Calorimetry and Thermodynamics Review

These flashcards cover key concepts related to calorimetry and thermodynamics for exam review.

Calorimetry

The experimental technique for measuring heat flow for physical or chemical processes.

Calorimetry Equation

q = mcΔT, where q = heat (J), m = mass (g), c = specific heat capacity (J/g·°C), ΔT = temperature change (°C).

Coffee‑cup Calorimeter

An open calorimeter used at constant pressure to measure heat flow.

Bomb Calorimeter

A sealed calorimeter used at constant volume to measure heat flow.

Calorimeter Constant

C_cal; used to account for the calorimeter itself when calculating heat.

Hess’s Law

The total enthalpy change for a reaction is the same regardless of the path taken.

Enthalpy (H)

The sum of internal energy plus pressure-volume work; H = E + PV.

Sign of q for Endothermic Process

Positive (q > 0); indicates heat flows into the system.

First Law of Thermodynamics

ΔE = q + w, where ΔE is the change in internal energy, q is heat added, and w is work done.

Sign Convention for Work

Work (w) is negative if the system expands (ΔV > 0).

qp = ΔH

At constant pressure, the heat flow equals the enthalpy change.

qv = ΔE

At constant volume, the heat flow equals the change in internal energy.

Standard Enthalpy of Formation (ΔHf°)

Enthalpy change when 1 mol of a compound forms from its elements in standard states.

Calculating ΔHrxn°

ΔH_rxn° = Σn ΔHf°(products) - Σm ΔHf°(reactants).

Sign of q for Exothermic Process

Negative (q < 0); indicates heat flows out of the system.

Heat Capacities Relation

C = mc, where C is heat capacity (J/°C) and c is specific heat capacity per unit mass.

Expressing Δ(PV) for Ideal Gas

Δ(PV) = Δ(nRT) = R T Δn if temperature is constant.

Relation between ΔE and ΔH

ΔH = ΔE when there is no gas change (Δngas = 0).

Correcting for Calorimeter Heat Loss/Gain

In a multi-component system: qreaction + qwater + q_cal = 0.

To solve for q_reaction

Use measured ΔT and known mass (m), specific heat (c), and calorimeter constant (C_cal).