The formula for quantity of thermal energy gained or lost , $$Q$$ , measured in J $$Q=$$

$$Q=mc\Delta t$$ $$\left(J=\frac{g\cdot J\cdot\degree C}{g\cdot\degree C}\right)$$

The formula for molar mass , $$MM$$ , measured in g/mol $$MM=$$

$$MM=\frac{m}{n}$$ $$\left(\frac{g}{mol}=\frac{g}{mol}\right)$$

The formula for molar concentration , $$C$$ , measured in mol/L $$C=$$

$$C=\frac{n}{V}$$ $$\left(\frac{mol}{L}=\frac{mol}{L}\right)$$

The formula for molar enthalpy change , $$\Delta H_n$$ , measured in kJ/mol $$\Delta H_n=$$

$$\Delta H_n=\frac{\Delta H}{n}$$ $$\left(\frac{kJ}{mol}=\frac{kJ}{mol}\right)$$

The formula relating quantity of thermal energy gained/lost in a calorimeter , $$Q$$ , with enthalpy change of a chemical reaction , $$\Delta H$$ , measured in kJ $$Q=$$

$$Q=-\Delta H$$ $$\left(kJ=kJ\right)$$

Combustion is... (endothermic or exothermic)

Exothermic. $$C_xH_yO_z\left(s,l,g\right)+O_2\left(g\right)\rightarrow$$ $$CO_2\left(g\right)+H_2O\left(g\right)+energy$$ Gaseous water ( not liquid) is always a product of combustion.

Endothermic reactions ________ energy. (release or absorb)

Endothermic reactions absorb energy.

Exothermic reactions ________ energy. (release or absorb)

Exothermic reactions release energy.

Three ways to communicate a reaction is endothermic is with... sign of $$\Delta H$$ ? energy as a term ? potential energy diagram ?

Endothermic Reactions: $$\Delta H$$ is positive , $$\Delta H>0$$ Energy is written as a reactant potential energy diagram goes from "low to high"

Three ways to communicate a reaction is exothermic is with... sign of $$\Delta H$$ ? energy as a term ? potential energy diagram ?

Endothermic Reactions: $$\Delta H$$ is negative , $$\Delta H Energy is written as a product potential energy diagram goes from "high to low"

Enthalpy change, $$\Delta H$$ , is always calculated by taking the potential energy of the _______ minus the potential energy of the ______.

Products minus Reactants. $$\Delta H=E_{prods}-E_{reacts}$$

Activation Energy, $$E_A$$ , is always calculated by taking the potential energy of the _______ minus the potential energy of the ______.

Activated Complex minus Reactants. $$\Delta H=E_{act.comp.}-E_{reacts}$$

The standard molar enthalpies of formation in the data booklet are for the __________ of one mole of the compound from its elements (as they exist in nature). (type of reaction)

Formation. For example, $$\Delta_fH_n\degree_{AgCl\left(s\right)}=-127\ \frac{kJ}{mol}$$ , is the enthalpy change for the reaction below, as written and as balanced: $$Ag\left(s\right)+\frac{1}{2}Cl_2\left(g\right)\rightarrow AgCl\left(s\right)\ \ \ \ \Delta H=-127\ kJ$$

$$\Delta_fH_n\degree_{AgCl\left(s\right)}=-127\ \frac{kJ}{mol}$$ This is the standard molar enthalpy of ________ for this compound. (type of reaction)

Formation: $$Ag\left(s\right)+\frac{1}{2}Cl_2\left(g\right)\rightarrow AgCl\left(s\right)+127\ kJ$$

$$\Delta_fH_n\degree_{CH_4\left(g\right)}=-75\ \frac{kJ}{mol}$$ This is the standard molar enthalpy of ________ for this compound. (type of reaction)

Formation: $$C\left(s\right)+2\ H_2\left(g\right)\rightarrow CH_4\left(g\right)+75\ kJ$$

$$\Delta_fH_n\degree_{C_2H_4\left(g\right)}=+52\ \frac{kJ}{mol}$$ This is the standard molar enthalpy of ________ for this compound. (type of reaction)

Formation: $$2\ C\left(s\right)+2\ H_2\left(g\right)+52\ kJ\rightarrow C_2H_4\left(g\right)$$

$$\Delta_cH_n\degree_{CH_4\left(g\right)}=-891\ \frac{kJ}{mol}$$ This is the standard molar enthalpy of ________ for this compound. (type of reaction)

Combustion: $$CH_{4\left(g\right)}+2\ O_2\left(g\right)\rightarrow$$ $$CO_2\left(g\right)+2\ H_2O\left(g\right)+891\ kJ$$

$$\Delta_cH_n\degree_{C_2H_4\left(g\right)}=-1411\ \frac{kJ}{mol}$$ This is the standard molar enthalpy of ________ for this compound. (type of reaction)

Combustion: $$C_2H_{4\left(g\right)}+3\ O_2\left(g\right)\rightarrow$$ $$2\ CO_2\left(g\right)+2\ H_2O\left(g\right)+1411\ kJ$$

$$2\ Mg\left(s\right)+O_2\left(g\right)\rightarrow2\ MgO\left(s\right)\ \ \ \ \ \Delta H=-1200kJ$$ What is the molar enthalpy of reaction for Magnesium oxide in this reaction?

$$\Delta_rH_n\ _{MgO\left(s\right)}=-600\ \frac{kJ}{mol}$$ $$\left(\Delta H_n=\frac{\Delta H}{n}=\frac{-1200\ kJ}{2\ mol}\right)$$

$$2\ Mg\left(s\right)+O_2\left(g\right)\rightarrow2\ MgO\left(s\right)\ \ \ \ \ \Delta H=-1200kJ$$ What is the molar enthalpy of reaction for oxygen in this reaction?

$$\Delta_rH_n\ _{O_2\left(g\right)}=-1200\ \frac{kJ}{mol}$$ $$\left(\Delta H_n=\frac{\Delta H}{n}=\frac{-1200\ kJ}{1\ mol}\right)$$

$$2\ Mg\left(s\right)+O_2\left(g\right)\rightarrow2\ MgO\left(s\right)\ \ \ \ \ \Delta H=-1200kJ$$ How much energy would be released if the reaction used 2 moles of oxygen gas?

$$\Delta H=-2400\ kJ$$ $$\left(\Delta_rH_{n\ O_2\left(g\right)}=\frac{-1200\ kJ}{1\ mol}=-1200\ \frac{kJ}{mol}\right)$$ $$\left(\Delta H=\Delta H_n\cdot n=-1200\ \frac{kJ}{mol}\cdot2\ mol\right)$$