CaCO3 (s) + 2HCl (g) ↔ CaCl2 (s) + H2O (l) + CO2 (g) ∆H = –90 kJ/mol, chemistry homework help

The reaction below occurs in a closed system. The reactants were mixed and the reaction was allowed to reach equilibrium.
- Is this reaction a single replacement or a double replacement? Explain your answer.
- If more HCl is added to the system, how will the reactions shift to reach equilibrium again?
- If CO₂ is removed from the system, how will the reactions shift to reach equilibrium again?
- If heat is added to the system, how will the reactions shift to reach equilibrium again?
- What is the principle that helps identifies shifts in equilibrium?

CaCO₃ (s) + 2HCl (g) ↔ CaCl₂ (s) + H₂O (l) + CO₂ (g) ∆H = –90 kJ/mol