AP Chemistry
6.7 Bond Enthalpies
2.7 VSEPR and Hybridization
Multi-Unit
A student investigates the thermodynamics of gas-phase hydrogenation reactions. The student compares the reaction of ethane with hydrogen to the reaction of ethyne with hydrogen, as represented by the following balanced equations:
\[ \text{Reaction 1: } \text{C}_2\text{H}_6\text{(g)} + \text{H}_2\text{(g)} \rightarrow 2\,\text{CH}_4\text{(g)} \quad \Delta H^\circ_1 = -42\text{ kJ/mol}_{\text{rxn}} \]
\[ \text{Reaction 2: } \text{C}_2\text{H}_2\text{(g)} + \text{H}_2\text{(g)} \rightarrow \text{C}_2\text{H}_4\text{(g)} \quad \Delta H^\circ_2 \]
Both reactions break \(1\text{ mol}\) of \(\text{H}-\text{H}\) bonds and form \(2\text{ mol}\) of \(\text{C}-\text{H}\) bonds per mole of reaction. Which of the following best predicts and explains the value of \(\Delta H^\circ_2\) relative to \(\Delta H^\circ_1\)?
\[ \text{Reaction 1: } \text{C}_2\text{H}_6\text{(g)} + \text{H}_2\text{(g)} \rightarrow 2\,\text{CH}_4\text{(g)} \quad \Delta H^\circ_1 = -42\text{ kJ/mol}_{\text{rxn}} \]
\[ \text{Reaction 2: } \text{C}_2\text{H}_2\text{(g)} + \text{H}_2\text{(g)} \rightarrow \text{C}_2\text{H}_4\text{(g)} \quad \Delta H^\circ_2 \]
Both reactions break \(1\text{ mol}\) of \(\text{H}-\text{H}\) bonds and form \(2\text{ mol}\) of \(\text{C}-\text{H}\) bonds per mole of reaction. Which of the following best predicts and explains the value of \(\Delta H^\circ_2\) relative to \(\Delta H^\circ_1\)?
Similar Questions
Tools for a 5
AP aligned mock tests to help you get a 5.
With grading, adaptive explanations, and more.
Find a Quiz
Find, solve, and grade every AP FRQ ever.
Find an FRQ
Stuck on AP Chemistry? Get unstuck with an AP specialist.1 to 1 tutors who know the exam inside out. Understand weeks of material in a single session.Find a Tutor
Learn AP Physics from scratch, quickly. This is the only course you'll need for the year.
A self-paced course with everything you need to get a 5. Trusted by over 15,000 students and 200+ schools. Learn fast, or we'll refund your purchase, backed by our 100% satisfaction guarantee.
Explore the Course