B) correctly with the terms "exothermic" and "endothermic."

A - Exothermic B - Endothermic

The internal energy change for a reaction is related to enthalpy by equation ΔE = ΔH - PΔV. This equation tells us that ΔH is very close to ΔE if there is no volume change in the reaction. In which of the following situations would ΔH give a good approximation of ΔE? Select all that apply.

A reaction in which the change in the number of moles of gas present is zero A reaction involving only solids and liquids

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

A → B B → 2C

Which of the following statements correctly describe exothermic and endothermic reactions? Select all that apply.

An exothermic reaction is one that releases heat to its surroundings. If the container of a reaction becomes colder during the reaction, the reaction is endothermic. The reactants in an endothermic reaction are lower in energy than the products.

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

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

Which of the following is the correct enthalpy diagram for the decomposition of dinitrogen pentoxide, represented by the balanced equation 2N2O5 (g) + 447.4 kJ → 4NO (g) + 3O2 (g)?

B

Two equations must be manipulated in order to generate the overall equation Br2 + 2NO → 2NOBr. Select the two chemical equations from below that can be arranged and added together to generate the overall equation. (Note: the equation(s) may need to be reversed or multiplied by a constant.)

Br2 + NO → NOBr2 2NOBr → NOBr2 + NO

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)

Two equations must be manipulated in order to generate the overall equation A + 2B → D. Select the two chemical equations from below that can be arranged and added together to generate the overall equation. (Note: the equation(s) may need to be reversed or multiplied by a constant.)

D → C + B A + B → C

Which of the following symbols is used to indicate internal energy?

E

True or false: If an ice cube is placed on a hot stove, heat transfers from the ice cube to the stove.

False

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

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

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

Hess

The SI unit of energy is the ______, which is abbreviated by the symbol _______________

Joule, J

An experiment is developed to determine the energy change during a precipitation reaction, represented by the following balanced equation: AgCH3COO (aq) + NaCl (aq) → NaCH3COO (aq) + AgCl (s) Which of the following are part of the system? Select all that apply.

NaCl AgCH3COO

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)

Which of the following statements correctly describe the two reactions outlined below? Select all that apply. Reaction 1: A → B ΔH = +50 kJ Reaction 2: C → D ΔH = -100 kJ

Reaction 2 is exothermic. Reaction 2 releases twice as much energy as Reaction 1 absorbs. The surroundings near Reaction 1 will become colder as it proceeds.

Which of the following options describe an enthalpy diagram correctly? Select all that apply.

The arrow in the enthalpy diagram points from reactants to products. The direction of the arrow in an enthalpy diagram indicates whether a reaction is exothermic or endothermic. Enthalpy, H, increases up the y-axis. In an endothermic reaction, the reactants will be at the bottom of the enthalpy diagram.

ΔHrxn ΔHorxn ΔHof

The change in enthalpy for a given reaction The enthalpy change of a reaction measured at the standard state The enthalpy change when 1 mol of a compound forms from its elements in their standard states

Hot coffee is poured into a mug. It slowly cools, releasing heat to the environment. If we consider the coffee to be the system, which of the following are part of the surroundings? Select all that apply.

The table underneath the mug The mug The air in the room

If a system gains heat as it does work on its surroundings, the total change in internal energy will _____.

be positive, negative, or zero

By definition, the standard enthalpy of formation of a pure_____________in its standard state is wqual to 0 kJ/mol

element

The term _____ indicates that heat is absorbed by the system from the surroundings, while _____ indicates that heat is released by the system into the surroundings.

endothermic; exothermic

The first law of thermodynamics states that the total amount of_______ in the universe remains constant

energy

A thermochemical equation links a reaction's stoichiometry to its_______change or ΔHrxn.

enthalpy

In a thermochemical equation, the _____ change is always written next to the balanced chemical equation.

enthalpy

Based on the first law of thermodynamics, the energy gained by a system is _____ the energy lost by the surroundings.

equal to

When ΔH for a thermochemical equation is negative, that reaction is _____, while a positive value for ΔH is associated with an _____ reaction.

exothermic ; endothermic

ΔH will be equal to ΔE if the total number of moles of____________does not change during a chemical reaction (discounting any small volume change caused by liquids or solids).

gas

The total change in the internal energy of a system is the sum of the energy transferred as______and/or_________

heat, work

In the enthalpy diagram shown, the reactants are _____ in energy than the products. The reaction therefore _____ heat and is _____.

higher; releases; exothermic

The sum of all the potential and kinetic energies for all particles in a system is called the total______________energy (E) of the system

internal

The change in enthalpy (ΔH) is equal to the change in heat (q) when the system is at constant _____.

pressure

The symbol _____ always indicates heat (or thermal energy), which is transfered as a result of a difference in temperature between a system and its surroundings.

q

Thermodynamic parameters are usually calculated for compounds under_________conditions, since values tend to vary somewhat with conditions. To be in this state, a gas must have a pressure of 1_______________and a solution must have a concentration of 1___________________

standard, atm, molar

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

The study of heat changes in chemical reactions is called___________

thermochemistry

The study of energy and its transformations is called ______.

thermodynamics

True or false: Both heat and work can be measured in joules.

true

Work Heat Internal Energy

w q e

Energy transferred when an object is moved by a force results in____________being done on that object.

work

Which of the following relationships are true? Select all that apply.

ΔE = q + w (under any conditions) ΔH = q (at constant P) ΔE = ΔH + w (at constant P)