Questions and Answers
What does the law of conservation of energy state?
Energy cannot be created or destroyed.
A chemical reaction requires 31.39 kJ. How many kilocalories does this correspond to?
7.502 kCal
A chemical reaction releases 55.2 kcal. How many kilojoules does this correspond to?
231 kJ
Which bond is the strongest?
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Which bond is the weakest?
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In a(n) _____ reaction, the products are higher in energy than the reactants.
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In the reaction C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), the bonds formed in the products are stronger than the bonds broken in the reactants.
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How many kilojoules are released when 3.5 mol of C2H4 reacts in the reaction C2H4(g) + H2(g) → C2H6(g) with ΔH = -137 kJ?
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How many kilojoules are released when 55.3 g of C2H4 reacts in the reaction C2H4(g) + H2(g) → C2H6(g) with ΔH = -137 kJ?
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What is the activation energy of a chemical reaction?
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Which ripens faster?
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Which will increase the reaction rate?
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What is a catalyst?
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A catalyst lowers the activation energy of a chemical reaction.
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The rate of any chemical reaction can be determined by observing the amount of product formed per unit of [x].
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In any chemical reaction, the rate of the reaction can be increased by [x] the temperature and [x] the concentration of reactant molecules.
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A reaction that can proceed in either the forward or the reverse direction as written is called a ________ reaction.
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A chemical reaction has reached equilibrium when the rate of the forward reaction [x] the rate of the reverse reaction.
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At equilibrium, the concentrations of the reactants and products are always equal.
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An equilibrium constant Kc = 1 × 10^7 for a reaction indicates that the reaction favors product formation.
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If the equilibrium constant for a reaction is 1 × 10^-5, this means that the equilibrium mixture contains mostly reactants.
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If the concentration of NO(g) and NOBr(g) are both 0.50 M, at equilibrium, what is the concentration of Br2(g) for the reaction 2NO(g) + Br2(g) ⇌ 2NOBr(g) with Kc = 0.60?
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For the equilibrium reaction CO(g) + 2H2(g) ⇌ CH3OH(g) + heat, which cause and effect are correctly matched?
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For the reaction N2(g) + O2(g) ⇌ 2NO(g), if the volume of the container is decreased, what will happen to the amount of NO present?
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Study Notes
Law of Conservation of Energy
- Energy cannot be created or destroyed, only transformed.
Energy Units Conversion
- A chemical reaction releasing 31.39 kJ corresponds to approximately 7.502 kCal.
- A reaction releasing 55.2 kCal corresponds to approximately 231 kJ.
Bond Strength
- The strongest bond among H-Br, H-Cl, H-F, and H-I is H-F.
- The weakest bond is H-I.
Types of Reactions
- In endothermic reactions, products have higher energy than reactants.
Reaction Enthalpy
- For the combustion of propane (C3H8), ΔH = -531 kcal/mol indicates that stronger bonds are formed in the products compared to bonds broken in reactants.
- The reaction of C2H4 with H2 releases 480 kJ when 3.5 mol of C2H4 reacts (ΔH = -137 kJ).
- When 55.3 g of C2H4 reacts, approximately 270 kJ are released.
Activation Energy
- The activation energy is the energy required to initiate a chemical reaction.
Factors Affecting Reaction Rate
- A banana ripens faster on the countertop compared to being stored in the refrigerator.
- Reaction rates can increase by:
- Increasing the concentration of reactants
- Properly aligning reactants during collisions
- Adding a catalyst
- Increasing temperature
- A catalyst speeds up a reaction and lowers activation energy without being consumed.
Measuring Reaction Rate
- The rate can be determined by observing the amount of product formed per unit of time.
- Increasing temperature and concentration both increase reaction rates.
Reversible Reactions and Equilibrium
- A reversible reaction can proceed in either direction.
- At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction.
- Concentrations of reactants and products at equilibrium are not necessarily equal.
Equilibrium Constant (Kc)
- A Kc value of 1 × 10^7 indicates a strong favor for product formation.
- Kc value of 1 × 10^-5 indicates that reactants are favored.
- For the reaction 2NO + Br2 ⇌ 2NOBr, with NO and NOBr at 0.50 M each, the Br2 concentration at equilibrium is found to be 1.7 M.
Shift in Equilibrium
- In the equilibrium reaction of CO + 2H2 ⇌ CH3OH + heat, removing H2 will shift the equilibrium to the left.
- Decreasing the volume of the container for the reaction N2 + O2 ⇌ 2NO does not change the amount of NO present at equilibrium.
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Test your knowledge with these flashcards focused on key concepts from Chemistry Homework 7. This quiz covers the law of conservation of energy, conversions between energy units, and bond strength. Challenge yourself and enhance your understanding of chemistry!
