Chemistry Exam Review

Select all of the choices that correspond to exothermic reactions or processes. ΔH > 0 q < 0 ΔH < 0 q > 0

q < 0 ΔH < 0

Which of the following quantities are state functions? Select all that apply. A) volume B) heat C) work D) internal energy E) temperature

volume, internal energy and temperature.

Is work done on the system or by the system in the following scenarios? In each case, the system is underlined. A) A person rows a boat across a lake. B) A person pedals a bicycle down the street.

work done by the system work done on the system

For which reactions or processes would you expect the change in entropy (∆S) to be less than zero? Select all that apply. -2 O2(g) + 2 SO(g) → 2 SO3(g) -I2(s) → I2(g) -Ca3(PO4)2(s) → 3 Ca2+(aq) + 2 PO43-(aq) -Condensation -H2O(s) → H2O(l)

- 2 O2(g) + 2 SO(g) → 2 SO3(g) - Condensation

Which of the following statement(s) about ideal gases is/are true? Select all that apply. -Energy is not lost when molecules of ideal gas collide. - Increasing pressure causes gases to behave more ideally because it makes the volume of gas particles appreciable with respect to the volume of the container. - Molecules of F2 gas and Cl2 gas have the same kinetic energy at 875 K. - Kinetic molecular theory adequately explains why increasing the number of moles of gas in a sample increases pressure. - Particles of gas are more attracted to one another at 1000 K than at 300 K because the particles at 1000 K have greater kinetic energy.

- Energy is not lost when molecules of ideal gas collide. -Molecules of F2 gas and Cl2 gas have the same kinetic energy at 875 K. -Kinetic molecular theory adequately explains why increasing the number of moles of gas in a sample increases pressure.

Use the information below to determine the standard enthalpy of reaction for the reaction: B2H6(g) + 6 Cl2(g) → 2 BCl3(g) + 6 HCl(g). Enter your response in kilojoules to the nearest 1 kJ and with appropriate sign. BCl3(g) + 3 H2O(l) → H3BO3(g) + 3 HCl(g) ∆H° = -112.5 kJ ½ H2(g) + ½ Cl2(g) → HCl(g) ∆H° = -92.5 kJ B2H6(g) + 6 H2O(l) → 2 H3BO3(g) + 6 H2(g) ∆H° = -493.5 kJ

-1,378.5

A 20.0 mL sample of 0.50 M NaOH and a 20.0 mL sample of 0.50 M H2SO4 are combined in a coffee-cup calorimeter. The temperature of the combined solutions increases from 20.4 ºC to a maximum of 26.7 ºC. Assuming that the calorimeter loses no heat to the surroundings, what is ∆H for the reaction in kilojoules per mole? You may assume that the density of the solution is 1.0 g/mL and the specific heat capacity is that of water. Enter your response to the nearest 1 kJ/mol with appropriate sign.

-105.4

The overall reaction in a commercial heat pack can be represented as: 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s), ∆Hº = -1652 kJ What is the change in enthalpy when 2.00 g of Fe(s) is reacted with excess oxygen? Enter your response in kilojoules to the nearest 0.1 kJ and with appropriate sign.

-14.9

Calculate ΔHº for the reaction 4 SO2(g) + 2 O2(g) → 4 SO3(g) given the following information. Enter your response in kilojoules to the nearest 1 kJ with appropriate sign. 2 SO3(g) → 2 SO2(g) + O2(g) ΔHº = 200 kJ

-400

A 5.00 g sample of CaCl2 is dissolved in 125.0 mL of water in a coffee-cup calorimeter. From the beginning to the end of the dissolution process, the temperature increases from 22.5 ºC to 27.8 ºC. Which statements are true? Select all that apply. -The change in enthalpy for the dissolution is endothermic. -The change in enthalpy for the dissolution is negative. -The dissolution is exothermic. -The dissolution is endothermic.

-The change in enthalpy for the dissolution is negative. -The dissolution is exothermic.

chapter 18: Which of the following statements best describes a spontaneous chemical reaction? -The reaction occurs without external intervention in a continuous manner. -The reaction is exothermic. -The reaction occurs only with continuous intervention. -The reaction occurs rapidly.

-The reaction occurs without external intervention in a continuous manner.

The second law of thermodynamics states that ∆S univ > 0 for all spontaneous processes. Which combination(s) of entropy changes in the system and surroundings can be associated with a spontaneous process? Select all that apply. - ΔSsystem > 0, ΔSsurroundings > 0 -ΔSsystem < 0, ΔSsurroundings < 0 -ΔSsystem > 0, ΔSsurroundings< 0 -ΔSsystem < 0, ΔSsurroundings > 0

-Δ Ssystem > 0, ΔSsurroundings > 0 -ΔSsystem > 0, ΔSsurroundings< 0 - ΔSsystem < 0, ΔSsurroundings > 0

How many moles of a gas are present in a sample that occupies 425 mL at 1.00 atm and 298 K? Enter your answer without units to the nearest 0.001 mol.

0.017

What is the specific heat capacity of a substance if it takes 1155 J of heat to raise the temperature of 100. g of substance from 25.0 ºC to 55.0 ºC? Enter your response in Joules per degree Celsius per gram to the nearest 0.001 J ºC-1 g-1.

0.385

By what ratio does the volume of a gas increase when its temperature is increased from 9.00 ºC to 27.0 ºC at constant pressure?

1.06

What is the new volume (in L) of a 2.00 L sample of gas when the pressure increases from 1.85 atm to 3.75 atm and the temperature increases from 325 K to 475 K? Assume that the moles of gas remain constant. Enter your response without units to the nearest 0.01 L

1.44

Calculate the entropy in Joules per Kelvin (J/K) of a 50.0 g sample of carbon monoxide (CO) assuming that each CO molecule can be oriented exactly 2 ways. Enter your answer without units to the nearest 0.1 J/K.

10.3

The change in internal energy for a given system is -325 J. The system loses 155 J of energy as heat at the same time that it expands from an initial volume of 15.0 L at 1.00 atm of pressure. What is the final volume of the system in liters? Enter your response without units to the nearest 0.1 L.

16.7

What is the melting point of a compound A? The standard enthalpy and entropy of fusion for A are listed below. Enter your response in Kelvin to the nearest 1 K. A(s) → A(l) ∆H° = 8.1 kJ mol-1 ∆S° = 42.4 J mol-1 K-1

191

For which process would you expect ∆Sº to be most positive? - NH3(g) + HCl(g) → NH4Cl(g) - 2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g) - H2O(l) → H2O(s) - N2O4(g) → 2 NO2(g) - O2(g) + 2 H2(g) → 2 H2O(g)

2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g)

A 25.0 g block of metal initially at 95.0 ºC is placed in a calorimeter containing 121 g of water initially at 27.2 ºC. The specific heat capacity of the metal is 0.49 J ºC-1 g-1. The heat capacity of water is 4.184 J ºC-1 g-1. Assuming that no heat is lost to the calorimeter or the surroundings, what his the final temperature of the water and metal? Enter your response in degrees Celsius to the nearest 0.1 ºC.

28.8

A given system gains 200 J of heat while 150 J of work are done on it. What is the change in internal energy (in J) for this system? Enter your response without units to the nearest 1 J. If the answer is positive, then you do not need to enter a + sign. If it is negative, then you must enter the - sign.

350

The total pressure of a mixture of O2(g), Ne(g), and Ar(g) is 13.4 atm. What is the partial pressure of Ne(g) if PO2 = 6.5 atm and PAr = 2.7 atm? Enter your response to the nearest 0.1 atm and without units.

4.2

Convert 0.400 L⋅atm to Joules. Enter your response without units to the nearest 0.1 J.

40.5

What is the change in enthalpy (in kJ) associated with the decomposition of 4.00 moles of SO3? Consider the data below. Enter your response without units to the nearest 1 kJ. 2 SO3(g) → 2 SO2(g) + O2(g) ΔHº = 200 kJ

400

How much energy (in Joules) is required to raise the temperature of 10.0 g of H2O(l) by 10.0 ºC? The specific heat capacity for H2O(l) is 4.184 J/g⋅⋅ºC. Enter your response without units to the nearest 0.1 J.

418.4

Container A contains a gas under 3.24 atm of pressure. Container B contains a gas under 2.82 atm of pressure. Container C contains a gas under 1.21 atm of pressure. If all of these gases are put into Container D, then what is the pressure in Container D? Enter your response in atmospheres (atm) to the nearest 0.01 atm. Container A = 1.23 dm3 Container B = 0.93 dm3 Container C = 1.42 dm3 Container D = 1.51 dm3 1 dm3 = 1000 mL

5.51

N2O5 is an unstable gas that decomposes according to the following balanced equation. 2 N2O5(g) → 4 NO2(g) + O2(g) A sample of N2O5 is placed into a 5.00 L container at 25.00 °C. The initial pressure inside the container is 304 torr. What is the partial pressure of NO2 after the sample of N2O5 decomposed if the temperature after reaction is 37.2 °C? You may assume 100% decomposition and no change in volume during the reaction. Enter your response in torr and without units, to the nearest 1 torr.

633

chapter 7: Identify the correct relationship between each pair of variables for gases. A) pressure and volume B) volume and temperature C) volume and moles D) pressure and temperature 1) inversely proportional 2) directly proportional

A) 1 B) 2 C) 2 D) 2

Which substance would you expect to have the greatest standard molar entropy? -CH3OH(g) -CH3CH2OH(g) -CH3OH(l) -H2O(l) -CH3CH2OH(l)

CH3CH2OH(g)

potential energy

Energy that is stored and held in readiness

Which sample would you expect to have the greatest entropy? -H2O(g) at 500 K -H2O(l) -H2O(s) -H2O(g) at 300 K

H2O(g) at 500 K

Which sample of gas has the greatest root-mean-square speed? - Ne at 345 K -Ar at 293 K -O2 at 320 K -F2 at 305 K -He at 375 K

He at 375 K

mechanical energy

Kinetic or potential energy associated with the motion or position of an object

Which of the following substances has a standard enthalpy of formation equal to zero? -NO2(g) -N2(g) -H2O(s) -HCl(aq) -CH3OH(aq)

N2(g)

A 5.43 g sample of an elemental diatomic gas occupies 4.38 L at 25 ºC and 0.950 atm. What is the identity of the gas? - F2 - Br2 - Cl2 - N2 - O2

O2

Which sample of gas has the greatest average kinetic energy? - Ar at 298 K - He at 330 K - F2 at 275 K - Ne at 312 K - O2 at 340 K

O2 at 340 K

At constant pressure, the reaction below is endothermic. N2O4(g) → 2 NO2(g) The reaction (as written) is... -Spontaneous at all temperatures -Spontaneous at no temperature -Spontaneous only above T=ΔHo/ΔSo -Spontaneous only below T=ΔHo/ΔSo

Spontaneous only above T=ΔHo/ΔSo

Which statement is true concerning ΔG^orxn andΔGrxn? - There is only one value of ΔGrxnfor a given reaction at a given T and there are many values of ΔG^orxn because there are infinite variations of standard conditions and only one set of non-standard conditions. - There is only one value of ΔG^orxn for a given reaction at a given T and there are many values of ΔGrxn because there is only one set of standard conditions and infinite variations of non-standard conditions. - There is only one value of ΔGrxn for a given reaction at a given T and there are many values of ΔG^orxn because there is only one set of standard conditions and infinite variations of non-standard conditions.

There is only one value of ΔG^orxn for a given reaction at a given T and there are many values of ΔGrxn because there is only one set of standard conditions and infinite variations of non-standard conditions.

Which gas do you expect to effuse most slowly if all samples are at the same temperature and pressure? - Kr - Ar - He - Ne - Xe

Xe

Which statement regarding the freezing of water is true? - Water freezes spontaneously only below T=ΔH/ΔS because both ΔH and ΔS are positive for this phase change. - Water freezes spontaneously only above T=ΔH/ΔS because both ΔH and ΔS are positive for this phase change. - Water freezes spontaneously only below T=ΔH/ΔS because both ΔH and ΔS are negative for this phase change. - Water freezes spontaneously only above T=ΔH/ΔS because both ΔH and ΔS are negative for this phase change.

Water freezes spontaneously only below T=ΔH/ΔST because both ΔH and ΔS are negative for this phase change.

chapter 8:The frequency of light of a given wavelength can be calculated using which expression? Frequency is equal to... c/λ λν λ/ν cλ

c/λ

kinetic energy

energy of motion; The kinetic energy, KE, of an object is mathematically related to its mass, m, and velocity, v, as shown in the following equation.

Which of the following quantities are incorporated in the definition of Gibbs free energy? Select all that apply. -entropy -temperature -internal energy -enthalpy -work

entropy, temperature, enthalpy

Under which conditions do you expect a sample of gas to behave most ideally? - low temperature and high pressure - high temperature and high pressure - low temperature and low pressure - high temperature and low pressure

high temperature and low pressure

Which of the following electronic transitions for the hydrogen atom will produce the spectral line with the shortest wavelength? n = 1 to n = 0 n = 4 to n = 3 n = 2 to n = 1 n = 5 to n = 4 n = 3 to n = 2

n = 2 to n = 1

For a particular process q = -10 kJ and w = +25 kJ. Which statement is true? - ΔU = -35 kJ - All of these statements are true. - None of these statements are true. - Heat flows from the surroundings to the system. - The system does work on the surroundings.

none of these statements are true.

Chapter 6: Match each system description to the appropriate label: open, closed, or isolated. -A perfectly sealed thermos (vacuum flask) of soup -A thermos of soup with the lid removed -A saucepan of soup with a lid on it

open, isolated, and closed

The pressure exerted on a sample of a fixed amount of gas is doubled at constant temperature, and then the temperature of the gas in Kelvin is doubled at constant pressure. What is the final volume of the gas? -the same as the initial volume -1/2 the initial volume -twice the initial volume -four times the initial volume -1/4 the initial volume

the same as the initial volume

Thermochemistry

the study of energy changes that occur during chemical reactions and changes in state

For a given reaction, ΔHº < 0 and ΔSº > 0. Which statement is true? - ΔGº > 0 and the reaction is non-spontaneous at all temperatures. - ΔGº < 0 and the reaction is spontaneous at all temperatures. - ΔGº < 0 and the reaction is non-spontaneous at all temperatures. - ΔGº > 0 and the reaction is spontaneous at all temperatures.

ΔGº < 0 and the reaction is spontaneous at all temperatures.

For which substance is the standard entropy of formation equal to zero? -N2(l) -Na(s) -CH3OH(g) -N2(g) -ΔSfº is not equal to zero for any of these substances because perfectly crystalline solids do not exist and absolute zero cannot be achieved.

ΔSfº is not equal to zero for any of these substances because perfectly crystalline solids do not exist and absolute zero cannot be achieved.