AP CHEMISTRY UNIT 5 - decreases from 95.1C to 30.0C. Calculate the he...

AP CHEMISTRY UNIT 5

• You take 295.5 g of a solid at 30.0C and let it melt in 425 g of water. The water temp decreases from 95.1C to 30.0C. Calculate the heat of fusion of this solid.: C. 331 J/g • The enthalpy of fusion of ice is 6.020 kJ/mol. The heat capacity of liquid water is 75.4 J/mol*C. What is the smallest number of ice cubes at 0C, each containing one mole of water,

necessary to cool 500 g of liquid water from 20C to 0C?: B. 7

• 30.0mL of pure water at 282K is mixed with 50.0mL of pure water at 306K. What is the

final temperature of the mixture?: B. 297 K

• Consider the reaction H2(g) + 1/2O2(g) = H2O(l) DeltaH= -286 kJ Which of the

following is true?: E. Both A and C are true

• In the lab, you mix two solutions (each originally at the same temperature) and the temperature of the resulting solution decreases. Which of the follow- ing is true?: C. The chemical reaction is absorbing energy.• What is the specific heat capacity of a metal if it requires 178.1 J to change the temperature

of 15.0 g of the metal from 25C to 32C?: D. 1.70 J/g*C

• A 140.0 g sample of water at 25C is mixed with 11.7 g of a certain metal at 100.0C. After thermal equilibrium is established, the (final) temperature of the mixture is 29.6C. What is the specific heat capacity of the metal, assuming it is constant over the temperature range

concerned?: A. 0.34 J/g*C

• If 5.0 kJ of energy is added to a 15.5 g sample of water at 10C, the water is: E. still a liquid • Exactly 123.7 J will raise the temperature of 10.0g of a metal from 25C to 60C. What is

the specific heat capacity of the metal?: B. 0.353 J/g*C

• A chunk of lead at 91.6C was added to 200.0g of water at 15.5C. The specific heat of lead is 0.129 J/g*C and the specific heat of water is 4.18. When the temp stabilized, the temperature of

the mixture was 17.9C. What was the mass of lead added?: D. 211 g

• On a cold winter day, a steel metal fence post feels colder than a wooden fence post of identical size because: B. The specific heat capacity of steel is lower than the specific heat capacity of wood • What is the specific heat capacity of silver if it requires 86.3 J to raise the temp of 15 g of

silver by 25C?: B. 0.23 J/g*C

• A 4.4 g sample of Colorado oil shale is burned in a bomb calorimeter, which causes the temperature of the calorimeter to increase by 5C. The calorimeter contains 1.00 kg of water (c=4.184) and the heat capacity of the empty calorimeter is 0.10 kJ/C. How much heat is

released per gram of oil shale when it is burned?: D. 4.9 kJ/g

• If a student performs an endothermic reaction in a calorimeter, how does the calculated value of DeltaH from the actual value if the heat exchanged with the calorimeter is not taken into account?: D. DeltaHcalc would be less positive because the reaction absorbs heat from the 1 / 2

calorimeter • A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.109 g sample of ethylene (C2H4) was burned in this calorimeter, the temperature increased by 2.22K. Calculate the

energy of combustion fo rone mole of ethylene.: E.

-1.41*10^3 kJ/mol

• Consider the reaction: C2H5OH(l) + 3O2(g) = 2CO2(g) + 3H2O(l), DeltaH=

-1.37*10^3 kJ When a 21.1 g sample of ethyl alcohol (molar mass= 46.07 g/mol) is burned, how

much energy is released as heat?: C. 6.26*10^2 kJ

• The DeltaH value for the reaction 1/2O2(g) + Hg(l) = HgO(s) is -90.8 kJ. How much heat is

release when 66.9 g Hg is reacteddd with oxygen?: C. 30.3. kJ

• The total volume of hydrogen gas needed to fill the Hindenburg was 2.11*10^8 L at 1.00 atm and 24.7C. How much energy was evolved when it burned? H2(g)+1/2O2(g) = H2O(l),

DeltaH= -286kJ: D. 2.47*10^9 kJ

• CH4(g) + 4Cl2(g) = CCl4(g) + 4HCl(g), DeltaH= -434 kJ Based on the above reaction, what energy change occurs when 1.2 moles of methane reacts?: A. 5.2*10^6 J are released • Given the equation S(s) + O2(g) = SO2(g), DeltaH=-296 kJ, which of the following statements are true? I. The reaction is exothermic. II. When 0.500 mole sulfur is reacted, 148 kJ of energy is released. III. When 32g of sulfur are burned, 2.96*10^5 J of energy is released.:

• All are true

• When 0.236 mol of a weak base (A-) is reacted with excess HCl, 6.991 kJ of energy is released as heat. What is DeltaH for this reaction per mole of A- consumed?: C. -29.3 kJ • What is the enthalpy change when 49.4 mL of 0.430 M sulfuric acid reacts with 23.3 mL of 0.309 M potassium hydroxide? H2SO4(aq) + 2KOH(aq) = K2SO4(aq) + 2H2O(l), DeltaH=

-111.6 kJ/mol: A. -0.402 kJ

• How much heat is liberated at constant pressure when 2.35 g of potassium metal reacts with 5.68 mL of liquid iodine monochloride (d=3.24 g/mL)? 2K(s)

+ ICl(l) = KCl(s)+KI(s), DeltaH= -740.71 kJ/mol: D. 2.23*10^1 kJ

• Consider the following specific heats of metals (list) If the same amount of heat is added to 25g of each of the metals, which are all at the same initial temp, which metal will have the

highest temp?: E. Lead

• A gas absorbs 0.0 J of heat and then performs 30.7 J of work. The change in internal energy

of the gas is: D. -30.7 J

• What is the kinetic energy of a 1.56 kg object moving at 94.0 km/hr?: A. 5.32*10^2 kJ • Which of the following statements correctly describes the signs of q and w for the following exothermic process at P= 1 atm and T= 370K?: C. q is negative, w is positive

• / 2