Which reaction will produce more product when pressure is increased? A) 2HgO(s) -> 2Hg(l) + O2(g) B) N2(g) + 3H2(g) <=> 2NH3(g) C) CaCO3(s) <=> CaO(s) + CO2(g)

This question applies Le Chatelier's Principle, which states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. For pressure changes, this principle applies to reactions involving gases. An increase in pressure will shift the equilibrium towards the side with fewer moles of gas.

Let's analyze each option:

• A) $2\text{HgO(s)} \rightarrow 2\text{Hg(l)} + \text{O}_2\text{(g)}$

  • Reactant side: 0 moles of gas (solid)
  • Product side: 1 mole of gas ($\text{O}_2$)
  • An increase in pressure will shift the equilibrium to the left (reactant side), producing less product.

• B) $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}$

  • Reactant side: $1 \text{ mole of N}_2 + 3 \text{ moles of H}_2 = 4$ moles of gas
  • Product side: $2 \text{ moles of NH}_3 = 2$ moles of gas
  • An increase in pressure will shift the equilibrium to the right (product side), which has fewer moles of gas. This will produce more product ($\text{NH}_3$).

• C) $\text{CaCO}_3\text{(s)} \rightleftharpoons \text{CaO(s)} + \text{CO}_2\text{(g)}$

  • Reactant side: 0 moles of gas (solid)
  • Product side: 1 mole of gas ($\text{CO}_2$)
  • An increase in pressure will shift the equilibrium to the left (reactant side), producing less product.

• D) $\text{H}_2\text{(g)} + \text{Cl}_2\text{(g)} \rightleftharpoons 2\text{HCl(g)}$

  • Reactant side: $1 \text{ mole of H}_2 + 1 \text{ mole of Cl}_2 = 2$ moles of gas
  • Product side: $2 \text{ moles of HCl} = 2$ moles of gas
  • Since the number of moles of gas is equal on both sides, an increase in pressure will have no effect on the position of the equilibrium.

Therefore, an increase in pressure will produce more of the product in reaction B.

The final answer is $\boxed{\text{B) } \text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}}$.