General Chemistry - MCAT Chemical and Physical Foundations of Biological Systems

This is a Le Chatlier shift problem. When the equilibrium of a chemical reaction is disturbed, the reaction shifts to the side to minimize the change. Here, increasing H2CO3 would shift the reaction to the right to minimize the addition of the acid. Shifting the reaction to the right would thus increase the concentration of HCO3-.

Remember that Le Chatlier’s principle says that pure liquids and solids do not change the equilibrium of the reaction. Regardless of where in the reaction the pure liquid or solid is present, no equilibrium shift would occur.

This is a Le Chatlier shift problem. When the equilibrium of a chemical reaction is disturbed, the reaction shifts to the side to minimize the change. With pressure, the reaction is shifted to the side with fewer moles of gas. In the carbonic anhydrase reaction, the only gas present would be CO2, a reactant. Decreasing pressure would thus shift the reaction toward the products (right).

This is an undercover Le Chatlier shift problem. The question tells us that vomiting causes us to lose gastric acid. In the equation that we can see above, losing H+ (in HCl) would pull the reaction to the right, increasing the concentration of HCO3-. Increasing the concentration of the base HCO3- increases the pH, leading the blood to become more basic.

This is an undercover Le Chatlier shift problem. If we hyperventilate, we expel more CO2, thus pulling the reaction to the left and decreasing the concentration of H2CO3. As the concentration of the acid decreases, the blood becomes more basic, leading to respiratory alkalosis.

Reducing the volume of the container increases pressure. This results in a higher frequency of gas particle collisions, thereby increasing the rate of the reaction.

Since decreasing the volume of the container has the effect of increasing pressure, equilibrium is shifted to the right. An increase in pressure has the result of favoring the side of the reaction with fewer moles of gas. (According to the balanced equation, there are 4 moles on the reactant side as opposed to 2 moles on the product side).

Good insulators are usually non-metals, in which the electrons are not able to freely move. Insulators, unlike conductors, do not carry current. This is because charges cannot move freely in an insulating material, making this choice the correct answer.

Sound would travel slowest through an insulating material, as there is less ability to compress and propagate the sound wave. Copper is an example of a good conductor, and is a poor insulator.

Halogens are in the group next to the noble gasses. They have seven valence electrons, and therefore have a high electronegativity. The addition of only a single electron (production of an anion) generates a full valence octet.

Their diameters vary within the group. The diameter can be very small, like fluorine, or large, like iodine. They do not conduct electricity well, as they are non-metals.

Transition elements have multiple oxidation states because of the d-orbitals they possess. This allows them to lose or gain electrons in a variety of ways, often leading to the standard characteristics of metals, such as electrical conductivity. Lanthanides and actinides are less commonly tested, but also have the ability to form multiple oxidation states due to their large and variable orbitals. Ytterbium is one of the lanthanides, and has Yb(II) and Yb(III) oxidation states.

The correct answer is cobalt, since it is the only metal among the answer choices. Metals have all the properties described (malleability, ductility, and conductivity). Sulfur, boron, and silicon do not exhibit these properties to the same extent.

The halogens are the second to last column in the periodic table, meaning that they have an affinity for a single additional electron. Halogens would be most likely to react with alkali metals, which contain only one loosely bound electron in the valence shell. Alkali metals have very low ionization energy, readily losing an electron, while halogens have very high electronegativity, readily gaining an electron. This interaction allows the alkali metals to form ionic bonds with the halogens.

Sodium iodide is given by the formula NaI, and has a molecular weight of 150g/mol. Molarity is found by dividing the moles of solute by liters of solvent.

We find the moles of sodium iodide by using the mass (300g) and molecular weight.

We know our volume is 1L, so now we can solve for the molarity.

Solutions can occur in all three phases of matter. They can also occur between two compounds in a single phase. For example, brass is a solution of two metals: zinc and copper.

The properties described fit well with the noble gases. Alkali and alkaline earth elements are solid at room temperature, meaning that they have a high boiling point. Halogens can be gaseous at room temperature, but are very reactive. Noble gases have low boiling points and rarely act in spontaneous reactions. Their properties are due to their full valence shell, which is the source of their stability. Changes to their electron configuration (such as removing an electron) require large amounts of energy.

Alkali metals are much less dense than other metals due to their large radii, which results from having a single loosely bound valence electron. Some of the alkali metals have such low densities that they can float on water.

Atomic radius can be determined using the periodic trends. Atomic radius increases to the left of a period and down a group of the periodic table. Electronegativity, in contrast, increases to the right of a period and up a group of the periodic table. Relating the two, we can see that the greater the atomic radius, the weaker its electronegativity because the electrons are farther away from the nucleus and are unable to feel the attractive force of the protons in the nucleus.

Remember that electronegativity increases as you approach the top right corner of the periodic table. Since oxygen is the farthest right and the highest up on the perioidic table out of these choices, we conclude that it has the highest electronegativity.

The mass number is the total number of nucleons (protons and neutrons) in an atom's nucleus. An atom that undergoes alpha decay will lose a helium nucleus. This decreases its mass number by four. All other forms of radioactive decay listed alter the atomic number of the atom, but not the mass number.

Beta emission involves the conversion of a neutron to a proton and an electron, but only expels the electron.

Electron capture involves the conversion of a proton and an electron into a neutron.

Positron emission involves the conversion of a proton to a neutron and a "positron," or positively charged electron.