WARM UP 1.Given the thermochemical equation H 2 + I 2  2 HI, ΔH° rxn = 52 kJ/mol. What is ΔH° for the reaction HI  ½ H 2 + ½ I 2 ? 2.Given that the heat of solution of LiF is +32 kJ/mol and that the lattice energy for LiF is 1006 kJ/mol, calculate the heat of hydration of Li + and F - ions.

Calorimetry Chemistry II

Calorimetry Terms Calorimetry – Measurement of heat changes calorie – Energy (heat) measurement – Amount of heat needed to raise the temperature of 1 g of water by 1°C (4.184 J) Calorie – Food energy – 1000 calories (1 kcal) – kJ

Calorimetry Terms Calorimeter – Closed system to measure heat changes – Uses water to absorb heat q rxn = -(q calorimeter + q water )

Calorimetry Terms Calorimeter – Constant-pressure Simple (styrofoam cups) Commonly used

Calorimetry Terms Calorimeter – Constant-volume (“bomb”) Sealed steel chamber Used for food measurements

Calorimetry Terms Specific heat (s) – Amount of heat required to raise the temperature 1 gram of the substance by 1° C – Unit is J / g · °C Heat capacity (C) – Amount of heat required to raise the temperature of a given quantity of a substance 1° C – Unit is J / °C

Specific Heat (s) Equation q = msΔt – heat = mass x specific heat x temp. change

Heat Capacity (C) Equation q = CΔt – heat = heat capacity x temp. change

Conversion Equation C = ms – Heat capacity = mass x specific heat

WRAP UP Describe how specific heat and heat capacity are related, but not exactly the same.

WARM UP 1.Compare and contrast a bomb calorimeter with a constant pressure calorimeter. 2.Explain how the specific heat/heat capacity of water is related to a food Calorie.

WRAP UP A piece of iron initially at a temperature of 25.2 °C absorbs 16.9 kJ of heat. If its mass is 82.0 g, calculate the final temperature. The specific heat of iron is.444 J/g°C.

WARM UP 1.What is the heat capacity of a block of lead if the temperature of a 425-g block increases 2.31 °C when it absorbs 492 J of heat?