Final answer:
The energy change when 14.2g of chlorine reacts completely with hydrogen is -36.984 kJ.
Step-by-step explanation:
In the given reaction, 2HCl(g) → H₂+Cl₂, the enthalpy change (∆H) is -184 kJ.
To calculate the energy change when 14.2g of chlorine reacts completely with hydrogen, we need to convert the mass of chlorine to moles. The molar mass of chlorine (Cl₂) is approximately 70.906 g/mol, so 14.2 g is equal to 14.2/70.906 = 0.201 mol of chlorine.
Since the reaction produces 1 mole of hydrogen chloride (HCl) for every 1 mole of chlorine, the energy change for 0.201 mol of chlorine reacting completely with hydrogen would be 0.201 x -184 kJ = -36.984 kJ.