To determine how a decrease in pressure will affect the chemical equilibrium, we need to analyze the number of moles of gas on each side of the reaction:
[tex]\[ N _{2(g)} + 3 H _{2(g)} \rightleftharpoons 2 NH _{3(g)} \][/tex]
1. Count the moles of gas on each side of the reaction:
- Reactant side:
- [tex]\( N_2 \)[/tex] contributes 1 mole.
- [tex]\( 3 H_2 \)[/tex] contributes 3 moles.
- Therefore, the total number of moles on the reactant side = 1 + 3 = 4 moles.
- Product side:
- [tex]\( 2 NH_3 \)[/tex] contributes 2 moles.
- Therefore, the total number of moles on the product side = 2 moles.
2. Apply Le Chatelier's principle:
Le Chatelier's principle states that if a system at equilibrium is disturbed, the system will adjust to minimize that disturbance.
- If the pressure of the system is decreased, the system will shift the equilibrium to favor the side with more moles of gas. This is because more moles of gas will result in an increase in volume, which compensates for the decrease in pressure.
3. Based on our earlier calculation:
- The reactant side has 4 moles of gas.
- The product side has 2 moles of gas.
Because the reactant side has more moles of gas than the product side, the system will shift towards the reactant side when the pressure is decreased to counteract the change.
Therefore, the correct answer is:
- It will shift toward the reactant side because the reactant side has more moles of gas than the product side.
