Explain Bond Energy Changes - Chemistry
Card 1 of 30
What is the relationship between bond length and bond strength (general trend)?
What is the relationship between bond length and bond strength (general trend)?
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Shorter bonds are generally stronger. Increased electron sharing creates shorter, stronger bonds.
Shorter bonds are generally stronger. Increased electron sharing creates shorter, stronger bonds.
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Identify the correct statement about temperature change in an exothermic reaction in a closed calorimeter.
Identify the correct statement about temperature change in an exothermic reaction in a closed calorimeter.
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Temperature of the surroundings increases. Energy released heats the surrounding environment.
Temperature of the surroundings increases. Energy released heats the surrounding environment.
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At what point on a potential energy vs. bond distance curve is a bond most stable?
At what point on a potential energy vs. bond distance curve is a bond most stable?
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At the minimum of the curve (equilibrium distance). Minimum energy corresponds to most stable bond configuration.
At the minimum of the curve (equilibrium distance). Minimum energy corresponds to most stable bond configuration.
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Which term is positive in a bond-enthalpy calculation: breaking bonds or forming bonds?
Which term is positive in a bond-enthalpy calculation: breaking bonds or forming bonds?
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Breaking bonds (energy input). Energy input needed, so breaking contributes positive value.
Breaking bonds (energy input). Energy input needed, so breaking contributes positive value.
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What is the sign of $\Delta H$ if products have lower enthalpy than reactants?
What is the sign of $\Delta H$ if products have lower enthalpy than reactants?
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$\Delta H < 0$. Lower product enthalpy means energy was released overall.
$\Delta H < 0$. Lower product enthalpy means energy was released overall.
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Find $\Delta H$ if $\sum E(\text{broken})=1500$ and $\sum E(\text{formed})=1500$ in $\text{kJ mol}^{-1}$.
Find $\Delta H$ if $\sum E(\text{broken})=1500$ and $\sum E(\text{formed})=1500$ in $\text{kJ mol}^{-1}$.
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$\Delta H \approx 0\ \text{kJ mol}^{-1}$. Equal energies broken and formed give no net change.
$\Delta H \approx 0\ \text{kJ mol}^{-1}$. Equal energies broken and formed give no net change.
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What is the sign of $\Delta H$ if products have higher enthalpy than reactants?
What is the sign of $\Delta H$ if products have higher enthalpy than reactants?
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$\Delta H > 0$. Higher product enthalpy means energy was absorbed overall.
$\Delta H > 0$. Higher product enthalpy means energy was absorbed overall.
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Identify whether this statement is correct: "Bond formation requires energy input."
Identify whether this statement is correct: "Bond formation requires energy input."
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Incorrect; bond formation releases energy. Bond formation is always exothermic (energy releasing).
Incorrect; bond formation releases energy. Bond formation is always exothermic (energy releasing).
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Identify whether this statement is correct: "Bond breaking releases energy."
Identify whether this statement is correct: "Bond breaking releases energy."
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Incorrect; bond breaking absorbs energy. Bond breaking is always endothermic (energy absorbing).
Incorrect; bond breaking absorbs energy. Bond breaking is always endothermic (energy absorbing).
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Find $\Delta H$ if $\sum E(\text{broken})=800$ and $\sum E(\text{formed})=950$ in $\text{kJ mol}^{-1}$.
Find $\Delta H$ if $\sum E(\text{broken})=800$ and $\sum E(\text{formed})=950$ in $\text{kJ mol}^{-1}$.
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$\Delta H \approx -150\ \text{kJ mol}^{-1}$. Using $\Delta H = 800 - 950 = -150$ from formula.
$\Delta H \approx -150\ \text{kJ mol}^{-1}$. Using $\Delta H = 800 - 950 = -150$ from formula.
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Find $\Delta H$ if $\sum E(\text{broken})=1200$ and $\sum E(\text{formed})=900$ in $\text{kJ mol}^{-1}$.
Find $\Delta H$ if $\sum E(\text{broken})=1200$ and $\sum E(\text{formed})=900$ in $\text{kJ mol}^{-1}$.
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$\Delta H \approx +300\ \text{kJ mol}^{-1}$. Using $\Delta H = 1200 - 900 = +300$ from formula.
$\Delta H \approx +300\ \text{kJ mol}^{-1}$. Using $\Delta H = 1200 - 900 = +300$ from formula.
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Classify the reaction if $\sum E(\text{broken})=500$ and $\sum E(\text{formed})=700$.
Classify the reaction if $\sum E(\text{broken})=500$ and $\sum E(\text{formed})=700$.
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Exothermic. More energy formed than broken gives negative $\Delta H$.
Exothermic. More energy formed than broken gives negative $\Delta H$.
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Classify the reaction if $\sum E(\text{broken})=650$ and $\sum E(\text{formed})=400$.
Classify the reaction if $\sum E(\text{broken})=650$ and $\sum E(\text{formed})=400$.
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Endothermic. More energy broken than formed gives positive $\Delta H$.
Endothermic. More energy broken than formed gives positive $\Delta H$.
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Choose the correct sign: If more energy is released forming bonds than absorbed breaking bonds, $\Delta H$ is what?
Choose the correct sign: If more energy is released forming bonds than absorbed breaking bonds, $\Delta H$ is what?
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$\Delta H < 0$. Net energy release makes reaction exothermic.
$\Delta H < 0$. Net energy release makes reaction exothermic.
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Choose the correct sign: If more energy is absorbed breaking bonds than released forming bonds, $\Delta H$ is what?
Choose the correct sign: If more energy is absorbed breaking bonds than released forming bonds, $\Delta H$ is what?
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$\Delta H > 0$. Net energy absorption makes reaction endothermic.
$\Delta H > 0$. Net energy absorption makes reaction endothermic.
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Identify $\Delta H$ sign if products are more stable (lower potential energy) than reactants.
Identify $\Delta H$ sign if products are more stable (lower potential energy) than reactants.
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$\Delta H < 0$. Lower energy products indicate exothermic reaction.
$\Delta H < 0$. Lower energy products indicate exothermic reaction.
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Identify $\Delta H$ sign if products are less stable (higher potential energy) than reactants.
Identify $\Delta H$ sign if products are less stable (higher potential energy) than reactants.
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$\Delta H > 0$. Higher energy products indicate endothermic reaction.
$\Delta H > 0$. Higher energy products indicate endothermic reaction.
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Which option indicates a stronger bond: bond energy $350$ or $600\ \text{kJ mol}^{-1}$?
Which option indicates a stronger bond: bond energy $350$ or $600\ \text{kJ mol}^{-1}$?
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$600\ \text{kJ mol}^{-1}$. Higher bond energy indicates stronger bond requiring more energy.
$600\ \text{kJ mol}^{-1}$. Higher bond energy indicates stronger bond requiring more energy.
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Which option indicates a weaker bond: bond energy $200$ or $450\ \text{kJ mol}^{-1}$?
Which option indicates a weaker bond: bond energy $200$ or $450\ \text{kJ mol}^{-1}$?
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$200\ \text{kJ mol}^{-1}$. Lower bond energy indicates weaker bond requiring less energy.
$200\ \text{kJ mol}^{-1}$. Lower bond energy indicates weaker bond requiring less energy.
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Identify the correct expression for energy released by bond formation in a reaction.
Identify the correct expression for energy released by bond formation in a reaction.
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$\sum E(\text{bonds formed})$ (released). Energy released when bonds form during reaction.
$\sum E(\text{bonds formed})$ (released). Energy released when bonds form during reaction.
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What does it mean if a reaction has $\Delta H = -250\ \text{kJ mol}^{-1}$?
What does it mean if a reaction has $\Delta H = -250\ \text{kJ mol}^{-1}$?
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$250\ \text{kJ mol}^{-1}$ is released to the surroundings. Negative $\Delta H$ means system releases energy to surroundings.
$250\ \text{kJ mol}^{-1}$ is released to the surroundings. Negative $\Delta H$ means system releases energy to surroundings.
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What does it mean if a reaction has $\Delta H = +120\ \text{kJ mol}^{-1}$?
What does it mean if a reaction has $\Delta H = +120\ \text{kJ mol}^{-1}$?
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$120\ \text{kJ mol}^{-1}$ is absorbed from the surroundings. Positive $\Delta H$ means system absorbs energy from surroundings.
$120\ \text{kJ mol}^{-1}$ is absorbed from the surroundings. Positive $\Delta H$ means system absorbs energy from surroundings.
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Which term is positive in a bond-enthalpy calculation: breaking bonds or forming bonds?
Which term is positive in a bond-enthalpy calculation: breaking bonds or forming bonds?
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Breaking bonds (energy input). Energy input needed, so breaking contributes positive value.
Breaking bonds (energy input). Energy input needed, so breaking contributes positive value.
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Which term is treated as negative in a bond-enthalpy calculation: breaking bonds or forming bonds?
Which term is treated as negative in a bond-enthalpy calculation: breaking bonds or forming bonds?
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Forming bonds (energy released). Energy released, so forming contributes negative value.
Forming bonds (energy released). Energy released, so forming contributes negative value.
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Identify the correct statement about temperature change in an exothermic reaction in a closed calorimeter.
Identify the correct statement about temperature change in an exothermic reaction in a closed calorimeter.
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Temperature of the surroundings increases. Energy released heats the surrounding environment.
Temperature of the surroundings increases. Energy released heats the surrounding environment.
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Identify the correct statement about temperature change in an endothermic reaction in a closed calorimeter.
Identify the correct statement about temperature change in an endothermic reaction in a closed calorimeter.
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Temperature of the surroundings decreases. Energy absorbed cools the surrounding environment.
Temperature of the surroundings decreases. Energy absorbed cools the surrounding environment.
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Choose the correct comparison: For an exothermic reaction, is $E_a$ usually greater than, less than, or unrelated to $|\Delta H|$?
Choose the correct comparison: For an exothermic reaction, is $E_a$ usually greater than, less than, or unrelated to $|\Delta H|$?
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Unrelated; $E_a$ and $|\Delta H|$ are independent. Activation energy is independent of reaction enthalpy change.
Unrelated; $E_a$ and $|\Delta H|$ are independent. Activation energy is independent of reaction enthalpy change.
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Identify what a catalyst changes: $\Delta H$, $E_a$, or both?
Identify what a catalyst changes: $\Delta H$, $E_a$, or both?
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$E_a$ only (it lowers $E_a$). Catalysts only affect reaction pathway, not energy change.
$E_a$ only (it lowers $E_a$). Catalysts only affect reaction pathway, not energy change.
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In an endothermic reaction, are products at higher or lower enthalpy than reactants?
In an endothermic reaction, are products at higher or lower enthalpy than reactants?
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Higher enthalpy than reactants. Energy absorbed makes products less stable than reactants.
Higher enthalpy than reactants. Energy absorbed makes products less stable than reactants.
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In an exothermic reaction, are products at higher or lower enthalpy than reactants?
In an exothermic reaction, are products at higher or lower enthalpy than reactants?
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Lower enthalpy than reactants. Energy released makes products more stable than reactants.
Lower enthalpy than reactants. Energy released makes products more stable than reactants.
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