Hess's Law

Determine the H for reaction of this equation: 3C (graphite) + 4 H2(g) --> C3H8(g)

using these intermediates:

(A) C₃H₈ (g) + 5O₂(g) --> 3CO₂ (g) + 4H₂O (l) H= -2219.9 kJ

(B) C(graphite) + O₂(g) --> CO₂ (g) H= -393.5 kJ

(C) H₂ (g) + 1/2 O₂ (g) --> H₂O (l) H= -285.8 kJ

• -683.4 kJ

• -2899.2 kJ

• -1324.7 kJ

• -104.0 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

What is the Delta H if you reverse the reaction.

• 86 kJ

• - 86 kJ

• 68 kJ

• -68 kJ

Tags

NGSS.HS-PS1-4

According to Hess' Law, if you double the coefficients of a reaction, ΔH will ________________________

• Stay the same

• Double

• Quadruple

• Halve

Tags

NGSS.HS-PS1-4

Determine the \( \Delta H \) for the reaction: \( \ce{2H2(g) + O2(g) -> 2H2O(l)} \) using these intermediates: (A) \( \ce{H2(g) + 1/2O2(g) -> H2O(l)} \) \( \Delta H = -285.8 \text{ kJ} \) (B) \( \ce{H2O(l) -> H2(g) + 1/2O2(g)} \) \( \Delta H = 285.8 \text{ kJ} \)

• -571.6 kJ

• -285.8 kJ

• 0 kJ

• 571.6 kJ

Tags

NGSS.HS-PS1-4

Hess's Law is based on which fundamental principle of thermodynamics?

• First Law of Thermodynamics

• Second Law of Thermodynamics

• Third Law of Thermodynamics

• Zeroth Law of Thermodynamics

If a reaction is reversed, according to Hess's Law, what happens to \( \Delta H \)?

• It stays the same

• It doubles

• It changes sign

• It halves

Which of the following is a real-world application of Hess's Law?

• Calculating the energy required to melt ice

• Determining the energy change in a battery

• Measuring the temperature of a substance

• Predicting the color change in a reaction

Tags

NGSS.HS-PS3-1

In an experiment, the enthalpy change for the combustion of methane is measured. Which equation represents this process?

• \( \ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)} \)

• \( \ce{CH4(g) -> C(s) + 2H2(g)} \)

• \( \ce{CH4(g) + H2O(g) -> CO(g) + 3H2(g)} \)

• \( \ce{CH4(g) + Cl2(g) -> CH3Cl(g) + HCl(g)} \)

Tags

NGSS.HS-PS1-4

According to Hess's Law, the enthalpy change of a reaction depends on:

• The initial and final states only

• The path taken by the reaction

• The speed of the reaction

• The temperature at which the reaction occurs

Tags

NGSS.HS-PS1-4

Which of the following reactions can be used to demonstrate Hess's Law?

• Combustion of hydrogen

• Formation of water from hydrogen and oxygen

• Decomposition of calcium carbonate

• All of the above

Tags

NGSS.HS-PS3-1