Correct answer: Molten Cryolite conducts electricity because it furnishes charged particles.

Why?:

Cryolite is an ionic compound. When in solution, it ionizes to produce charged particles. These are the sodium cations, aluminum cations, and the fluoride anions. To conduct electricity a substance must have charged particles that are mobile. Molten cryolite has three different ions that can move through the liquid, allowing the flow of charge from one end of a sample of molten cryolite to the other.

Answering this question:

Always remember that electricity is the flow of electrons. Electrons are charged particles. This also means that the ions can conduct electricity if they are moving from one place to another to facilitate the flow of charges.

Therefore, molten cryolite conducts electricity because it furnishes ions in the solution.

Correct answer: 3.9 mL

Why?:

Density is the ratio of the mass of a substance to its volume. The volume can just be derived if the density and the mass of the substance are known. A given substance has a unique density and this can serve as a qualitative basis for the identity of a substance.

Correct answer: Density

Why?:

Density is a physical property of any material. It is defined as the mass of a substance per unit volume. Each substance has a unique density. This means a substance can be identified through its density. Moreover, density is an intensive property. This means that it is independent of the size of the substance. No matter how big or how small a gold sample will be, the density will still be the same.

Archimedes measured the mass of the crown. He also determined the volume using water-displacement method. He compared the data obtained to the masses and volumes of gold, tin, and copper. If the mass and the volume of the crown was the same with that of gold, then he could have concluded that the crown is made purely of gold. However, it was found out that the data gathered using the crown were not the same with that of gold. So he concluded that the crown is not made purely of gold.

Answering this question:

Notice that the only physical property Archimedes obtained were the mass and the volume. With the mentioning of the water displaced by the crown, we would have the idea that it was volume that was being measured. It is through water-displacement method. Since density is defined as the mass of a substance per unit volume, then Archimedes used the density of the materials to verify the purity of the gold crown.

So the correct answer is density.

Correct Answer: 47.9 L

Why?:

The International Union of Pure and Applied Chemists (IUPAC) defines standard temperature and pressure (STP) as 273.15 Kelvin and 0.986 atmosphere (atm), respectively. The relationship among temperature, volume, and pressure of gases is defined by the Combined Gas Law.

Correct answer: 2.5 g

Why?:

A saturated solution is a solution that contains the maximum amount of solute that a given amount of solvent can dissolve. This is the limit of the solubility of a substance in a given solvent.

The hydrocarbon 1-pentanol is a primary alcohol with five carbons in its carbon chain. The above graph identifies it as having 2.5 g solubility in 110 grams of water. This means that 110.0 grams of water can only dissolve 2.5 g of 1-pentanol.

Answering this question:

Determine first the number of carbon atoms 1-pentanol contains. Since it has the prefix "penta" which means five, then 1-pentanol contains five carbon atoms. Locate in the x-axis the number 5. Draw an imaginary line going upwards from x=5 until it intersects with a point on the curve. From the point on the curve, draw an imaginary line going to the left and determine the y-value. The y-value is the mass in grams of 1-pentanol that can be dissolved in 110 grams of water.

So the correct answer is 2.5 g.

Correct answer: Solubility of a primary alcohol in water is inversely proportional to the total number of carbon atoms in the primary alcohol.

Why?:

An alcohol has polar and nonpolar portions. The presence of the O-H group in a primary alcohol gives the alcohol a polar character. The hydrocarbon chain however is nonpolar. As the number of carbon atoms increase in a primary alcohol, its nonpolar character increases. This makes the alcohol less soluble in the polar water.

Answering this question:

Locate at least two different points in the curve. Obtain the solubility values for each of the points. Do the same with the total number of carbon atoms. Just simply compare each pair of values. Establish what happens to solubility when the total number of carbons increase. Does it also increase? If so, then the relationship is directly proportional. If it is otherwise, then the relationship is inversely proportional.

In this case here, solubility decreases as the total number of carbon atoms increases.

So the relationship is inversely proportional.

Correct answer: Boiling point of the solution is higher than the boiling point of pure ethanol.

Why?:

This is known as boiling point elevation. It is a colligative property of solutions. The dissolved substance in ethanol reduces the vapor pressure of ethanol by effectively reducing the surface area of the solution. The molecules of the solute on the surface take up space that would have been occupied by an ethanol molecule. With less surface area exposed to ethanol, evaporation becomes more difficult. A higher temperature will be needed to convert liquid ethanol molecules to gaseous ethanol molecules. A higher temperature is needed to reach boiling.

Answering this question:

This requires careful analysis. Think of boiling as the escape of molecules from the liquid phase to the gas phase. This could only happen if the molecule is not tightly bound to the liquid phase. An ethanol molecule is held by other ethanol molecules. A solute will just enhance this force that holds an ethanol molecule. In effect, the ethanol molecule cannot easily get out of the liquid phase. A higher temperature will give the ethanol molecule a greater energy. With this, the ethanol molecule will be able to get loose and escape into the gas phase. Thus, a higher temperature is needed to facilitate the escape of the ethanol molecule to the gas phase.

So boiling temperature of a solution of ethanol with a nonvolatile solute will be higher than that of pure ethanol.

Correct answer: (2) 249 K

Why?:

Temperature is the hotness or coldness of a body. It is also a measure of the total potential and kinetic energy in a system.

The SI unit for temperature measurements is the Kelvin scale. Although most countries widely use the Celsius and Kelvin scale, there are still those that use the Fahrenheit scale.

The Kelvin scale is a Celsius scale shifted downwards such that 0K=-273.15˚C. Many use the value -273 instead of the -273.15. To convert Celsius to Kelvin and vice versa, the following formula is be used.

K = ˚C + 273.15

˚C = K - 273.15

Answering this question:

It is necessary to know the formula in converting Celsius to Kelvin. Simply add the value 273.15 to the given ˚C measurement to get the Kelvin equivalent.

K = ˚C + 273.15

K = -24 + 273.15

K = 249.15 K

Among the choices, the nearest to 249.15 K is 249 K of choice (2). The value of  249 K simply means that the Kelvin value used in the computation is 273 and not 273.15.

So the best answer is (2).

Correct answer: (3) Fe

Why?:

The standard temperature and pressure (STP) are 25˚C and 1 atm, respectively. At these conditions, F₂ and Br₂ are gases. Fe is a solid metal, and Hg is a liquid metal. If at standard conditions a substance is a gas, then its melting point is way below the standard temperature. If a substance is liquid at these conditions, then its melting point is also below the standard temperature. If a substance is a solid, then its melting point is way above the standard temperature.

Answering this question:

The periodic table is a picture that paints a thousand words. Even without any knowledge on the elements exact melting points, this question can still be answered correctly with the help of the periodic table. Fluorine and bromine are located on the right side of the zigzag line on the periodic table. This means that they are gases. And so at 25˚C, they do not need to melt because they are already gases. Mercury and iron are both on the left side. They are metals. But knowing iron as a very famous metal used in many industrial structures, and mercury as the only liquid metal, it would be rightful to conclude that iron is the answer in this question. Mercury is already a liquid at 25˚C and it does not need to melt. It is already melted.

So this leaves us with (3) as the correct answer.

Correct answer: (2) moles of solute per liter of solution.

Why?:

Molarity is the number of moles of solute per liter of solution.

Answering this question:

Molarity is one of the ways of expressing concentrations of solutions. Concentrations speak about how much solute is dissolved in a given solvent. It should state both the amount of solute and the given amount of solvent. Knowing this, (3) and (4) can then be eliminated. Choice (3) does not talk about both the solute and the solvent. It just talks about the solution as a whole. Choice (4) only talks about the solvent and there is nothing that gives us knowledge on how much solute is involved.

Molarity has the unit moles per liter. Knowing this, it will give us a straightforward idea that molarity is the number of moles of solute per liter solution. It is also because choice (1) talks about the kilogram of solvent and not referring to liter.

So this leaves us with (2) as the correct answer.