the reaction shifts right or toward the products when hcl is removed. which substance(s) decrease in…
the reaction shifts right or toward the products when hcl is removed. which substance(s) decrease in concentration during the shift? h₂(g) + cl₂(g) ⇌ 2hcl(g) + 184.6 j hcl h₂ and cl₂
Answer
Explanation:
Step1: Analyze Le Chatelier's Principle
When a product (HCl) is removed, the equilibrium shifts to the right (toward products) to counteract the change.
Step2: Determine Concentration Changes
In the reaction $\ce{H_{2}(g) + Cl_{2}(g) \rightleftharpoons 2HCl(g) + 184.6 J}$, as the reaction shifts right, reactants ($\ce{H_{2}}$ and $\ce{Cl_{2}}$) are consumed to form more products (HCl). Wait, no—wait, the question says HCl is removed, so the reaction shifts right (toward products), meaning we are making more HCl, but we need to see which substances decrease. Wait, no: when HCl is removed, the system tries to make more HCl, so it uses up reactants? Wait, no, the reaction is $\ce{H_{2} + Cl_{2} -> 2HCl}$. If HCl is removed, the equilibrium shifts right, so $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are converted to HCl. Wait, but the options: one is HCl, the other is $\ce{H_{2}}$ and $\ce{Cl_{2}}$. Wait, no—wait, when the reaction shifts right (toward products), the reactants are being used (their concentration decreases) and products are being made. But the question is which substance(s) decrease in concentration during the shift. Wait, the initial change is HCl removed (so HCl concentration decreases first, then the reaction shifts right). During the shift (the equilibrium adjustment), to make more HCl, the reactants $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are consumed, so their concentrations decrease? Wait, no, that can't be. Wait, no: the reaction is $\ce{H_{2} + Cl_{2} <=> 2HCl}$. If HCl is removed, the equilibrium shifts to the right (forward direction) to produce more HCl. In the forward reaction, $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are reactants, so they are used up (their concentration decreases) and HCl is produced (its concentration increases from the shift, but initially it was decreased). Wait, but the options: the first option is HCl, the second is $\ce{H_{2}}$ and $\ce{Cl_{2}}$. Wait, maybe I got it wrong. Wait, when you remove a product (HCl), the equilibrium shifts right (toward products), so the reaction proceeds forward: $\ce{H_{2} + Cl_{2} -> 2HCl}$. So during this shift, the reactants ($\ce{H_{2}}$ and $\ce{Cl_{2}}$) are consumed, so their concentrations decrease, and HCl is produced (its concentration increases, but it was initially decreased). Wait, but the question is which substance(s) decrease in concentration during the shift. So $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are reactants, so as the reaction shifts right, they are used, so their concentrations decrease. Wait, but let's re-examine. Wait, the reaction is exothermic (releases heat, 184.6 J is on the product side). But the key is Le Chatelier: remove product (HCl), shift right. So forward reaction: $\ce{H_{2} + Cl_{2} -> 2HCl}$. So in the forward reaction, $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are converted to HCl. Therefore, during the shift (forward reaction), $\ce{H_{2}}$ and $\ce{Cl_{2}}$ concentrations decrease, and HCl concentration increases (from the shift, after the initial removal). Wait, but the options: the second option is $\ce{H_{2}}$ and $\ce{Cl_{2}}$. Wait, but maybe I made a mistake. Wait, no—wait, when you remove HCl, the system tries to make more HCl, so it goes forward, using up $\ce{H_{2}}$ and $\ce{Cl_{2}}$, so their concentrations decrease. So the correct answer should be $\ce{H_{2}}$ and $\ce{Cl_{2}}$? Wait, but let's check again. Wait, the question says "Which substance(s) decrease in concentration during the shift?" The shift is to the right (toward products). So in the forward direction (shift right), reactants are consumed, so their concentrations decrease. So $\ce{H_{2}}$ and $\ce{Cl_{2}}$ are reactants, so their concentrations decrease. HCl is a product, so its concentration increases during the shift (as the reaction makes more HCl to replace what was removed). So the correct option is $\ce{H_{2}}$ and $\ce{Cl_{2}}$. Wait, but the first option is HCl. Wait, maybe I messed up. Wait, initial change: HCl is removed (so HCl concentration decreases). Then the equilibrium shifts right: the reaction proceeds forward, making HCl (so HCl concentration increases from the shift, but it was initially lower). During the shift (the process of moving to new equilibrium), the reactants are being used (so their concentration decreases) and products are being made (so their concentration increases). So the substances that decrease in concentration during the shift are the reactants, $\ce{H_{2}}$ and $\ce{Cl_{2}}$. So the correct option is the second one: $\ce{H_{2}}$ and $\ce{Cl_{2}}$.