Chapter 16
If you need 3.01 × 1023 molecules of sucrose, how many liters of a 4.00 molar solution would you need?
0.125 L
Which of the following solutions is the most concentrated??
0.5 liter of water with 50 grams of sugar
How many moles of sugar, C12H22O11, are there in 200. grams?
0.585 moles
A sample of water that is 99.9999 percent pure contains 0.0001 percent impurities. Consider from Chapter 1 that a glass of water contains on the order of a trillion trillion (1 × 1024) molecules. If 0.0001 percent of these molecules were the molecules of some impurity, about how many impurity molecules would this be?
1,000,000,000,000,000,000 (one million trillion: 1 × 10^18)
What is the molarity of 0.5 liters of a solution with five moles of sucrose in it?
10 molar
If you need 10 moles of sucrose, how many liters of a 4.0 molar solution would you need?
2.5 L
How many grams of sugar (sucrose) are there in 5 liters of sugar water that has a concentration of 0.5 grams per liter of solution?
2.5 g
A solid has a solubility at room temperature of 78 grams per liter. If 1.0 L of a hot solution containing 100. g of solute is cooled to room temperature, how much solid is formed?
22 g
How many molecules of sucrose are in a 0.5 moles of sucrose?
3.01 × 1023 molecules of sucrose
What is the sum of the atomic masses of all the atoms in sucrose, C12H22O11?
342 amu
If the solubility of a compound is 72 grams per liter, how many grams of the compound will dissolve in 0.50 liters?
36 g
What is the molarity when water is added to 2 moles of sodium chloride to make 0.5 liter of solution?
4 M
How many grams of sodium chloride are needed to make 15 L of a solution that has a concentration of 3.0 g per liter of solution?
45 g
How many moles of water are there in 100. grams of water?
5.55 moles
How many molecules of sucrose are in 0.5 L of a 2 molar solution of sucrose?
6.02 × 1023 molecules of sucrose
Mixtures can be separated into their components by taking advantage of differences in the chemical properties of the components. Why might this separation method be less convenient than taking advantage of differences in the physical properties of the components?
A chemical property involves a chemical change so that you no longer have what you had.
Classify the following as a homogeneous mixture, heterogeneous mixture, element, or compound: table salt.
A compound
What is the difference between a compound and a mixture?
A mixture can be physically separated into its components; a compound cannot be physically separated into its components.
Which of the following material phases cannot form a solution?
All of the above can form solutions
How does a suspension differ from a solution?
Although a solution and suspension are both homogeneous mixtures, only the components of a suspension will separate by spinning the mixture in a centrifuge.
How is the solubility of a gas affected by temperature?
As temperature goes down, the solubility goes up.
At 10°C, which is more concentrated-a saturated solution of sodium nitrate, NaNO3, or a saturated solution of sodium chloride? (See figure shown above )
At 10°C a saturated solution of sodium nitrate, NaNO3, is more concentrated than a saturated solution of sodium chloride, NaCl.
Account for the observation that ethyl alcohol, C2H5OH, dissolves readily in water but dimethyl ether, CH3OCH3, which has the same number and kinds of atoms, does not.
Because dimethyl ether lacks an -OH group, it is significantly less polar than is ethyl alcohol and is not readily soluble in water.
How is the solubility of a solid affected by temperature?
Both A and B As temp goes up, the solubility goes up As temp goes down, the solubility goes down
Why does oxygen have such a low solubility in water?
Both A and B are true.
Why does oxygen have such a low solubility in water??
Both A and B are true.
Someone argues that he or she doesn't drink tap water because it contains thousands of molecules of some impurity in each glass. How would you respond in defense of the water's purity, if it indeed does contain thousands of molecules of some impurity per glass?
Compared to the billions and billions of water molecules, a thousand molecules of something else is practically nothing.
What statement best describes a mole?
It is a very large number chemists use to count atoms or molecules.
Which of the following describes the term concentration?
It is the amount of solute in a given amount of solution.
Which solute graphed above has a solubility in water that does not markedly increase with increasing temperature?
NaCl
Based on atomic size, which would you expect to be more soluble in water: helium, He, or nitrogen, N2?
Nitrogen atoms are bigger and so nitrogen molecules should be more soluble in water due to greater dipole-induced dipole attractions.
Why are noble gases infinitely soluble in noble gases?
Noble gases can be mixed homogeneously in any proportion.
Suggest why sodium chloride, NaCl, is insoluble in gasoline. Consider the electrical attractions.
Salt is composed of ions that are too attracted to themselves. Gasoline is non-polar so salt and gasoline will not interact very well.
If you were to increase the pressure of a gas above a liquid (such as by pressing a piston above a liquid) what happens?
The gas is forced into solution and the solubility increases.
Many solvents expand to occupy greater volumes with increasing temperature. What happens to the concentration of a solution made with such a solvent as its temperature is increased?
Since concentration depends on how much mass is dissolved in a given volume, as the volume increases, the concentration decreases.
Deuterium oxide, D2O, and water, H2O, have the same chemical structure and differ only in that D2O possesses the deuterium isotope of hydrogen, whereas water possesses the protium isotope. Deuterium oxide, also known as "heavy water," is 11 percent heavier than water. Might you expect its boiling temperature also to be about 11 percent greater? Why or why not?
Since they have the same chemical structures, there is a similar molecular attraction between the molecules, so their boiling temperatures are similar.
How are intermolecular forces and solubility related?
Solubility depends on the solvent's ability to overcome the intermolecular forces in a solid.
Why can't the elements of a compound be separated from one another by physical means?
Their atoms are too tightly bound to one another.
Fish don't live very long in water that has just been boiled and brought back to room temperature. Suggest why.
The boiling process removes the air that was dissolved in the water. Upon cooling the water is void of its usual air content, hence, the fish drown.
What is the difference between a compound and a mixture??
The components of a mixture are not chemically bonded together
If nitrogen, N2, were pumped into your lungs at high pressure, what would happen to its solubility in your blood stream?
The greater the pressure, the greater the solubility.
The air that a scuba diver breathes is pressurized to counteract the pressure exerted by the surrounding water. Under these conditions, excessive amounts of nitrogen dissolves in bodily fluids, such as blood. If the diver ascends to the surface too rapidly, the excessive nitrogen bubbles out of the bodily fluids-much like carbon dioxide bubbles out of a soda immediately after its has been opened. This results in a painful and potentially lethal medical condition known as the bends. Why does breathing a mixture of helium and oxygen rather than air help divers to avoid getting the bends?
The helium is less soluble in the bodily fluids and so less dissolves for a given pressure. Upon decompression, there is less helium to "bubble out" and cause potential harm.
What can be said about drinking water that is 99.9999 percent free of some poison, such as a pesticide?
The ratio of water molecules to pesticide molecules in the glass is so great that drinking the water is not problematic.
Would you expect to find more dissolved oxygen in polar or tropical ocean waters? Why?
There would be more dissolved oxygen in the polar oceans because the solubility of oxygen in water decreases with increasing temperature.
When you set a pot of tap water on the stove to boil, you'll often see bubbles start to form well before boiling temperature is ever reached. Explain this observation.
These initial bubbles are the gases that were dissolved in the water coming out of solution. The solubility of gases in water decreases with increasing temperature.
Which of the following solutions is the most dilute??
They all have the same concentration. (if the number of grams of sugar is 10 times as much as the number of liters)
What do chicken noodle soup and garden soil have in common?
They are both example of heterogeneous mixtures
A combination of two or more substances in which they no longer retain their chemical properties is called a(n) ________.
a compound
The following image represents which kind of matter??
a compound (When the 2 shapes are attached)
Classify the following as a homogeneous mixture, heterogeneous mixture, element, or compound: planet Earth.
a heterogeneous mixture
How would you classify the following material? a cappuccino (with foam)
a heterogeneous mixture
Classify the following as a homogeneous mixture, heterogeneous mixture, element, or compound: blood.
a homogeneous mixture
Classify the following as a homogeneous mixture, heterogeneous mixture, element, or compound: steel.
a homogeneous mixture
The following image represents which kind of matter?
a mixture (When 2 different kinds of shaped)
How would you classify the following material? coffee (black)
a solution
How would you classify the following material? coffee (with milk)
a suspension
How would you classify the following material? milk
a suspension
Which of the following is a mixture?
air
Which of the following statements describes a saturated solution?
all of the above
Which has the most atoms?
all of the above have the same number of atoms
Which of the following is a pure substance?
baking soda
Many dry cereals are fortified with iron, which is added to the cereal in the form of small iron particles. How might these particles be separated from the cereal?
collect the iron filings with a magnet
Classify the following as element, compound, or mixture, and justify your classifications: table salt, stainless steel, table sugar, aluminum, ice.
compound; mixture; compound element; compound
Half-frozen fruit punch is always sweeter than the same fruit punch completely melted because
crystallization is a purifying process.
How would you classify the following material? swimming pool water
homogeneous mixture
If you filter sea water to remove all of the particles you would be left with a clear ________.
homogeneous mixture called a solution
When blue food coloring is stirred into water, the result is a ________.
homogeneous mixture called a solution
A sample of steel is composed of 5 percent carbon and 95 percent iron. Which is the solvent?
iron
In a solution of 77 percent nitrogen and 23 percent oxygen, which is the solvent?
nitrogen
Which of the following best describes a two-molar sucrose solution?
one liter of solution that contains 2 moles of sucrose
Which of the following solutions is the most dilute?
one liter of water with 1 gram of sugar
Which of the following solutions is the most concentrated?
one liter of water with 10 grams of sugar
Which of the following would be considered a heterogeneous mixture?
salad dressing
In a solution made from one teaspoon of sugar and one liter of water, which is the solute?
sugar
What property primarily determines the effect of temperature on the solubility of gas molecules?
the kinetic energy of the gas
What is molarity?
the number of moles of solute per liter of solution
Which of the following would be considered a homogeneous mixture?
wine
