Practice Problem 4: Hess’s Law With Formation Enthalpies (4.4) - Unit 5: Energetics and Thermochemistry
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Problem 4: Hess’s Law with Formation Enthalpies

Practice - Problem 4: Hess’s Law with Formation Enthalpies

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Practice Questions

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Question 1 Easy

What does Hess's Law state?

💡 Hint: Consider how reaction energy is viewed as a state function.

Question 2 Easy

Define Standard Enthalpy of Formation.

💡 Hint: Think about how products are formed from reactants.

4 more questions available

Interactive Quizzes

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Question 1

What is Hess's Law?

A law regarding entropy changes.
A principle stating that total enthalpy change is independent of steps taken.
A method for measuring heat directly.
A concept that applies only to exothermic reactions.

💡 Hint: Think about how energy is conserved in chemical processes.

Question 2

When is the standard enthalpy of formation of an element zero?

True
False

💡 Hint: Refer to the definition of formation enthalpy.

1 more question available

Challenge Problems

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Challenge 1 Hard

Using Hess's Law, calculate the enthalpy change of forming NH₄Cl(s) from nitrogen, hydrogen, and chlorine. Given ΔH_f° for NH₄Cl(s), N₂(g), H₂(g), and Cl₂(g).

💡 Hint: Make sure to check if you need to reverse any equations!

Challenge 2 Hard

How would varying pressures and temperatures affect your calculations of ΔH using Hess's law?

💡 Hint: Reflect on how enthalpy is dependent on the conditions.

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