Mod 6 - EBs with rxns

Question 1

T/F: If Delta(H_hat) is -ve, then rxn is endothermic

Answer 1

FALSE: rxn is exothermic. E removed from reactor to keep temp from increasing

Question 2

T/F: If Delta(H_hat) is +ve, then rxn is endothermic

Answer 2

TRUE: E added to reactor to keep temp from decreasing

Question 3

T/F: Typically, reactors can handle the E changes occurring in the system without requiring substantial heating or cooling to maintain steady state.

Answer 3

FALSE

Question 4

T/F: To calculate the change in enthalpy that occurs due to a chemical rxn, specific heats of rxn must be combined with extent of rxn.

Answer 4

TRUE

Question 5

T/F: Specific heat of rxn is the enthalpy change for a process in which stoichiometric quantities or reactants react completely to form products at const. T&P

Answer 5

TRUE

Question 6

T/F: St. heat of rxn is specified for reactants and products at st. T&P cond’t

Answer 6

TRUE

Question 7

T/F: A calorimeter measures the heat of rxn equivalent to digesting a meal in the human intestinal tract.

Answer 7

FALSE

Question 8

T/F: Heats of rxn may be measured in a calorimeter. which is a closed reactor submersed in a fluid and enclosed in an insulated vessel, and where the increase or decrease in fluid temp determines the amount of E released or absorbed during a rxn.

Answer 8

TRUE

Question 9

T/F: The calorimeter can be used to estimate the heat of rxn to form CO from solid C and diatomic O2

Answer 9

FALSE

Question 10

T/F: Hess’s Law says that math can be applied to estimate heats of form.

Answer 10

FALSE: algebra can be applied to estimate heats of reaction, but not heats of form if they’re not equivalent

Question 11

T/F: At low/moderate pressure, deltaH(hat)r is nearly independent of pressure. (deltaH(hat)r(T,P) = deltaH(hat)r(T))

Answer 11

TRUE

Question 12

T/F: Heats of combustion table has values listed for the complete formation of the substance

Answer 12

FALSE: Heats of reaction does, which is why we include extent of reaction - deltaH(dot) = extent(dot)*deltaH(hat)r

Question 13

T/F: Value of heat of rxn depends on phase of the reactants, but not the products.

Answer 13

TRUE: depends on phase of both!

Question 14

T/F: There is no difference between deltaH(hat)(T,P) and deltaH(hat)º

Answer 14

FALSE: Superscript “ º “ means heat of rxn is at standard temp and press cond’t (25ºC and 1atm), which means the amount of heat that must be added/removed to keep @ these cond’t

Question 15

T/F: The standard heat of reaction is preferred when all elements are in st. cond’t (25ºC and 1atm)

Answer 15

FALSE: you can use either method but standard heat of FORMATION is generally more efficient when the reagents are in st. cond’t of 25ºC and 1 atm (B.1)

Question 16

T/F: st. heat of combustion = enthalpy associated with the complete combustion of one mole of substance at 25ºC and 1 atm

Answer 16

TRUE

Question 17

T/F: The st. heat of combustion will always be the opposite sign and value to the st. heat of formation (hint: look at B.1)

Answer 17

FALSE: same sign, but not same value

Question 18

T/F: It is not necessary to draw a PFD in your solution or define your reference states

Answer 18

FALSE: Although PFD not necessary, clearly defining reference states ARE necessary

Question 19

T/F: Heats of reaction is a more direct method of obtaining the enthalpy of the entire reaction (moving horizontally through the reaction equation) while heats of formation looks at the enthalpy associated with each component in the system

Answer 19

TRUE: Enthalpy of formation looks at the enthalpy of reaction for each component of the system (branching off the beaten path, sort of looks like a family tree or a wack-ass pyramid scheme)

Question 20

T/F: Dealing with a single reaction for which deltaH(hat)rº is known = heat of form more preferred

Answer 20

FALSE: heat of rxn more preferred (can be calculated through Hess or

Question 21

T/F: The heat of formation method is ideal for multiple reactions or for single reactions for which deltaH(hat)rº is unknown

Answer 21

TRUE

Question 22

T/F: For heats of form, the reference state is that of all elements constituting the reactants and products at 25ºC and 1 atm

Answer 22

TRUE