Homework Answers

The standard enthalpy of a reaction can be ___________. 

a. calculated as the sum between the difference of the standard molar enthalpies of formation of products only.

b. calculated as the difference between the sum of the standard molar enthalpies of formation of reactants only.

c. obtained as the difference between the sum of the standard molar enthalpies of formation of products and reactants.

d. obtained from the different thermochemical equations by applying the first law of thermodynamics.

The amount of heat absorbed or released by a chemical reaction at constant atmospheric pressure. 

a. standard molar enthalpy

b. enthalpy of products

c. enthalpy of reaction

d. enthalpy

When heat flows from the system to its surroundings, heat is ________. 

a. equal

b. positive

c. negative

d. neutral

Convert 27 degrees C to F

Enthalpy of reaction is positive when _______________. 

a. chemical reaction is both endothermic and exothermic.

b. chemical reaction is endothermic.

c. the amount of heat transferred and absorbed are unequal.

d. chemical combustion does not happen.

When work is accomplished on the system, it _________ 

a. gains work and energy is denoted as positive.

b. gains energy and work is denoted as negative.

c. gains work and energy is denoted as zero.

d. gains energy and work is denoted as positive.

Explosion of a firecracker triggered by a spark is _________. 

a. exothermic

b. partly exothermic

c. both endothermic and exothermic

d. endothermic

Hess’s law applies the rule that enthalpy is an ________. 

a. extensive property.

b. intensive property.

c. extensive process.

d. intensive process

Law of Conservation of Energy states that, ______________.

a. The energy of the system and the of the surroindings are unrelated.

b. Energy can neither be created nor destroyed.

c. Energy can neither be created nor transferred.

d. The change in energy of a system is equal to the heat absorbed and released.

A calorimeter is an____________________. 

a. insulated coffee cup that that transfers an immense amount of heat.

b. excellent insulator that works without a thermometer.

c. insulated apparatus that contains water or any liquid of known heat capacity.

d. apparatus that has water or any liquid with unknown heat capacity.

Thermal decomposition of limestone to form calcium oxide and carbon dioxide is ________. 

a. exothermic

b. endothermic

c. both endothermic and exothermic

d. partly exothermic

The first law of thermodynamics hints that __________. 

a. net energy flow to or from any surroundings comes in either heat or work.

b. net heat flow to or from any system comes in either energy or work.

c. net energy flow to or from any system comes from the surroundings.

d. net energy flow to or from any system comes in either heat or work.

Hess’s law states that the __________________. 

a. enthalpy of a sum of a series of reactions is unequal to the sum of the enthalpies of those two reactions.

b. enthalpy of a sum of a series of reactions is equal to the sum of the enthalpies of those two reactions.

c. enthalpy of a sum of a series of reactions is equal to the sum of the heat capacities of those two reactions.

d. enthalpy of a sum of two reactions is equal to the difference of the enthalpies of those two reactions.

Heat is a form energy transfer between objects as an effect of their difference in _________.

a. temperature

b. volume

c. energy

d. pressure

Hess’s law applies the rule that enthalpy is an ________.

a. extensive process.

b. intensive property.

c. intensive process

d. extensive property.

The heat capacity of a substance is determined ______________.

a. by a constant specific heat values regardless of physical states.

c. through careful measure of specific heat values.

c. through calorimetry.

d. by increasing the temperature by 1°C.

Hess’s law states that the __________________.

a. enthalpy of a sum of a series of reactions is equal to the sum of the enthalpies of those two reactions.

b. enthalpy of a sum of two reactions is equal to the difference of the enthalpies of those two reactions.

c. enthalpy of a sum of a series of reactions is equal to the sum of the heat capacities of those two reactions.

d. enthalpy of a sum of a series of reactions is unequal to the sum of the enthalpies of those two reactions.

Heat is a form energy transfer between objects as an effect of their difference in _________.

a. volume

b. energy

c. pressure

d. temperature

Calorimetry involves the measurement of the ___________________.

a. quantity of heat exchanged between a system and the surroundings.

b. quantity of work exchanged between a systems.

c. quantity of work exchanged between a system and the surroundings.

d. quantity of heat exchanged between the systems.

Explosion of a firecracker triggered by a spark is _________.

a. endothermic

b. exothermic

c. partly exothermic

d. both endothermic and exothermic

Enthalpy of reaction is positive when _______________.

a. chemical reaction is endothermic.

b. chemical reaction is both endothermic and exothermic.

c. chemical combustion does not happen.

d. the amount of heat transferred and absorbed are unequal.

Law of Conservation of Energy states that, ______________.

a. Energy can neither be created nor destroyed.

b. The change in energy of a system is equal to the heat absorbed and released.

c. The energy of the system and the of the surroindings are unrelated.

d. Energy can neither be created nor transferred.

The most stable conformation of butane is anti conformation and it's least stable conformation is eclipsed conformation. Why?

When work is accomplished on the system, it _________

a. gains work and energy is denoted as positive.

b. gains energy and work is denoted as positive.

c. gains work and energy is denoted as zero.

d. gains energy and work is denoted as negative.

A calorimeter is an____________________.

a. apparatus that has water or any liquid with unknown heat capacity.

b. insulated coffee cup that that transfers an immense amount of heat.

c. excellent insulator that works without a thermometer.

d. insulated apparatus that contains water or any liquid of known heat capacity.

The study of energy and heat flow that goes with a chemical reaction and physical transformation.

a. Thermodynamics

b. Enthalpy

c. Conservation of Energy

d. Thermochemistry