A solution is a homogeneous mixture whose composition is uniform throughout.
Correct Answer
True
True. A solution is a homogeneous mixture of two or more substances, and its solute particles are dispersed on a molecular scale so the composition is the same everywhere. The solute particles do not settle out.
Category: Dissolution Process
Question 2
In a solution, the solute is the component present in the greatest concentration.
Correct Answer
False
False. The solvent is the component present in the greatest concentration; the solute or solutes are present in lesser amounts. Water is the most common solvent, but gases and solids can also serve as solvents.
Category: Dissolution Process
Question 3
Air is a gaseous solution of nitrogen, oxygen and other gases.
Correct Answer
True
True. Air is a homogeneous mixture of gases, so it is a solution, with nitrogen as the major component acting as the solvent. Solutions can exist in the gas, liquid or solid state.
Category: Dissolution Process
Question 4
A solute dissolves spontaneously only when the dissolution process releases heat.
Correct Answer
False
False. Endothermic dissolution can also be spontaneous, because the increase in the dispersal of matter (entropy) can drive solution formation. Ammonium nitrate dissolving in water, used in instant cold packs, is a spontaneous endothermic example.
Category: Dissolution Process
Question 5
Ethanol is a nonelectrolyte because it dissolves in water without forming ions.
Correct Answer
True
True. Ethanol molecules stay intact and uncharged when they dissolve, so the solution contains no ions to carry current. In a conductivity test, an ethanol solution does not light the bulb.
Category: Electrolytes
Question 6
Acetic acid is a strong electrolyte because it ionizes completely in water.
Correct Answer
False
False. Acetic acid is a weak acid that ionizes only to a small extent, so it is a weak electrolyte. Its solution conducts electricity poorly, giving only a dim bulb in a conductivity test.
Category: Electrolytes
Question 7
An ionic compound that is only slightly soluble in water is still classified as a strong electrolyte, because the portion that dissolves dissociates essentially completely.
Correct Answer
True
True. Electrolyte strength depends on the degree of dissociation of what dissolves, not on how much dissolves. Ionic compounds dissociate nearly completely, so even sparingly soluble ones are strong electrolytes.
Category: Electrolytes
Question 8
According to Henry's law, doubling the partial pressure of a gas above a liquid at constant temperature doubles the gas's solubility.
Correct Answer
True
True. Henry's law states that the solubility of a gas is directly proportional to its partial pressure, C = kP, where k depends on the gas, the solvent and the temperature. Doubling P therefore doubles C.
Category: Solubility
Question 9
The solubility of most gases in water increases as the temperature rises.
Correct Answer
False
False. Gas solubility in water generally decreases as temperature rises. This is why warm water holds less dissolved oxygen and why a warm carbonated drink loses its fizz faster.
Category: Solubility
Question 10
Opening a bottle of soda raises the pressure of CO2 above the liquid, which makes dissolved gas bubble out.
Correct Answer
False
False. Opening the bottle lowers the pressure of CO2 above the liquid. By Henry's law the gas solubility falls with that pressure, so the excess dissolved CO2 comes out as bubbles.
Category: Solubility
Question 11
For many ionic and molecular solids, heating the water allows more of the solid to dissolve.
Correct Answer
True
True. For many solids, solubility in water rises with temperature, although there are exceptions such as cerium sulfate. This trend lets a hot saturated solution be cooled carefully to form a supersaturated one.
Category: Solubility
Question 12
Nonpolar benzene mixes readily with water because like dissolves like.
Correct Answer
False
False. Like dissolves like means polar liquids mix with polar liquids and nonpolar with nonpolar. Benzene is nonpolar and water is polar, so they are immiscible and form separate layers.
Category: Solubility
Question 13
The mole fractions of all the components of a solution add up to 1.
Correct Answer
True
True. Each mole fraction is the moles of one component divided by the total moles of all components, so the fractions sum to exactly 1. Mole fraction has no units.
Category: Concentration Units
Question 14
Dissolving a nonvolatile solute in a solvent raises the vapor pressure of the solvent.
Correct Answer
False
False. A nonvolatile solute lowers the vapor pressure of the solvent. By Raoult's law the solution's vapor pressure equals the solvent's mole fraction times the pure solvent's vapor pressure, and that mole fraction is less than 1.
Category: Colligative Properties
Question 15
Spreading salt on icy roads works because dissolved ions lower the freezing point of water.
Correct Answer
True
True. Dissolved solute particles depress the freezing point of water, so the brine stays liquid below 0 °C. Salts that give more ions per formula unit, such as calcium chloride, depress it more for the same molality.
Category: Colligative Properties
Question 16
In the equation for osmotic pressure, the temperature is expressed in degrees Celsius.
Correct Answer
False
False. Osmotic pressure is calculated from MRT with the temperature in kelvin, matching the units of R, 0.08206 L·atm/(mol·K). Using a Celsius value gives a wrong result.
Category: Colligative Properties
Question 17
Colloidal particles are small enough that they do not settle out of the dispersion on standing.
Correct Answer
True
True. Colloidal particles are larger than most simple molecules but still small enough to stay dispersed rather than settle. Many are aggregates of hundreds or thousands of molecules.
Category: Colloids
Question 18
A gel is a colloid in which a gas is dispersed throughout a liquid.
Correct Answer
False
False. A gel is a liquid dispersed throughout a solid that forms a three-dimensional network, as in gelatin desserts and jellies. Gas dispersed in a liquid is a foam.
Category: Colloids
Question 19
Soap molecules have a nonpolar hydrocarbon tail and an ionic end, which lets them suspend oily dirt in water.
Correct Answer
True
True. The nonpolar tail dissolves in grease while the ionic carboxylate end interacts with water, so soap molecules surround oily dirt and keep it suspended as a colloid that rinses away.
Category: Colloids
Question 20
A Cottrell precipitator removes colloidal particles from smoke by passing it through a semipermeable membrane.
Correct Answer
False
False. A Cottrell precipitator is electrostatic: charged colloidal particles in smoke are attracted to highly charged electrodes, where they are neutralized and collected as dust. It does not use a membrane.
Category: Colloids