Chemistry

Problem

For the equilibrium 2 HI(g) ⇌ H

_2

(g) + I

_2

(g) at 700 K,

K_c = 0.016

. At

t = 30\,

s the measured concentrations are [HI] = 0.20 M, [H

_2

] = 0.040 M, and [I

_2

] = 0.040 M. Calculate

Q_c

at this moment and state whether the reaction mixture will shift toward reactants or products as it moves toward equilibrium.

Intuitive explanation

The key is to recognize that $Q_c$ is the reaction quotient—it's just like $K_c$ , but calculated with the current concentrations rather than equilibrium ones. By comparing $Q_c$ to $K_c$ , you can predict which direction the system will shift: if $Q_c$ is too large, the system has too many products and must shift left (toward reactants); if $Q_c$ is too small, it must shift right (toward products). Calculate $Q_c$ using the same expression as $K_c$ , then compare the two numbers to determine the direction.

Intuitive explanation

Browse the problem library