Topic 2: Energy and Chemistry Flashcards

50 practice flashcards covering Energy and Chemistry lecture content, including forms of energy, calorimetry, enthalpy, Hess's Law, thermochemical equations, and battery technologies.

What is the mathematical equation for gravitational potential energy?

$P.E. = mgh$, where $m$ is mass in kilograms, $g$ is acceleration due to gravity ($9.8\,m/s^2$ at Earth's surface), and $h$ is height in meters.

What is the formula for electrostatic potential energy ($E_{el}$) between two charged particles?

$$E_{el} = \frac{k Q_1 Q_2}{d}$$

What is the value of the proportionality constant $k$ in electrostatic potential energy?

$$k = 9 \times 10^9\,N\,m^2/C^2$$

What is the equation for kinetic energy?

$\text{Kinetic energy} = \frac{1}{2} m v^2$, where $m$ is mass in kilograms and $v$ is velocity in meters per second.

What constitutes the internal energy of an object?

The combined kinetic and potential energies of the atoms and molecules that make up the object.

How is chemical energy defined?

Energy stored within the structural units of chemical substances, determined by the type and arrangement of constituent atoms.

What equation relates radiant energy ($E$) to frequency ($\nu$)?

$$E = h \times \nu$$

What is the value of Planck's constant ($h$)?

$$6.63 \times 10^{-34}\,J\,s$$

What is the wave equation relating the speed of light ($c$), wavelength ($\lambda$), and frequency ($\nu$)?

$c = \lambda \times \nu$, where $c = 3.00 \times 10^8\,m/s$.

How is mechanical energy defined?

Energy associated with the movement of macroscopic objects, combining both kinetic and potential energy.

What is thermal energy?

The energy associated with the random motion of atoms and molecules, which can be calculated from temperature measurements.

How is electrical energy calculated from power and time?

$\text{Energy} = \text{Power} \times \text{Time}$, where power is in watts, time is in seconds, energy is in Joules, and $1\,\text{watt-sec} = 1\,\text{Joule}$.

What is nuclear energy?

A form of potential energy associated with the arrangement of protons and neutrons in atomic nuclei, which can be released in nuclear fusion and fission processes.

How is energy broadly defined in thermodynamics?

The capacity to do work or transfer heat.

What is the formula for work ($w$) performed by moving an object?

$w = F \times d$ or $w = m \times a \times d$, where $F$ is force, $d$ is distance, $m$ is mass, and $a$ is acceleration.

In which direction does heat naturally flow between objects?

Heat flows from warmer objects to cooler objects.

What is the most common type of work encountered in chemical processes?

Pressure-volume work ($PV\text{-work}$).

What is the conversion factor between calories ($\text{cal}$) and Joules ($\text{J}$)?

$$1\,\text{cal} = 4.184\,\text{J}$$

What is the difference between the system and surroundings in thermodynamic studies?

The system includes the specific molecules being studied, whereas the surroundings comprise everything else.

Based on standard thermodynamic sign conventions, what do the signs of heat ($q$) and work ($w$) indicate?

Heat added to the system is $+q$, heat lost by the system is $-q$, work done on the system is $+w$, and work done by the system is $-w$.

What is the mathematical expression for the First Law of Thermodynamics for internal energy change ($\Delta E$)?

$$\Delta E = q + w$$

According to the Law of Conservation of Energy, how does $\Delta E_{\text{system}}$ relate to $\Delta E_{\text{surroundings}}$?

$\Delta E_{\text{system}} = -\Delta E_{\text{surroundings}}$, so $\Delta E_{\text{universe}} = \Delta E_{\text{surroundings}} + \Delta E_{\text{system}} = 0$.

What is the typical energy conversion efficiency of an electric heater or hair dryer?

$$\sim 100\%$$

What is the typical energy conversion efficiency of an electric generator?

$$95\%$$

What is specific heat capacity?

A physical property of a material that measures how much heat is required to raise the temperature of one gram of that material by $1\,K$ ($1\,^\circ C$).

What is the formula for heat ($q$) calculated using mass and specific heat capacity?

$$q = m c \Delta T$$

What is molar heat capacity ($C_p$)?

A physical property that describes how much heat is required to raise the temperature of one mole of a substance by $1\,K$ ($1\,^\circ C$) at constant pressure.

What is the formula for heat ($q$) calculated using moles and molar heat capacity?

$$q = n C_p \Delta T$$

What is the specific heat capacity of liquid water ($H_2O(l)$)?

$4.184\,J\,g^{-1}\,K^{-1}$ (or $4.184\,J\,g^{-1}\,^\circ C^{-1}$)

What is the molar heat capacity of liquid water ($H_2O(l)$)?

$$75.3\,J\,mol^{-1}\,K^{-1}$$

If heating a $24.0\,g$ aluminum can raises its temperature by $15.0\,^\circ C$, what is $q$ for the can (given $c_{\text{Al}} = 0.900\,J\,g^{-1}\,^\circ C^{-1}$)?

$$q = 324\,J$$

What is calorimetry?

The technique or measurement used to quantify the amount of heat involved in a chemical or physical process.

What major component parts are present in a steel bomb calorimeter assembly?

An insulated outside chamber, water bath, stirrer, thermometer, ignition wires, sample dish, burning sample, and steel bomb.

What are the two steps in making a calorimetric measurement?

1. Calibration (generating a known heat input to determine the calorimeter constant); 2. The actual measurement (determining heat absorbed or released in a reaction).

How is the heat absorbed by a calorimeter ($q_{\text{calorimeter}}$) calculated?

$$q_{\text{calorimeter}} = C_{\text{calorimeter}} \times \Delta T$$

How does the heat flow of a reaction ($q_{\text{reaction}}$) relate to the heat flow of the calorimeter ($q_{\text{calorimeter}}$)?

$$q_{\text{reaction}} = -q_{\text{calorimeter}}$$

What is the mathematical definition of enthalpy ($H$)?

$H = E + PV$, where $E$ is internal energy, $P$ is pressure, and $V$ is volume.

At constant pressure, what physical quantity is equal to the change in enthalpy ($\Delta H$)?

$\Delta H = q$ (the heat gained or lost by the system at constant pressure).

What are the signs of $\Delta H$ for endothermic and exothermic reactions?

Endothermic process: $\Delta H > 0$ (positive, heat gained). Exothermic process: $\Delta H < 0$ (negative, heat lost).

How is the change in enthalpy ($\Delta H$) calculated during a phase change?

$\Delta H = n \times \Delta H_{\text{phase change}}$, where $n$ is the number of moles.

How are the heat of condensation ($\Delta H_{\text{cond}}$) and heat of vaporization ($\Delta H_{\text{vap}}$) related?

$$\Delta H_{\text{cond}} = -\Delta H_{\text{vap}}$$

What is the standard molar enthalpy of fusion ($\Delta H_{\text{fus}}$) for water at $0\,^\circ C$?

$$6009.5\,J/mol$$

What is a thermochemical equation?

A balanced chemical equation that specifies the physical states of reactants and products and includes the corresponding enthalpy change ($\Delta H$).

What is Hess's Law?

The enthalpy change of an overall process is the sum of the enthalpy changes of its individual steps.

What happens to the sign and magnitude of $\Delta H$ when a chemical equation is reversed?

$\Delta H$ retains the same magnitude but takes the opposite sign.

What is the formula to calculate $\Delta H^\circ$ for a chemical reaction using standard enthalpies of formation ($\Delta H_f^\circ$)?

$$\Delta H^\circ = \sum v_i \Delta H_f^\circ(\text{products}) - \sum v_i \Delta H_f^\circ(\text{reactants})$$

What is energy density?

The amount of energy that can be released or liberated per unit mass (e.g., per gram or per kilogram) of fuel burned.

Which fuel listed in the lecture table has the highest energy density?

Hydrogen, with an energy density of $142.0\,MJ/kg$.

How do primary and rechargeable battery types compare regarding energy density and cost according to tabulated data?

Among primary batteries, Lithium and Zinc-Air have high energy density, whereas Alkaline is medium; among rechargeable batteries, Lithium Ion has high energy density and high cost, while Nickel-Cadmium has low energy density and low cost.

What four positive factors support the widespread use of petroleum as a liquid fuel?

(1) It is a liquid (easy to transport and deliver); (2) It is relatively safe; (3) Combustion products are gases (easy to dispose of); (4) It has a high energy density.