Chapter 8 HW

Classify the following phase changes as processes that require the input of energy, or as processes that have a net output of energy. Drag the appropriate items to their respective bins.

Output of energy: *freezing *condensing *deposition Input of energy: *melting *subliming *vaporizing

Watch the video to determine which of the following relationships are correct according to Boyle's law. Check all that apply.

P & 1/V V & 1/P

Part B A gas, behaving ideally, fills a fixed pressure and temperature container at a volume V1 and number of moles n1. The number of moles of the container is changed to n2. Using Avogadro's, Charles', or Boyle's law, develop an expression that would be used to solve for the new volume V2.

V1/n1=V2/n2

A 14.0 L gas cylinder is filled with 6.40 moles of gas. The tank is stored at 25 ∘C . What is the pressure in the tank? Express your answer to three significant figures and include the appropriate units.

ANSWER for P= 11.2 atm (Formula: P: ? V: 14.0 L n: 6.40 mole R:.0821 l*atm/k*mol T: 25c + 273= 298K P= (6.40mol x 298K x 0.0821 l*atm/k * mol) / 14.0 L= 11.18 ==> 11.2 atm)

High-pressure liquid chromatography (HPLC) is a method used in chemistry and biochemistry to purify chemical substances. The pressures used in this procedure range from around 500 kilopascals (500,000 Pa) to about 60,000 kPa (60,000,000 Pa). It is often convenient to know the pressure in torr. If an HPLC procedure is running at a pressure of 4.14×108 Pa , what is its running pressure in torr? Express the pressure numerically in torr.

ANSWER: 3.10*10^6 atm (use asterisk symbol not x symbol or answer will be wrong in system.) (NOTE: 4.14 x10^8 pa (1.00 atm/ 101,352 Pa( (760 torr/ 1.00 atm)= 3.10x10^6 torr)

Part A Convert 0.600 atm of pressure to its equivalent in millimeters of mercury. Express the pressure numerically in millimeters of mercury.

ANSWER: 456 (NOTE: .600 atm x (760 mmHg/ 1.00 atm) = 456 mmHg )

Part A A cylinder, with a piston pressing down with a constant pressure, is filled with 2.10 moles of a gas (n1), and its volume is 41.0 L (V1). If 0.800 mole of gas leak out, and the pressure and temperature remain the same, what is the final volume of the gas inside the cylinder? Express your answer with the appropriate units.

ANSWER V2: 25.4 L (formula: V1: 41.0 n1: 2.10 mole V2: ? n2: -.800 mole V2= (41.0L x (2.10 mole - .800 mole) / 2.10= 25.380 ==> 25.4 L)

A 14.0 L gas cylinder has been filled with 5.60 moles of gas. You measure the pressure to be 3.00 atm . What is the temperature inside the tank? Express your answer to three significant figures and include the appropriate units.

ANSWER for K= 91.2K (Formula: P: 3.00 atm V: 14.0L n: 5.60 mole R:.0821 l*atm/k*mol T: ??? (Formula: T= (3.00 atm x 14.0L) / (5.60 mole x 0.0821 l*atm/L*mol) = 91.35 ==> 91.2 K)

Part B Consider 4.40 L of a gas at 365 mmHg and 20. ∘C . If the container is compressed to 2.00 L and the temperature is increased to 30. ∘C , what is the new pressure, P2, inside the container? Assume no change in the amount of gas inside the cylinder. Express your answer with the appropriate units.

ANSWER for P2= 830 mmHg (NOTE: formula: P2 = (303K x 365mmHg x 4.40L) / (2.00L x 293K)= 830.406 ==> 830 mmHg)

Crystalline solids are well-ordered arrays of atoms or molecules. Crystalline solids may be atomic solids, molecular solids, or ionic solids. Part A Classify these solids as molecular, ionic, or atomic. Drag each item to the appropriate bin.

Atomic solids: S(s), Cu(s), Ar(s) Molecular solids: CCl4(s), C12H22O11(s) Ionic solids: CuS(s), MgCl2(s), KI(s)

A sealed glass jar has a small amount of water on the bottom. The rest of the volume in the jar is taken up by helium gas at a partial pressure of 526 mmHg, and water vapor. If the total pressure inside the jar is 760. mmHg, what is the temperature of the water? Express your answer to three significant figures and include the appropriate units.

T = 70.0 ∘C

Identify which of the following molecules can exhibit hydrogen bonding as a pure liquid. Check all that apply.

Make sure O, N, or F is attached to H.

Watch the animation and select the interactions that can be explained by hydrogen bonding. Check all that apply.

*HF has a higher boiling point than HCl. *Ice, H2O, has a solid structure with alternating H−O interactions.

In the simulation, set the temperature of the sample gas to 304 K. Click on the "Run" button, and observe how the number of moles of the gas varies with an increase in the volume of the gas. Then, click on the "Reset" button, set the temperature of the sample gas to 504 K, and click on the "Run" button again. Observe the graph produced in the simulation, and select the correct options listed below. Check all that apply.

*The volume of the sample gas increases linearly with the number of moles *The volume of the gas doubles when the number of moles of the gas is doubled at the same temperature

Part B Consider a gas in a sealed, rigid container. Which of the following will increase if more gas is pumped into the container at constant temperature? Check all that apply.

*the number of gas particles *the collision frequency of the gas particles *the pressure of the gas (NOTE: Adding more gas increases the number of gas particles, which increases the collision frequency of the particles, which increases the amount of force applied to a given area of the container wall at any given time, which increases the pressure.)

Part A Consider a gas in a sealed, rigid container. Which of the following will increase if the temperature of the gas is increased? Check all that apply.

*the pressure of the gas *the speed of the gas particles *the kinetic energy of the gas particles *the collision force of the gas particles (NOTE: Increasing temperature increases the kinetic energies of the particles, which increases the speed of the particles, which increases the collision force of the particles, which increases the pressure.)

In the video, you can see that as heat is applied to a solid, it is converted into the liquid phase and then into the gas phase. This process can be studied by plotting the graph of temperature verses the time during which heat is applied to the system. Identify the states of matter and the processes that occur at each of the positions on the graph. Drag the appropriate labels to their respective targets.

1. Heating of the Solid 2. Melting of the Solid 3. Heating of the liquid 4. Boiling of the liquid 5. Heating of the gas (note: Point a is the melting point of the solid. The line ab represents the melting process of the solid, during which the solid and liquid are in equilibrium. Point c is the boiling point of the liquid. The line cd represents the boiling process of the liquid, during which the liquid and gas are in equilibrium.)

Part D If a certain gas occupies a volume of 14 L when the applied pressure is 7.0 atm , find the pressure when the gas occupies a volume of 3.5 L. Express your answer to two significant figures, and include the appropriate units.

28 atm (NOTE: The initial volume ( V1 ) is 14L , and the initial pressure ( P1 ) is 7.0atm ; the final volume ( V2 ) is 3.5L . Using P1V1 = P2 V2 , you get P2=P1V1/V2 =(7.0×14)/3.5 = 28 atm (7.0 atm x 14 L) / 3.5 L = 28 atm)

You are in a mountain range with atmospheric air pressure of 520 mmHg, and you wish to boil some eggs. What is the approximate boiling point of the water at this air pressure? Express your answer as an integer and include the appropriate units.

89 ∘C

Part A A very flexible helium-filled balloon is released from the ground into the air at 20. ∘C. The initial volume of the balloon is 5.00 L, and the pressure is 760. mmHg. The balloon ascends to an altitude of 20 km, where the pressure is 76.0 mmHg and the temperature is −50. ∘C. What is the new volume, V2, of the balloon in liters, assuming it doesn't break or leak? Express your answer with the appropriate units.

ANSWER for V2: 38.1 L (NOTE: formula: V2=(223K x 760 mmHg x 5.00L) / (293K x 76.0 mmHg)= 38.054 ==> 38.1 L )

Part A A balloon is floating around outside your window. The temperature outside is 39 ∘C , and the air pressure is 0.800 atm . Your neighbor, who released the balloon, tells you that he filled it with 3.40 moles of gas. What is the volume of gas inside this balloon? Express your answer to three significant figures and include the appropriate units.

ANSWER for V= 109 L (Formula: P: 0.800 atm V: ? n: .3.40 R: 0821 l*atm/k*mol T: 39c + 273= 312K V= (3.40mole x 312K x .0821 l*atm/k*mol) / .800 atm= 108.8646 ==> 109 L)

Part C A 240. L kiln is used for vitrifying ceramics. It is currently operating at 1065 ∘C , and the pressure is 1.000 atm . How many moles of air molecules are within the confines of the kiln? Express your answer to three significant figures and include the appropriate units.

ANSWER for n= 2.18 mole (Formula: P: 1.000 atm V: 240L n: ??? R:.0821 l*atm/k*mol T: 1065 c + 273= 338K (Formula: n= (1.000 atm x 240L)/ (1338K x 0.0821 l*atm/K*mol) = 2.184801 ==> 2.18 mole)

Part B A sample of gas in a cylinder as in the example in Part A has an initial volume of 44.0 L , and you have determined that it contains 1.80 moles of gas. The next day you notice that some of the gas has leaked out. The pressure and temperature remain the same, but the volume has changed to 11.0 L . How many moles of gas (n2) remain in the cylinder? Express your answer with the appropriate units.

ANSWER n2= 0.450 mole (formula: V1: 44.0L n1: 1.80 mole V2: 11.0L n2: ? n2= (11.0L x 1.80 mole) / 44.0L) = .450 mole)

Part B The pressure in car tires is often measured in pounds per square inch (lb/in.2), with the recommended pressure being in the range of 25 to 45 lb/in.2. Suppose a tire has a pressure of 26.5 lb/in.2 . Convert 26.5 lb/in.2 to its equivalent in atmospheres. Express the pressure numerically in atmospheres.

ANSWER: 1.80 atm (NOTE: 26.16 lb/in^2 x (1.00 atm / 14.7 lb/in^2) = 1.779 ==> 1.80 ) )

Part B - Practice the steps for a one-step problem Once you've identified the initial and final conditions, you're ready to solve for the unknown quantity in your problem. Boyle's Law expresses the pressure-volume relationship as P1V1=P2V2, so you will need to solve this equation for the unknown quantity and then plug in your known values to calculate the unknown. What pressure would it take to compress 300. L of helium gas initially at 1.00 atm into a 2.00 L tank at constant temperature? Express your answer with the appropriate units.

ANSWER: 150 atm (SOLUTION: (1.00 atm x 300 L) / 2.00 L= 150 atm )

Part C - Practice the steps for a multi-step problem Sometimes the problem will give the initial and final states in different units. In this case, you need to identify all of the pressures and all of the volumes by organizing them into a table (step 1 of our problem-solving method). Then, you need to convert all of your pressures to the same units (usually atmospheres works best) and all of your volumes to the same units (usually liters). Then you can set up the problem and solve. A balloon filled with 2.00 L of helium initially at 1.55 atm of pressure rises into the atmosphere. When the surrounding pressure reaches 320. mmHg, the balloon will burst. If 1 atm = 760. mmHg, what volume will the balloon occupy in the instant before it bursts? Express your answer with the appropriate units.

ANSWER: 7.36 L (NOTES: convert mmHg to atm: 320 mmHg x (1 atm / 760 mmHg) = .421 atm (1.55 atm x 2.00 L) / .421 atm = 7.36L )

A volume of 18.0 L contains a mixture of 0.250 mole N2 , 0.250 mole O2 , and an unknown quantity of He. The temperature of the mixture is 0 ∘C , and the total pressure is 1.00 atm . How many grams of helium are present in the gas mixture? Express your answer to three significant figures and include the appropriate units.

ANSWER: mass of He: 1.21 g

Part C At 4.00 L, an expandable vessel contains 0.864 mol of oxygen gas. How many liters of oxygen gas must be added at constant temperature and pressure if you need a total of 2.00 mol of oxygen gas in the vessel? Express the volume to three significant figures, and include the appropriate units.

Answer =5.26 L

A mixture of He, Ar, and Xe has a total pressure of 3.00 atm . The partial pressure of He is 0.250 atm , and the partial pressure of Ar is 0.350 atm . What is the partial pressure of Xe? Express your answer to three significant figures and include the appropriate units.

Answer: 2.40 atm (Formula: Given: pTotal = 3.00 atm p(He) = 0.250 atm p(Ar) = 0.350 atm use: pTotal = p(He) + p(Ar) + p(Xe) 3.00 atm = 0.250 atm + 0.350 atm + p(Xe) p(Xe) = 2.40 atm Answer: 2.40 atm)

Part A - Organize the data Since volume and pressure are inversely related, we can make some assumptions about initial and final states using the data provided. We can also identify initial and final states by finding trigger words in the language of the problem. Look for words like "first," "initially," or "originally" to describe initial states and "result" or "after" for final states. What volume would a sample of helium occupy at 5.0 atm if the helium was initially compressed in a 1.0 L tank at 20. atm at constant temperature? Organize your data into the table to help analyze the problem. Leave blank any boxes for which you do not have information. Drag the appropriate labels to their respective targets.

CORRECT ANSWER: Initial condition Pressure: 20 atm Final Condition Pressure: 5.0 atm Know: P decreases Initial condition Volume: 1.0 L Predict: V increases (NOTE: P1: 20 atm V1: 1 .0 L P2: 5.0 atm V2:?? Solve for V2 than determine if the Volume has increase or decrease for the predict section. (20 atm x 1.0 L) / 5.0 atm = 4L) )

In the video, you can see that when heat is applied to a solid it is converted into the liquid phase and then into the gas phase. This process can be studied by plotting the graph of temperature verses the time during which heat is applied to the system. Using this information, arrange the average kinetic energy of the molecules for the following options in decreasing order. Rank from highest to lowest. To rank items as equivalent, overlap them.

HIGHEST -----> LOWEST (LEFT TO RIGHT): 1. The average kinetic energy of the molecules after point d 2. The average kinetic energy of the molecules from point b to point c 3. The average kinetic energy of the molecules before point a

The hydrides of group 5A are NH3, PH3, AsH3, and SbH3. Arrange them from highest to lowest boiling point. Rank the molecules from highest to lowest boiling point. To rank items as equivalent, overlap them.

HIGHEST ----> TO LOWEST: SbH3, NH3, AsH3, PH3

Part B Arrange the following crystalline solids in order of decreasing melting point. Rank the solids from highest to lowest melting point. To rank items as equivalent, overlap them.

Highest Melting Point --> Lowest Melting Point: KCl(s), CH3OH(s), Ar(s)

Part A A gas, behaving ideally, has a pressure P1 and at a volume V1. The pressure of the gas is changed to P2. Using Avogadro's, Charles', or Boyle's law, develop an expression that would be used to solve for the new volume V2.

P1V1=P2V2

What will happen if you put some 20 ∘C water in a vacuum chamber and reduce the pressure to less than 18 mmHg?

The water will boil. (NOTE: You are more used to boiling water by raising its temperature, which increases the vapor pressure to greater than 760 mmHg. But it is possible to lower the surrounding pressure to achieve the same effect. Recall that, for liquid water, atmospheric pressure is greater than vapor pressure. And for water to transition to the gas phase, vapor pressure must be greater than atmospheric pressure.)

Imagine that the gas shown in the simulation is an ideal gas such as helium. Notice that the final number of moles of gas is 1.00 mol for each experimental run. You can find the final volume of the gas using the y axis of the graph shown. Consider an experimental run at 273 K where the initial number of moles (n1) is actually 1.00 mol, and the final number of moles (n2) is 2.00 mol. Use the simulation to find the volume (V1) of 1.00 mol of helium at 273 K, and calculate the final volume (V2). Express the volume to three significant figures, and include the appropriate units.

V2 = 44.8 L

Part B Standard temperature and pressure (STP) are considered to be 273 K and 1.0 atm. Predict which of the following changes will cause the volume of the balloon to increase or decrease assuming that the temperature and the gas filling the balloon remain unchanged. Drag the appropriate items to their respective bins.

Volume increases: *Balloon filled with helium at STP floats into the atmosphere where the pressure is 0.5 atm. *Balloon filled with helium under water at 1.15 atm is released and floats to the surface, which is at STP. Volume decreases: *Balloon filled with helium at STP is submerged under water where the pressure is 1.25 atm. Volume is unchanged: *Balloon filled with helium at STP floats into air where the pressure equals 1 atm.

Part C A certain gas is present in a 12.0 L cylinder at 2.0 atm pressure. If the pressure is increased to 4.0 atm , the volume of the gas decreases to 6.0 L . Find the two constants ki, the initial value of k, and kf, the final value of k, to verify whether the gas obeys Boyle's law. Express your answers to two significant figures separated by a comma

ki, kf = 24,24