ch 5 practice questions Flashcards
During a chemical rxn, which of the following statements is always true?
a) a system loses energy to its surroundings
b) a system gains energy from its surroundings
c) the total energy of a system and its surroundings remains constant
d) the kinetic energy of the system equals the potential energy of the surroundings
c) the total energy of a system and its surroundings remains constant
Which of the following chemical bonds requires the most energy to break?
a) hydrogen bond
b) single bond
c) double bond
d) triple bond
d) triple bond
True or false:
In a chemical rxn, both the reactants and the products have potential energy
true
True or false:
Scientists use potential energy diagrams to describe the total energy of a system
false
(describes the energy transfer)
True or false:
Bond energies between the same atoms are similar in different molecules
true
the total amount of potential energy and kinetic energy of a substance is called…
thermal energy
True or false:
The law of conservation of energy states that the energy of a system is always 0
false
True or false:
bond energies will give an estimated value for the enthalpy of a rxn
true
True or false:
Hess’s Law states that enthalpy change is dependent on the number of steps by which a rxn occurs
false (independent)
Exothermic or endothermic?
Freezing of water
exo
Exothermic or endothermic?
combustion of acetylene gas
exo
Explain why cocoa in a thermos stays warm for hours but in a ceramic cup gets cold quickly, referring to thermal energy transfer/
The cocoa in the Thermos stays warm for hours because, unlike the ceramic cup, the
Thermos is sealed and insulated like a calorimeter, which has an insulated chamber that
minimizes energy loss to the surroundings.
Exothermic or endothermic?
temp increased
exo
