Question

consider the reaction

2h₂ + o₂ → 2h₂o

δhᵣₓₙ = -484 kj

which answer best describes the transfer of heat that occurs when 1.70 mol h₂ reacts?

484 kj released

411 kj released

823 kj absorbed

484 kj absorbed

823 kj released

411 kj absorbed

Explanation:

Step1: Analyze the reaction formula

From \(2H_2 + O_2
ightarrow2H_2O\), \(\Delta H_{rxn}=- 484\ kJ\), it means when \(2\ mol\ H_2\) reacts, \(484\ kJ\) heat is released.

Step2: Calculate the heat change for \(1.70\ mol\ H_2\)

Set up a proportion. Let \(x\) be the heat change for \(1.70\ mol\ H_2\).
\(\frac{x}{1.70\ mol}=\frac{-484\ kJ}{2\ mol}\)
\(x=\frac{- 484\ kJ\times1.70\ mol}{2\ mol}\)
\(x=-411.4\ kJ\approx - 411\ kJ\) (negative sign indicates heat is released)

Answer:

411 kJ released