BIOL 151 Quiz 2 Study Guide - Energy, Water, and Thermodynamics

Fill-in-the-blank practice flashcards for BIOL 151 Quiz 2 covering bond strength, enthalpy, entropy, free energy, water solutions, pH, and cellular energetics.

The ranking of bond strength from strongest to weakest is polar covalent > nonpolar covalent > __________.

hydrogen bonds

Phase changes such as liquid turning into gas break __________ bonds rather than covalent bonds.

hydrogen

Enthalpy change is calculated using the formula $\Delta H = (\text{enthalpy of bonds formed}) - (\text{enthalpy of bonds } \mathbf{\_\_\_\_\_\_\_\_\_\_})$.

broken

A chemical bond described as having high enthalpy has high potential energy and is considered a __________ bond.

weak

According to the class electronegativity ranking, the correct order is $\text{O} > \text{N} > \text{C} \cong$ __________.

$$\text{H}$$

Carbon forms the structural skeleton of organic molecules because it has low electronegativity and forms __________ covalent bonds.

$$4$$

When dissolving $\text{NaCl}$ in water, a hydration shell forms where $\delta^-$ oxygens surround $\text{Na}^+$ and $\delta^+$ hydrogens surround __________.

$$\text{Cl}^-$$

Hydrophobic molecules consist primarily of nonpolar $\text{C--C}$ and $\text{C--H}$ bonds, which lack partial charges and are __________ from solution.

excluded

In terms of potential energy (enthalpy), a reaction direction is favored when $\Delta H$ is __________.

negative (or $\Delta H < 0$)

In terms of kinetic energy (entropy), a reaction direction is favored when $\Delta S$ is __________.

positive (or $\Delta S > 0$)

According to the Second Law of Thermodynamics, total entropy in the universe is always __________.

increasing

In glucose oxidation ($\text{C}_6\text{H}_{12}\text{O}_6 + 6\,\text{O}_2 \rightarrow 6\,\text{CO}_2 + 6\,\text{H}_2\text{O}$), $\Delta S > 0$ because $7$ reactant molecules become __________ product molecules.

$$12$$

Dissolving salt in an ice pack is an endothermic process ($\Delta H > 0$) that proceeds spontaneously because $-T\Delta S$ creates an overall negative __________.

$$\Delta G$$

Phosphate bonds in ATP are called high-energy bonds because they are __________ and unstable, not because they store energy like a battery.

weak

In the free energy equation $\Delta G = \Delta H - T\Delta S$, the variable $T$ represents temperature measured in __________.

Kelvin

According to the spontaneity rule, a reaction is exergonic and spontaneous when $\Delta G$ is __________.

negative (or $\Delta G < 0$)

On an energy diagram, the height of the energy hump above reactants that must be overcome to break bonds is called the __________ energy.

activation

Reaction spontaneity ($\Delta G < 0$) indicates favorability, but tells you nothing about reaction __________.

speed

Cells drive endergonic reactions primarily by energy coupling to a strongly exergonic reaction, usually __________ hydrolysis.

ATP

Water autoionizes according to the equilibrium equation $\text{H}_2\text{O} + \text{H}_2\text{O} \rightleftharpoons \text{H}_3\text{O}^+ +$ __________.

$$\text{OH}^-$$

Because the pH scale is logarithmic, a solution at $\text{pH } 5$ is __________ times as acidic as a solution at $\text{pH } 7$.

$$100$$

In a condensation reaction, two monomers are covalently linked together while producing a molecule of __________ as a by-product.

water

In methane combustion ($\text{CH}_4 + 2\,\text{O}_2 \rightarrow \text{CO}_2 + 2\,\text{H}_2\text{O}$), the reactant containing the weakest (highest potential-energy) bonds is __________.

$$\text{CH}_4$$

In eukaryotic cells, the citric acid cycle takes place within the mitochondrial __________.

matrix

According to the chemiosmotic hypothesis, ATP synthase is rotated by an electrochemical gradient known as the __________ force.

proton-motive

Among the elements fluorine, oxygen, hydrogen, and sodium, the element with the highest electronegativity is __________.

fluorine

Freezing water is exothermic ($\Delta H < 0$) and forms an ordered crystal structure, which means that $\Delta S$ for the water itself is __________.

negative (or $\Delta S < 0$)