Let's consider the given equilibrium reaction:
[tex]\[ 4 \text{HCl} + \text{O}_2 \rightleftharpoons 2 \text{H}_2\text{O} + \text{Cl}_2 \][/tex]
We are asked to analyze the effect of increasing the concentration of [tex]\( \text{H}_2\text{O} \)[/tex] on this equilibrium system.
### Step-by-Step Analysis:
1. Le Chatelier's Principle:
Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium will move to counteract the change. This means if we increase the concentration of one of the products, the system will try to oppose this change by shifting the equilibrium to the left, towards the reactants.
2. Effect of Increasing [tex]\( \text{H}_2\text{O} \)[/tex]:
By increasing the concentration of [tex]\( \text{H}_2\text{O} \)[/tex], we are adding more product to the system. According to Le Chatelier's principle, the equilibrium will shift to the left (towards the reactants) to reduce the increased concentration of [tex]\( \text{H}_2\text{O} \)[/tex].
3. Impact on Reaction Rates:
- Backward Reaction Rate: As the equilibrium shifts to the left, the rate of the backward reaction (where products convert back into reactants) will increase. This is to use up the excess [tex]\( \text{H}_2\text{O} \)[/tex] and produce more [tex]\( \text{HCl} \)[/tex] and [tex]\( \text{O}_2 \)[/tex].
- Forward Reaction Rate: As the system initially shifts towards the reactants to counteract the addition of [tex]\( \text{H}_2\text{O} \)[/tex], the forward reaction rate will not increase as this would make the issue worse.
4. Concentrations of Other Species:
- Hydrochloric Acid ([tex]\(\text{HCl}\)[/tex]): As the equilibrium shifts to the left, the concentration of [tex]\( \text{HCl} \)[/tex] will increase as it’s being produced from the backward reaction.
- Chlorine ([tex]\(\text{Cl}_2\)[/tex]): As the equilibrium shifts to the left, the concentration of [tex]\( \text{Cl}_2 \)[/tex] will decrease because it is being used up to form more reactants.
After analyzing these points, the immediate and correct effect of increasing the concentration of [tex]\( \text{H}_2\text{O} \)[/tex] is that the rate of the backward reaction increases.
### Conclusion:
The correct result from increasing the concentration of [tex]\( \text{H}_2\text{O} \)[/tex] is:
- The rate of the backward reaction increases.
Therefore, the answer to the question is the first option:
The rate of the backward reaction increases.
