Chemistry II

What will happen if one tries to form a solution where the enthalpy of solvation is positive and very large and the entropy of solvation is positive, but small?

A solution will not form. When the enthalpy of solvation is very large and outweighs the positive entropy of solvation, a solution will not form. The spontaneity of dissolution depends on the relative sizes of the change in entropy and the change in enthalpy.

The measure of the bond angle in a water molecule is approximately which of the following?

105∘ Water has a tetrahedral electron pair geometry because oxygen is bonded to two hydrogens, and it has two lone pairs of electrons, giving four electron-dense regions around the central oxygen. This results in an angle of about 105∘ between the two hydrogens. Angles of 120∘ are a trigonal planar bond angle with one molecule in the center, three atoms equally spaced around it, and no lone electron pairs. Angles of 180∘ are a linear bond angle with one molecule in the center, two atoms equally spaced around it, and no lone electron pairs. Angles of 90∘ are the bond angles in an octahedral compound, where eight atoms or groups surround a single central atom.

What is true about the hydration process? Select all that apply: Hydration is a solvation process where the solvent is water. The hydration involves breaking ionic solid and mixing in solvent. The hydration involves separating solvent molecules and mixing with ions in solution. The process is generally exothermic. The process is generally endothermic.

Hydration is a solvation process where the solvent is water. The hydration involves separating solvent molecules and mixing with ions in solution. The process is generally exothermic. The enthalpy change for the separation of solvent and the mixing steps are difficult to determine individually. Collectively the two processes are called solvation. If the solvent is water, then this process is called hydration.

An ionic solid has lattice energy of 6473kJmol and a hydration enthalpy of −6443kJmol. The entropy of solution is 652kJmolK. Which of the following statements is true?

The ionic solid will dissolve because the entropy of solution is large enough to outweigh the effects of the positive enthalpy of solution. The enthalpy of solution is defined as the sum of the lattice enthalpy and the hydration enthalpy. Therefore, the enthalpy of solution equals 30kJmol, which means the dissolution is an endothermic process. The entropy of solution is 652kJmolK. Even though the enthalpy of solution is positive, the entropy of solution is large enough to outweigh the effects of the positive enthalpy.

Two clear liquids are poured into a container and immediately separate into layers. What can we conclude about these liquids? Select the correct answer below: One must be a solution and the other a pure solvent. The liquids must have very different polarities. One of the liquids exhibits hydrogen bonding, while the other has very strong dipole-dipole interactions. Their mixing must be an exothermic process.

The liquids must have very different polarities. Because these two liquids do not form a solution, the attractions among their molecules (their polarities) must be vastly different.

Which of the following is equal to the solubility of a solute in a particular solvent? Select all that apply: The maximum equilibrium concentration of solute that can be achieved. The amount of solvent required to dissolve 1g of solute. The amount of solvent required to dissolve 1mol of solute. The concentration of solute in a saturated solution.

The maximum equilibrium concentration of solute that can be achieved. The concentration of solute in a saturated solution. The solubility of a solute in a particular solvent is the maximum equilibrium concentration that may be achieved under certain conditions. When a solute's concentration is equal to its solubility, the solution is said to be saturated with that solute.

When a solution is saturated and additional solute sits at the bottom of the vessel:

The solute will continue to dissolve and precipitate at precisely the same rate so that the concentration will remain fixed. In such a situation there is a dynamic equilibrium, in which some solute precipitates at the same rate that some crystallized solid dissolves. This is why there appears to be no activity: the concentration remains fixed and the solution remains saturated.

Of the following, which are characteristics of weak electrolytes? (select all that apply) Select all that apply: They produce a low concentration of ions when dissolved in water. They are soluble in water. They exhibit no conductivity. They exhibit low conductivity.

They produce a low concentration of ions when dissolved in water. They are soluble in water. They exhibit low conductivity. Weak electrolytes exhibit low (but still some) conductivity and produce a low concentration of ions when dissolved in water.

An electrolyte will yield ions by undergoing a: Select the correct answer below: physical change chemical change spontaneous change depends on the substance

depends on the substance Some electrolytes are ionic solids that dissociate, which would be a physical change, and some are covalent compounds that participate in a chemical reaction with solvent molecules to generate ions.

In forming a solution, the solute always: Select the correct answer below: dissolves dissociates both dissolves and dissociates none of the above

dissolves Not all solutes will dissociate, but all solutes must dissolve in some solvent in order to form a solution. Only ionic solutes will dissociate into cations and anions.

To conduct electricity, a substance must contain which of the following? Select the correct answer below: ions metallic wires water freely mobile charged particles

freely mobile charged particles For a substance to be able to conduct electricity, there must be a freely mobile charged species of some kind. This could be ions in aqueous solutions, or freely moving electrons within a solid metal wire.

Which component of the heat of solution will always be negative? Select the correct answer below: heat of solute heat of solvent heat of mixing none of the above

heat of mixing Mixing the isolated solute particles and isolated solvent particles will always release energy, as favorable interactions will be made.

Which of the following is not a solution? Select the correct answer below: alloy gaseous mixture mud brine

mud All gases will mix homogenously to form solutions (provided that they do not react). Alloys are homogenous solid mixtures containing one metallic element and one or more additional solid components. Brine is a very concentrated aqueous solution of salt. Mud, on the other hand, is not a solution at all.

Dissolution is a process that can always be classified as: Select the correct answer below: exothermic endothermic unfavorable none of the above, it depends on the solution

none of the above, it depends on the solution Some solutes will release heat when they dissolve, while others will absorb heat, so it will depend on the specific solution.

Which substance, when dissolved in water, will conduct the most electricity? Select the correct answer below: ethanol potassium chloride acetic acid ammonia

potassium chloride KCl is the only strong electrolyte among the options, so it will conduct the most electricity.

In seawater, NaCl is the ____________ and H2O is the _______________.

solute, solvent Salt is present in lesser concentrations making it the solute, while water is present in greater concentrations making it the solvent.

If a supersaturated solution is introduced to a mechanical disturbance or a seed crystal, what will happen? Select the correct answer below: there will be further dissolution some solute will precipitate the solution will heat up depends on the solution

some solute will precipitate A supersaturated solution is a delicate system, any disturbance or introduction of a seed crystal will cause solute to precipitate out of solution and crystallize. FEEDBACK

What is the enthalpy of solution? Select the correct answer below: the change in enthalpy associated with the complete dissolution process the change in enthalpy associated with breaking the bonds in an ionic solid the change in enthalpy associated with molecules of solvent separating during the dissolution process the change in enthalpy associated with the solvation of an aqueous ion

the change in enthalpy associated with the complete dissolution process The total enthalpy change for the complete dissolution process is called the heat (or enthalpy) of solution.

If two liquids are said to be immiscible, they display: Select the correct answer below: high mutual solubility very low mutual solubility zero mutual solubility impossible to measure

very low mutual solubility While immiscible liquids will have very low mutual solubility, they will never have zero solubility, as some molecules will inevitably end up in the other layer in the mixture.

Pentane is a particularly nonpolar liquid. Which of the following is likely to be very miscible with pentane? (select all that apply) Select all that apply: A very polar liquid A liquid that is slightly less polar than pentane A liquid that has precisely the same polarity as pentane None of the above

A liquid that is slightly less polar than pentane A liquid that has precisely the same polarity as pentane In general, nonpolar liquids are miscible with other nonpolar liquids, and will always be miscible with other liquids of the same (or nearly the same) polarity.

Which of the following favor the spontaneous formation of a solution? Select all that apply. Select all that apply: An increase in the disorder of a system An increase in the internal energy of a system A decrease in the internal energy of a system A decrease in the disorder of a system

An increase in the disorder of a system A decrease in the internal energy of a system A decrease in the internal energy of a system favors the spontaneous formation of a solution. The formation of a solution is also favored by an increase in the disorder of a system.

Which of the following are properties of liquid water? Select all that apply: It has a very high boiling point when compared to other compounds of similar molecular weight. It is less dense than water in the solid state. It has a low level of cohesion. It can dissolve polar substances, ionic substances, and even some nonpolar gases.

It has a very high boiling point when compared to other compounds of similar molecular weight. It can dissolve polar substances, ionic substances, and even some nonpolar gases. Water has a very high boiling point when compared to other compounds of similar molecular weight. This is due to the strong hydrogen bonds that must be broken for the liquid to boil. Due to its polarity, water can dissolve polar substances, ionic substances, and even some nonpolar gases. The other two choices are incorrect.

Identify the option below that is characteristic of a solution. Its solvent and solute are always present in a 1:1 ratio. It is heterogeneous. Its components are dispersed on a molecular scale. Its physical state is always the same as that of the solute.

Its components are dispersed on a molecular scale. A solution is homogenous, and its components are dispersed on a molecular scale. The physical state of a solution is generally the same as that of the solvent. Its composition, as well as the concentrations of its components, can be varied continuously within a certain range.

Which of the following is not characteristic of a solution? Select the correct answer below: Its components (solute and solvent) may be in the same state. The solute particles are not visible in a solution. It is always homogenous. Its physical state is generally the same as that of the solute.

Its physical state is generally the same as that of the solute. A solution is defined as a homogenous mixture. The physical state of a solution is generally the same as that of the solvent. Its composition, as well as the concentrations of its components, can be varied continuously within a certain range.

Choose the option below that is characteristic of a solution. The solute can be present in any concentration in a solid-liquid solution. It is sometimes heterogeneous. Its composition and the concentrations of its components is always fixed. Its physical state is generally the same as that of the solvent.

Its physical state is generally the same as that of the solvent. A solution is defined as a homogeneous mixture. The physical state of a solution is generally the same as that of the solvent. Its composition, as well as the concentrations of its components, can be varied continuously within a certain range (at a certain point, a solution may become supersaturated). This means that the solute cannot be present at any concentration in a solid-liquid solution; when there is too much solute, it ceases to be a homogeneous solution.

Which of the following are consequences of water expanding when it freezes? Select all that apply: Living cells have a tendency to burst when they freeze. Hydrogen bonds break when water goes from a liquid to a solid state. Ice forms on the surface of bodies of water and remains there, insulating the water below from the cold. The bond angle in water changes from 105∘ to 120∘

Living cells have a tendency to burst when they freeze. Ice forms on the surface of bodies of water and remains there, insulating the water below from the cold. Water is unusual in that its solid form is less dense than its liquid form. This is why ice forms on or near the surface of bodies of water; it is also why living cells generally do not survive freezing because the water in them can expand and damage the cellular structures.

When a solution forms from some compound, the temperature of the solution quickly drops. Which of the following statements is true? Select all that apply: The dissolution process is endothermic. The dissolution process is exothermic. The entropy of solution is likely highly positive. The entropy of solution is likely highly negative.

The dissolution process is endothermic. The entropy of solution is likely highly positive. The dissolution is endothermic because of the drop in temperature. This means that the enthalpy of solution is positive. Therefore, in order for the dissolution to be spontaneous, the entropy of solution must be highly positive to counter the increase in the enthalpy.

Which of the following is not a solution? Select the correct answer below: air an alloy of zinc and copper a mixture of oil and water potassium permanganate dissolved in water

a mixture of oil and water Oil and water are immiscible liquids, meaning they will not form a homogeneous mixture when added together. Therefore, a mixture of oil and water will not be a solution. Air is a gaseous solution: a homogeneous mixture of nitrogen, oxygen, and several other gases. Many alloys are solid solutions of one metal dissolved in another; for example, US five-cent coins contain nickel dissolved in copper. When a small amount of solid potassium dichromate is added to water, potassium dichromate will dissolve and dissociate to form a solution of potassium ions and dichromate ions.

An alloy is a solution in which: Select the correct answer below: a gas is dissolved in a solid a liquid is dissolved in a solid a solid is dissolved in a solid a solid is dissolved in a liquid

a solid is dissolved in a solid An alloy is a homogeneous mixture of two metals.

The property of water that allows it to travel from roots to leaves in tall trees, often distances of hundreds of feet, is referred to as __________. Select the correct answer below: adhesion cohesion solvation specific heat

adhesion The property of water that allows it to travel from roots to leaves in tall trees, often distances of hundreds of feet, is referred to as adhesion. It is the result of the attraction between molecules of one substance to molecules of another. The ability of a liquid to flow against gravity in narrow spaces is also known as capillary action. Cohesion is the attraction of the particles of the same substance for each other. Solvation refers to the interaction between a solute and solvent when a solution forms. Specific heat refers to the relationship between heat absorbed and temperature gained in a substance.

Which of the following statements describes lattice energy?

all of the above Separating particles of solute involves overcoming the intermolecular interactions that hold the particles together, or the lattice energy. The energy of the solute is also called the lattice energy. The lattice energy is equal to the enthalpy change that occurs when 1mol of ionic solid is converted into gaseous ions.

Solubility is determined by: Select the correct answer below: solute-solute forces solvent-solvent forces solute-solvent forces all of the above

all of the above The relative strengths of all of these attractions will determine the solubility of a particular solute for a particular solvent.

Of the following, which will always result from the spontaneous formation of a solution? Select the correct answer below: a decrease in the internal energy of a system an increase in the entropy of a system and the surroundings an increase in the internal energy of a system a release of heat from the system

an increase in the entropy of a system and the surroundings The spontaneous formation of a solution results in an increase in the entropy of the system and the surroundings. The internal energy of the system can increase or decrease because the formation of a solution can be either endothermic or exothermic.