Calorimetry

Open to the air, so the pressure never changes. The heat measured at constant P is the enthalpy change.

Mass (m)100 g

ΔT measured25 °C

T initial22 °C

Moles reacted (n)0.050 mol

Progress0%

q = m · c · ΔT

m=100 g

c=4.184 J/g·K

ΔT=+25 °C

q=100 × 4.184 × (+25)

q absorbed by contents+10460J

q of reaction = ΔH-10460J-10.46 kJ

ΔH per mole-209.20kJ/mol

Constant pressure, so q_P = ΔH_rxn. Heat lost by the reaction is exactly the heat gained by the contents.

T initial22.0 °C

ΔT+25.0 °C

T final47.0 °C

−2055130 °C

ExothermicΔH < 0

ΔT > 0 → the calorimeter warms → q_rxn < 0 → heat left the reaction, so it is exothermic

ΔT < 0 → the calorimeter cools → q_rxn > 0 → heat went into the reaction, so it is endothermic

The calorimeter is the surroundings: q_rxn = −q_cal always