Chemistry 1311 - Exam 4

Gaseous chlorine is held in two separate containers at identical temperature and pressure. The volume of container 1 is 1.30 L, and it contains 6.70 mol of the gas. The volume of container 2 is 2.33 L. How many moles of the gas are in container 2?

12.0 mol

A sample of helium gas occupies 14.7 L at 23C and 0.956 atm. What volume will it occupy at 40C and 1.20?

12.4 L

The mass of 1.12 liters of gas Y at STP is founded to be 6.23g. The molar mass of gas Y is

125 g/mol (mass/volume)(STP 22.44)

You are holding two balloons, an orange balloon and a blue balloon. The orange balloon is filled with neon (Ne) gas and the blue balloon is filled with argon (Ar)gas. The orange balloon has twice the volume of the blue balloon. Which of the following best represents the mass ratio of Ne:Ar in the balloons?

1:1

You have two samples of the same gas in the same size container, with the same pressure. The gas in the first container has a Kelvin temperature four times that of the gas in the other container. The ratio of the number of moles of gas in the first container compared to that in the second is

1:4

A balloon has a volume of 2.32 liters at 24.0C. The balloon is heated to 48.0C. Calculate the new volume of the balloon.

2.51 L

A 3.60-L sample of carbon monoxide is collected at 55C and 0.869 atm. What volume will the gas occupy at 1.05 atm and 25C?

2.71L

A gas sample is held at a constant pressure. The gas occupies 3.62 L of volume when the temperature is 21.6C. Determine the temperature at which the volume of the gas is 3.42 L.

278 K

A metal crystallizes with a face-centered cubic lattice. The edge of the unit cell is 395 pm. The diameter of the metal atom is:

279 pm

A metal crystallizes in a body-centered unit cell with an edge length of 2.00*10^2 pm. Assume the atoms in the cell touch along the cube diagonal. The percentage of empty volume in the unit cell will be:

32.0%

The number of Pb atoms per unit cell.

4 (FCC-4)

A sample of oxygen gas has a volume of 1.72L at 27C and 800.0 torr. How many oxygen molecules does it contain?

4.43*10^22

Silver chloride crystallizes with the sodium chloride (rock salt) structure. The length of a unit cell edge is 555 pm. What is the density of AgCl?

5.57 g/cm

Consider a sample of gas in a container on a comfortable spring day. The Celsius temperature suddenly doubles, and you transfer the gas to a container with twice the volume of the first container. If the original pressure was 12 atm, what is a good estimate for the new pressure?

6.4 atm

Chromium metal crystallizes as a body-centered cubic lattice. If the atomic radius of Cr is 1.25 angstroms, what is the density of Cr metal in g/cm?

7.18

In any cubic lattice an atom lying at the corner of a unit cell is shared equally by how many unit cells?

8

You are given a small bar of an unknown metal, M. You find the density of the metal to be 10.5 g/cm. An X-ray diffraction experiment measures the edge of the unit cell as 409 pm. Assuming that the metal crystallizes in a face-centered cubic lattice, what is M most likely to be?

Ag (108g/mol)

Which substance can be described as cations bonded together by mobile electrons?

Ag(s) (Cations bounded- metallic bonding- silver is a metal).

Which contains the largest number of molecules?

All are the same.

When 0.72g of liquid is vaporized at 110C and 0.967 atm, the gas occupies a volume of 0.559 L. The empirical formula of the gas is CH2. What is the molecular formula of the gas?

C3H6

Which of the following would have a higher rate of effusion than C2H2?

CH4

Which of the species below would you expect to show the least hydrogen bonding?

CH4 (non-polar)

In which of the following groups of substances would dispersion forces be the only significant factors in determining boiling points?

I, III, V I. Cl2 III. Ne V. CCl4

Which of the following statements is (are) false?

II II. A body-centered cubic unit cell has four atoms per unit cell. (Has 2)

The bonds between hydrogen and oxygen within a water molecule can be characterized as _________.

Intramolecular forces

Which best explains the following trend? element b.p. (K) He 4 Ne 25 Ar 95 Kr 125 Xe 170

London dispersion forces

Which of the following statements about liquid is true?

London dispersion forces arise from a distortion of the electron clouds within a molecule or atom.

Order the intermolecular forces (dipole-dipole, London dispersion, ionic, and hydrogen-bonding) from weakest to strongest.

London dispersion, dipole-dipole, hydrogen-bonding, and ionic.

The molecules in a sample of solid SO2 are attracted to each other by a combination of

London forces and dipole-dipole interactions

Which of the following should have the lowest boiling point?

N2

Which substances involves no bonding forces except London dispersion forces?

N2(S) London

Which of the following compounds has the lowest viscosity?

N2(g)

Which of the following is the correct order of boiling points for KNO3, CH3OH, C2H6, Ne?

Ne<C2H6<CH3OH<KNO3

Which of the compounds below is not an example of a molecular solid?

SiO2(s)

The freezing point of helium is 270C. The freezing point of xenon is - 112C. Both of these are in the noble gas family. Which of the following statements is supported by these data?

The London dispersion forces between the helium molecules are less than the London dispersion forces between the xenon molecules.

When a non-polar liquid displays a convex meniscus, which of the following explains this behavior?

The cohesive forces are stronger than the adhesive forces to the glass.

You have a certain mass of helium gas (He) in a rigid container. You add same mass of neon gas (Ne) to this container, Which of the following best describes what happen? Assume the temperature is constant.

The pressure in the container increases but does not double.

Dalton's law of partial pressure states that:

The total pressure of a mixture of gases is the sum of the partial pressure of all of the gaseous compounds.

What is responsible for capillary action, a property of liquids?

Two of these

When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction?

a hydrogen from one molecule and an oxygen from the other molecule

For which gas are the collisions elastic?

all gases the same

For which gas do the molecules have the smallest average kinetic energy?

all gases the same

Which of the following would you expect to have the highest boiling point?

i2

The SI unit of pressure is the

pascal

A gas sample is heated from -20.0C to 57.0C and the volume is increased from 2.00L to 4.50L. If the initial pressure is 0.140 atm, what is the final pressure?

0.0811 atm

A glass column is filled with mercury and inverted in a pool of mercury. The mercury column stabilizes at a height of 729 mm above the pool of mercury. What is the pressure of the atmosphere?

0.959 atm

Consider a sample of helium gas in a container fitted with a pistol, as pictured below. The piston is frictionless, but has a mass of 10.0 kg. How many of the following processes will cause the piston to move away from the base and decrease the pressure of the gas? Assume ideal behavior.

1 I. heating the helium.

The unit cell in this two-dimensional crystal contains ___________Xs and _________________Os.

1,1

The local weather forecast reports that the current barometric pressure is 30.4 inches of mercury. What is the current pressure in atmospheres?

1.02 atm

A sample of N2 gas is contaminated with a gas (A) of unkown molar mass. The partial pressure of each gas is know to be 200. torr at 25C. The gases are allowed to effuse through a pinhole, and it is found that gas A escapes at 4 times the rate of N2. The molar mass of gas A is:

1.75g/mol

Body temperature is about 309 K. On a cold day, what volume of air at 276 K must a person with a lung capacity of 2.2 L breathe in to fill the lungs?

1.97 L

Which of the following would represent the greatest pressure?

11.4 psi

What volume is occupied by 21.0 g of methane (CH4) at 27C and 1.25 atm?

25.8 L

You have 41.6g of O2 gas in a container with twice the volume as one with CO2 gas. The pressure and temperature of both containers are the same. Calculate the mass of carbon dioxide gas you have in the container.

28.6 g

The ratio of the average velocity of particles in the first container compared to that in the second is

2:1

The mass of 1.12 liters of gas Y at STP is found to be 6.23g. The density of gas Y is

5.56 g/L D=M/V

Temperature C

C+273= K

Avogadro's law states that:

Equal amounts of gases occupy the same volume at constant temperature and pressure. (6.022*10^23)

Hydrogen bonding is a type of London dispersion force.

False

In general, the density of a compound as a gas is closer in value to that of the compound as a liquid than the density of the compound as a liquid is in value to that of the compound as a solid.

False

Methane (CH4) exhibits stronger hydrogen bond interactions than ammonia (NH3).

False

In which flask do the molecules have the highest average velocity?

Flask A NH3 gas

In which flask are the molecules least polar and therefore most ideal in behavior?

Flask C N2 gas

Hydrogen bonds account for which of the following observation?

For its molar mass, water has a high boiling point.

Which of the following is NOT a postulate of the kinetic molecular theory?

Gas particles have most of their mass concentrated in the nucleus of the atom.

Which of the following is paired incorrectly?

Gold metal - simple cubic unit cell (Gold is very dense, needing more space than a simple cubic unit cell).

You are holding four identical balloons each containing 10.0 g of a different gas. The balloon containing which gas is the largest balloon.

H2

For which gas do the molecules have the highest average velocity?

He

The elements of group 5A, the nitrogen family, form compounds with hydrogen having the boiling points listed below: SbH3-17C, AsH3-55C, PH3-87C, NH3- 33C The first three compounds illustrate a trend where the boiling point decreases as the mass decreases; however, ammonia (NH3) does not follow the trend because of

Hydrogen bonding

Gases generally have

low density

Charles's law states that:

The volume of a fixed amount of gas is directly proportional to its temperature in Kelvin at constant pressure.

Boyle's law states that:

The volume of a fixed amount of gas is inversely proportional to its pressure at constant temperature.

Which of the following statements about solid Cu (face-centered cubic unit cell) is incorrect?

There are two atoms per unit cell. (Cu-copper is FCC, needs 4 atoms).

Intermolecular forces are weaker than intramolecular bonds.

True

Liquids with larger intermolecular forces tend to have high surface tension.

True

Pressure is

defined as the force per unit area

Cubic closest packing is another name for _____.

face-centered cubic packing