Question

the reaction shifts left or toward the reactants when hcl is added. which substance(s) increase in concentration during the shift? h₂(g) + cl₂(g) ⇌ 2hcl(g) + 184.6 j h₂ and cl₂ hcl

Explanation:

Step1: Analyze Le Chatelier's Principle

When a stress (like adding a product) is applied to an equilibrium system, the system shifts to counteract the stress. Here, adding HCl (a product) shifts the reaction left (toward reactants).

Step2: Determine Concentration Changes

A left shift means reactants ($\ce{H2}$ and $\ce{Cl2}$) are formed from products ($\ce{HCl}$). So their concentrations increase, while $\ce{HCl}$ concentration decreases.

Answer:

$\ce{H2}$ and $\ce{Cl2}$