chem 11 exams 2

DEPARTMENT OF PHYSICAL SCIENCES KINGSBOROUGH COMMUNITY COLLEGE OF THE CITY UNIVERSITY OF NEW YORKEXAM 2 CHEM 1100 WINTER 2013 P. LLOYD

1. Solid potassium carbonate reacts with aqueous hydrochloric acid to form aqueous potassium chloride, water, and gaseous carbon dioxide. A 0.550 g sample of potassium carbonate produced carbon dioxide gas that is collected using water displacement at 767 torr and at 23 C. What is the volume in milliliters of carbon dioxide gas produced?

2. The gas pressure in a steel container can is 1.25 atm at 25 C. If we assume that the gas obeys the ideal-gas equation, what is the pressure in torr when the can is heated to 425 C?

3. A flask initially has a mass of 115.011 g. When the flask is filled with an unknown gas to a pressure of 1.025 atm at 20 C, its mass increases to 116.112 g. The volume of the flask is measured and found to be 450. mL. Assuming the ideal gas law equation applies, calculate the approximate molar mass of the gas.

4. A mixture of 3.00 g of fluorine gas and 3.00 g of nitrogen gas is placed in a 15.0 L vessel at 50 C. What is the partial pressure of each gas and what is the total pressure of the mixture?

5. An unknown gas composed of a monatomic element effuses at a rate that is 1.87 times the rate of chlorine gas at the same temperature. Calculate the molar mass of the unknown gas and identify it.

6. How much heat in kilojoules is released when 0.514 g of propane is burned (combusted) in oxygen gas.

7. How much heat in kilojoules is needed to warm 2.500 g of copper from -12 C to 199 C?

8. The burning of gunpowder involves the oxidation of charcoal (approximated as C7H4O) using potassium nitrate as an oxidizing agent. The reaction produces several gases:

4 KNO3 (s) + C7H4O (s) + 2 S (s) 2 K2S (s) + 4 CO2 (g) + 3 CO (g) + 2 H2O (l) + 2 N2 (g)

When 0.150 g of gunpowder is reacted in a bomb calorimeter, the temperature of the calorimeter increases from 21.50 C to 27.50 C. In a separate experiment, the heat capacity of the calorimeter is measured to be 6.055 kJ/C. Calculate the heat of reaction for the reaction per gram of gunpowder.

9. Use the following reactions:

2 Sr (s) + O2 (g) 2 SrO (s) ∆H = -1184 kJSrCO3 (s) SrO (s) + CO2 (g) ∆H = 234 kJC (graphite) + O2 (g) CO2 (g) ∆H = -394 kJ

To find the heat of reaction for:Sr (s) + C (graphite) + 3/2 O2 (g) SrCO3 (s) ∆H = ?

10. Calculate the enthalpy change for the combustion of 1.0 mol of octane.


9. -1220 kJ10. -5496 kJ


1. Solid potassium chlorate decomposes upon heating to solid potassium chloride and oxygen gas. A 8.750 g sample of potassium chlorate decomposed in a reaction and the resulting oxygen gas was collected using water displacement (vapor pressure of water is 21.5 torr) at 757 torr and at 25 C. What volume of oxygen gas was collected?

2. The gas pressure in a steel container can is 11.5 atm at 450 C. Assuming that the gas obeys the ideal-gas equation, what is the pressure when the can is cooled to 25 C?

3. A flask initially has a mass of 117.252 g. When the flask is filled with an unknown gas to a pressure of 0.967 atm at 25 C, its mass increases to 120.456 g. The volume of the flask is measured and found to be 450. mL. Assuming the ideal gas law equation applies, calculate the molar mass of the gas.

4. A mixture of 6.00 g of helium gas and 9.00 g of nitrogen gas is placed in a 15.0 L vessel at 0 C. What is the partial pressure of each gas and what is the total pressure of the mixture?

5. An unknown gas composed of a diatomic element effuses at a rate that is 0.324 times the rate of helium gas at the same temperature. Calculate the molar mass of the unknown and identify it.

6. How much heat in kilojoules is released when 5.25 g of ethane is burned (combusted) in oxygen gas.

7. How much heat in kilojoules is needed to warm 25.00 g of water from 2 C to 99 C (near its boiling point).

8. The decomposition of nitroglycerine (C3H5N3O9), an explosive, produces N2 (g), CO2 (g), H2O (g), and O2 (g):

4 C3H5N3O9 (l) 6 N2 (g) + 12 CO2 (g) + 10 H2O (l) + O2 (g)

When 5.00 g of nitroglycerine is reacted in a bomb calorimeter, the temperature of the calorimeter increases from 22.00 C to 28.50 C. In a separate experiment, the heat capacity of the calorimeter is measured to be 8.505 kJ/C. Calculate the heat of reaction for the reaction of one mole of nitroglycerine.

9. Find the heat of reaction for

NO2(g) + (7/2) H2(g) 2 H2O(l) + NH3(g)

Using the following two equations:

2NH3(g) N2(g) + 3H2(g) ΔH° = +92 kJ (1/2) N2(g) + 2H2O(l) NO2(g) + 2H2(g) ΔH° = +170 kJ

10. Calculate the enthalpy change for the combustion of 1.0 mol of pentane (C5H12).


NA = 6.022 x 1023

1 amu = 1.661 x 10-24 g1 J = 1 kgm2/s2

1 kg = 1000 g1 kJ = 1000 J1 L = 1000 mL1 atm = 760 torr1 torr = 1 mm Hg1 atm = 14.7 psi1 atm = 101.325 kPaTK = TC + 273R = 0.0821 L atm/(mol·K)R = 8.31 J/(mol·K)P = F/APV = nRTP1V1/T1 = P2V2/T2

STP = 1 atm and 0 CVstp = 22.41·nM = dRT/Pvrms = 3RT/MPTOT = PA + PB + PC +…PA = XA·PTOT

XA = nA/ntot

r2/r1 = M 1/ M 2

101.3 J = 1 L·atmE = q + wH = E + PV = qp

q = msTHrxn = ∑ (np

Hf,p) – ∑ (nr Hf,r)

ANSWERS1. 2.71 L2. 4.74 atm3. 180 g/mol4. PHe = 2.24 atmPN2 = 0.479 atmPTot = 2.72 atm5. M = 38 g/mol = F2

6. 272 kJ of heat is released7. 101 kJ8. 1.8 kJ/mol9. -216 kJ/mol10. -3509 kJ/mol

specific heats (J/gC)water 4.184ethanol 2.46aluminum 0.900iron 0.444mercury 0.139copper 0.385gold 0.129

∆H Heats of formation (kJ/mol)H2O (l) -285.8H2O (g) -241.8CO2 (g) -393.5

n-ALKANESCH4 (g) -74.85C2H6 (g) -84.7C3H8 (g) -103.9C4H10 (g) -124.7C5H12 (g) -173.5C6H14 (l) -199.4C7H16 (l) -222.5C8H18 (l) -223.8

ALKENESC2H4 (g) 52.3C3H6 (g) 20.4

ALKYNESC2H2 (g) 226.6

ALCOHOLSCH3OH (l) -238.7C2H5OH (l) -276.98

SUGARSC6H12O6 (s) -1274.5C12H22O11 (s) -2221.7

ARMOMATICSBenzene C6H6 (l) 49.0Naphthalene C10H8 (s) 77.0

DEPARTMENT OF PHYSICAL SCIENCES KINGSBOROUGH COMMUNITY COLLEGE OF THE CITY UNIVERSITY OF NEW YORKEXAM 2 CHEM 1100 FALL 2012 P. LLOYD

1. Solid calcium carbonate decomposes upon heating to solid calcium oxide and carbon dioxide gas. A 5.25 g sample of calcium carbonate decomposed in a reaction and the resulting carbon dioxide gas was collected at 1.3 atm and 31 C. What volume of carbon dioxide gas was collected?

2. The gas pressure in an aerosol can is 1.5 atm at 25 C. Assuming that the gas obeys the ideal-gas equation, what is the pressure when the can is heated to 450 C?

3. A flask initially has a mass of 134.567 g. When the flask is filled with an unknown gas to a pressure of 0.967 atm at 31 C, its mass increases to 137.456 g. The volume of the flask is measured and found to be 936 mL. Assuming the ideal gas law equation applies, calculate the molar mass of the gas.

4. A mixture of 6.00 g of oxygen gas and 9.00 g of methane gas is placed in a 15.0 L vessel at 0 C. What is the partial pressure of each gas and what is the total pressure of the mixture?

5. An unknown gas composed of a diatomic element effuses at a rate that is 0.355 times the rate of oxygen gas at the same temperature. Calculate the molar mass of the unknown and identify it.

6. How much heat in kilojoules is released when 4.50 g of methane is burned (combusted) in oxygen gas.

7. How much heat in kilojoules is needed to warm 250 g of water (about 1 cup) from 22 C (about room temperature) to 98 C (near its boiling point).

8. The combustion of methylhydrazine (CH6N2), a liquid rocket fuel, produced N2 (g), CO2 (g) and H2O (l):

2 CH6N2 (l) + 5O2 (g) 2N2 (g) + 2CO2 (g) + 6H2O (l)

When 4.00 g of methylhydrazine is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.00 C to 39.50 C. In a separate experiment, the heat capacity of the calorimeter is measured to be 7.794 kJ/C. Calculate the heat of reaction for the combustion of one mole of CH6N2.

9. Calculate the enthalpy change for the reaction:P4O6 (s) + 2O2 (g) P4O10 (s)

Given the following enthalpies of reactionP4 (s) + 3O2 (g) P4O6 (s) H = -1640.1 kJP4 (s) + 5O2 (g) P4O10 (s) H = -2940.1 kJ

10. Calculate the enthalpy change for the combustion of 1 mol of benzene (C6H6 (l)).

DEPARTMENT OF PHYSICAL SCIENCES KINGSBOROUGH COMMUNITY COLLEGE OF THE CITY UNIVERSITY OF NEW YORKEXAM 2 CHEM 1100 FALL 2012 P. LLOYD

NA = 6.022 x 1023

1 amu = 1.661 x 10-24 g1 J = 1 kgm2/s2



XA = nA/ntot

r2/r1 = M 1/ M 2

101.3 J = 1 L·atmE = q + wH = E + PV = qp


Hf,p) – ∑ (nr Hf,r)ANSWERS1. 1.01 L2. 3.6 atm3. 79.7 g/mol4. PO2 = 0.281 atmPCH4 = 0.838 atmPTot = 1.12 atm5. M = 254 g/mol = I2

6. -249.6 kJ of heat is released7. 79.5 kJ8. -1300 kJ/mol9. -1300 kJ/mol10. 3267 kJ/mol




ALKENESC2H4 (g) 52.3C3H6 (g) 20.4



SUGARSC6H12O6 (s) -1274.5C12H22O11 (s) -2221.7

ARMOMATICSBenzene C6H6 (l) 49.0Naphthalene C10H8 (s) 77.0

General Chemistry 1, Summer 2012, P. Lloyd, Exam 2, July 10, 2012. Section D50A.Department of Physical Sciences Kingsborough Community College Instructor: P. Lloyd

General Chemistry 1, Summer 2012, P. Lloyd, Exam 2, July 10, 2012. Section D50A.Department of Physical Sciences Kingsborough Community College Instructor: P. Lloyd

1. A sample of air occupies 540 mL when the pressure is 1.2 atm. What volume does the air occupy at 15 atm if the temperature is unchanged? 2. A gas at 772 mm Hg and 35.0 C occupies a volume of 6.85 L. Calculate its volume at STP.

3. A 2.10 L vessel contains 4.65 g of a gas at 0.970 atm and 21.0 C. Calculate the molar mass of the gas.

4. Nitrogen gas reacts with hydrogen gas to form gaseous ammonia (NH3). If 10.00 g of hydrogen reacts with excess nitrogen, what volume of ammonia is produced at 50 C and 1.50 atm?

5. Calculate the root-mean-square velocity of sulfur trioxide gas at 200 C.

6. Find the heat of combustion for pentane (C5H12) using the standard heat of formation table.

7. A 125.0 g sample of an unknown metal at 92 C is dropped into a 250 g sample of liquid water at 23.5 C. One the mixture equilibrates the temperature is 27.0 C. Calculate the specific heat capacity of the metal and identify which metal it is.

8. Nitrogen monoxide reacts with oxygen to form nitrogen dioxide. Write the balanced chemical equation for this reaction. The heat of reaction for this process is -56.55 kJ/mol. Calculate the heat produce in the reaction when 10.00 g of nitrogen monoxide is combined with 10.00 g of oxygen.

9. Calculate the heat of reaction for: H2 (g) + Cl2 (g) 2HCl (g)

Given the following: NH3 (g) + HCl (g) NH4Cl (s) H = -176 kJ N2 (g) + 3H2 (g) 2NH3 (g) H = -92 kJ N2 (g) + 4H2 (g) + Cl2 (g) 2NH4Cl (s) H = -629 kJ

10. A 466-g sample of water is heated from 18 C to 75 C. Calculate the amount of heat in kilojoules absorbed by the water.

GENERAL CHEMISTRY 1 EXAM 2 LLOYD FALL 2011 D02B

NA = 6.022 x 1023

1 amu = 1.661 x 10-24 g1 J = 1 kgm2/s2



XA = nA/ntot

r2/r1 = M 1/ M 2

101.3 J = 1 L·atmE = q + wH = E + PV = qp







ALKENESC2H4 (g) 52.3C3H6 (g) 20.4



SUGARSC6H12O6 (s) -1274.5C12H22O11 (s) -2221.7

ANSWERS TO EXAM 21. 42.3 mL2. 6.17 L3. 55.1 g/mol4. 58.3 L5. 384 m/s6. -3,508.8 kJ7. 0.450 J/gC Iron8. -18.8 kJ9. -185 kJ10. 111 kJ


(Each question is scored at 5 points)

1. Calculate the volume in liters of 5.00 g of chlorine gas (Cl2) at STP.

2. Calculate the pressure in atm of 15.00 g of methane gas (CH4) with a volume of 1.50 L when the temperature is -100 C.

3. Calculate the density in grams per liter of an unknown gas when 0.10 mol of the gas with a mass of 3.200 grams is placed in a container at 0.990 atm and 55 C.

4. A 5.0 L volume in liters of methane gas (CH4) at 50C is cooled to -50C at constant pressure. Calculate what happens to the volume of the gas.

5. Calculate the volume in liters of carbon dioxide (CO2) in liters at 25C and 2.0 atm produced when 16.00 g of ethyne (C2H2) reacts with excess oxygen.2C2H2 (g) + 5O2 (g) 4CO2 (g) + 2H2O (l)

6. A gas at -25C has a root-mean-square average velocity of about 380 m/s. Find the molar mass of the gas in grams per mole.

7. Calculate the heat produced in kilojoules when 50.00 g of propane (C3H8) reacts in excess oxygen.C3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (l) ∆H = -2221 kJ/mol

8. A 50.00 g piece of copper is cooled from 85.85 C to 15.55 C. Calculate the amount of heat in kilojoules lost by the copper.

9. A 25.00 g sample of gold initially at 98.50 C is placed into a 75.00 g pool of water at 21.50°C. What is the temperature in degrees Celsius of the metal and water after they come to thermal equilibrium?

10. Find the heat of reaction in kilojoules for the reaction:C6H12O6 (s) + 6O2 (g) 6CO2 (g) + 6H2O (l)

11. Find the heat of reaction in kilojoules for the conversion of graphite, C(graphite), into diamond, C (diamond):C (graphite) C (diamond)given that:1. C (graphite) + O2 (g) CO2 (g) ∆H = -394 kJ/mol2. C (diamond) + O2 (g) CO2 (g) ∆H = -396 kJ/mol


NA = 6.022 x 1023

1 amu = 1.661 x 10-24 g1 kg = 1000 g1 L = 1000 mL1 atm = 760 torr1 torr = 1 mm Hg1 atm = 14.7 psi1 atm = 101.325 kPaTK = TC + 273R = 0.0821 L atm/(mol·K)R = 8.31 J/(mol·K)PV = nRTP1V1/T1 = P2V2/T2

STP = 1 atm and 0 CVstp = 22.41·nMM = dRT/Purms = (3RT/MM)1/2

PTOT = PA + PB + PC +…PA = XA·PTOT

XA = nA/ntot

r2/r1 = (MM1/MM2)1/2

101.3 J = 1 L·atmE = q + wH = E + PV = qp




∆H Heats of formation (kJ/mol)H2O (l) -285.8H2O (g) -241.8CO2 (g) -393.5CH4 (g) -74.85C2H2 (g) 226.6C2H4 (g) 52.3C2H6 (g) -84.7C3H8 (g) -103.9C4H10 (g) -124.7C6H6 (l) 49.04CH3OH (l) -238.7C2H5OH (l) -276.98C6H12O6 (s) -1274.5C12H22O11 (s) -2221.7

ANSWERS1. 1.58 L2. 8.85 atm3. 1.18 g/L4. 3.45 L5. 15.0 L6. 44.01 g/mol7. -2518 kJ8. -1.35 kJ9. 22.28°C10. -2801.3 kJ11. +2 kJ

chem 11 exams 2

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