Key Concepts in Thermodynamics: Bond Enthalpy and Equations

What is the rule for rounding when adding or subtracting measurements?

• Round to the least number of significant figures

• Round to the least number of decimal places

• Always round up

• Always round down

How should significant figures be handled in multiplication and division?

• Round to the highest number of significant figures

• No rounding is necessary

• Round to the least number of significant figures

• Round to the least number of decimal places

What is the sign of Delta H in an exothermic process?

• Zero

• Negative

• Cannot be determined

• Positive

What does a coffee cup calorimeter assume about the Styrofoam cup?

• It absorbs all the heat

• It is perfectly insulated

• It leaks heat slowly

• It is irrelevant to the experiment

How is Delta H calculated in calorimetry?

• Q divided by the moles of substance

• Q added to the moles of substance

• Q subtracted from the moles of substance

• Q multiplied by the moles of substance

What does the first law of thermodynamics state?

• Energy cannot be created or destroyed

• Heat lost by one substance is gained by another

• Energy is always lost as heat

• Total entropy of an isolated system can never decrease over time

What is the difference between Q and Delta H?

• Q is heat, Delta H is enthalpy change

• Q is enthalpy change, Delta H is heat

• Q and Delta H are the same

• Q is mass, Delta H is volume

What is the role of bond enthalpies in calculating Delta H of reaction?

• Sum of bonds formed minus bonds broken

• Only bonds formed are considered

• Sum of bonds broken minus bonds formed

• Only bonds broken are considered

What is the significance of the sign in Delta H calculations?

• Has no significance

• Indicates the temperature change

• Indicates direction of heat flow

• Indicates the phase change

What does the heat of formation of a pure element in its most standard state equal?

• 1

• It varies

• 0

• -1