Question

What is the balanced chemical equation for the reaction used to calculate ΔH∘f of CaCO3(s)? If fractional coefficients are required, enter them as a fraction (i.e. 1/3). Indicate the physical states using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively without indicating allotropes. Use (aq) for aqueous solution. Express your answer as a chemical equation. The standard enthalpy of formation (ΔH∘f) is the enthalpy change that occurs when exactly 1 mol of a compound is formed from its constituent elements under standard conditions. The standard conditions are 1 atm pressure, a temperature of 25 ∘C , and all the species present at a concentration of 1 M . A "standard enthalpies of formation table" containing ΔH∘f values might look something like this: Substance ΔH∘f H(g) 218 kJ/mol H2(g) 0 kJ/mol Ca(s) 0 kJ/mol Ca2+(aq) −543 kJ/mol C(g) 71 kJ/mol C(s) 0 kJ/mol N(g) 473 kJ/mol O2(g) 0 kJ/mol O(g) 249 kJ/mol S2(g) 129 kJ/mol