AP Biology Quiz 1 Ch. 2,3

Water's high specific heat is mainly a consequence of the absorption and release of heat when hydrogen bonds break and form. This is because water molecules are able to form hydrogen bonds with each other, which are relatively strong and require a significant amount of energy to break. When heat is added to water, these hydrogen bonds absorb the energy, causing the water molecules to move faster and increase in temperature. Conversely, when heat is removed from water, the hydrogen bonds release the energy, helping to stabilize the temperature. This property allows water to resist temperature changes and maintain a stable environment, making it an excellent regulator of temperature in both living organisms and the environment.

Isotopes are atoms of the same element that have different numbers of neutrons. In this case, Atom 1 and Atom 2 are both hydrogen atoms (1H), but Atom 1 has 1 neutron while Atom 2 has 3 neutrons. Therefore, they are isotopes of each other.

Since oxygen has an atomic number of 8, it means that it has 8 protons in its nucleus. The number of protons in an atom is equal to the number of electrons, so oxygen also has 8 electrons. The number of neutrons in an atom can vary, but it is not determined by the atomic number. Therefore, the correct answer is that oxygen has 8 protons and 8 electrons, making option A and B correct.

NH4 forms an ionic bond with Cl to make ammonium chloride salt. Ionic bonds occur when there is a transfer of electrons between atoms, resulting in the formation of oppositely charged ions. In this case, NH4 donates one electron to Cl, forming NH4+ and Cl- ions. These ions are attracted to each other due to their opposite charges, creating an ionic bond.

Atoms whose valence shells are filled with electrons are stable and unreactive. This is because the valence shell is the outermost shell of an atom and when it is completely filled, the atom has achieved a stable electron configuration. As a result, these atoms do not readily participate in chemical reactions. Additionally, atoms with filled valence shells exhibit similar chemical behaviors because they have similar electron configurations, leading to similar chemical properties.

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Both polar covalent bonds and hydrogen bonds must be broken for water to vaporize. Polar covalent bonds are the bonds between the oxygen and hydrogen atoms within a water molecule, while hydrogen bonds are the attractions between the positive hydrogen atom of one water molecule and the negative oxygen atom of another water molecule. Breaking these bonds allows the water molecules to escape from the liquid phase and become a gas during vaporization.

Buffers are substances that help maintain the pH of a solution by resisting changes in acidity or alkalinity. In basic solutions, the pH is higher, meaning it is more alkaline. To resist a shift towards acidity, a buffer should release H+ ions, which are acidic. Therefore, the correct answer is releasing H+ in basic solutions. This helps to counteract the increase in pH and maintain a stable pH level.

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When an ice cube cools a drink 1 degree C, a kilocalorie of heat is transferred to the ice. This is because heat always flows from a higher temperature object to a lower temperature object, so the heat from the drink is transferred to the colder ice cube in order to equalize the temperatures. This transfer of heat causes the ice cube to melt and absorb the energy, resulting in a decrease in temperature of the drink.

Chemical equilibrium is a state in a chemical reaction where the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products over time. This means that while the reactions are still occurring, the concentrations of reactants and products remain constant. Therefore, the correct answer is "Reactions continue with no effect on the concentrations of reactants and products."

When the pH of a solution increases from 8 to 9, it indicates that the concentration of H+ ions has increased. A change of one unit in pH represents a tenfold change in the concentration of H+ ions. Therefore, the concentration of H+ ions is 10 times greater than it was at pH 8.

The given molecule, H-O-C-C=O, is most likely to exist because it follows the valences of carbon, oxygen, hydrogen, and nitrogen. Carbon has a valence of 4, oxygen has a valence of 2, hydrogen has a valence of 1, and nitrogen has a valence of 3. In the given molecule, carbon has four bonds, oxygen has two bonds, hydrogen has one bond, and nitrogen has three bonds. Therefore, this molecule is the most likely to exist based on the valences of the atoms involved.

The given statement is correct because NH3 (ammonia) is a weak base, as it only partially dissociates in water to form hydroxide ions. HCl (hydrochloric acid) is a strong acid, as it completely dissociates in water to form hydrogen ions. Therefore, NH3 can accept fewer hydrogen ions compared to HCl, making NH3 a weak base and HCl a strong acid.

When the pH of the blood drops, it means that the concentration of hydrogen ions (H+) has increased. In order to restore pH stability, the bicarbonate ion (HCO3-) acts as a base and removes the excess hydrogen ions by combining with them to form carbonic acid (H2CO3). This reaction helps to maintain the balance between carbonic acid and bicarbonate ions, thus stabilizing the pH of the blood.

NaCl is not a strong base because it does not ionize completely in solution. It is actually a salt that is formed from the reaction between a strong acid (HCl) and a strong base (NaOH). When NaCl is dissolved in water, it dissociates into Na+ and Cl- ions, but it does not contribute to the concentration of hydroxide ions (OH-) in the solution, which is characteristic of a strong base.

An element with atomic number 16 is sulfur. Sulfur has 6 valence electrons, and it needs 2 more electrons to achieve a stable octet. Therefore, it can form 2 covalent bonds with hydrogen to fulfill its electron requirement. However, the question asks for the maximum number of covalent bonds, so the correct answer is 1.

Water molecules can form a maximum of four hydrogen bonds. Each water molecule has two hydrogen atoms and two lone pairs of electrons. These hydrogen atoms can form hydrogen bonds with the lone pairs of electrons on neighboring water molecules. Since each water molecule has two lone pairs of electrons, it can form a maximum of four hydrogen bonds with four neighboring water molecules. Therefore, the correct answer is four.