Enthalpy (ΔH)

Calorimetry the measurement of heat flow in/out of a system performed in a calorimeter the heat released by the system is equal to the heat absorbed by the surroundings enthalpy (ΔH) is the heat content in a system heat (q) = enthalpy change (ΔH)

ΔH = m · C · ΔT same formula as before, just substituting ΔH for q When aqueous solutions of 25 ml of HCl and 25 ml of NaOH are mixed in a calorimeter at 21ºC, the temperature rises to 33ºC. What is the enthalpy change? Water’s specific heat is 4.18 J/(g ·ºC). ΔH = 50g · 4.18 J/(g ·ºC) · 12ºC 2,508 J

Heat in Changes of State whenever a substance undergoes a state change, the temp. remains constant as it gains or loses heat example- an ice cube melting gains heat but does not increase in temp. as it melts

molar heat of fusion ΔH fus the heat absorbed by one mole of a substance as it melts to a liquid molar heat of solidification ΔH solid the heat lost by one mole of a substance as it solidifies molar heat of vaporization ΔH vap the heat necessary to vaporize one mole of a liquid molar heat of condensation ΔH cond the heat lost when one mole of a vapor condenses

How many grams of ice will melt if 3.2 kJ of heat are added? The ΔH fus of ice is 6.01kJ/mol. 3.2 kJ x 1 mol ice x 18.0g ice 6.01 kJ 1 mol ice 9.56 g ice

How much heat is absorbed when 24.8 g of water is converted to steam? The ΔH vap of water is 40.7kJ/mol g H 2 O x 1 molH 2 O x 40.7 kJ 18.0 g H 2 O 1 mol H 2 O 56.1 kJ