Show the calculation of the final temperature of the mixture when a 40.5 gram sample of water at 85.7oC is added to a 36.8 gram sample of water at 26.3oC in a coffee cup calorimeter.
c (water) = 4.184 J/g oC
Show the calculation of the energy involved in melting 120 grams of ice at 0oC if the Heat of Fusion for water is 0.334 kJ/g.
Thermochemical Equation Problems
Sulfur undergoes combustion to yield sulfur trioxide by the following reaction equation:
2 S + 3 O2 → 2 SO3 ΔH = - 792 kJ
If 42.8 g of S is reacted with excess O2, what will be the amount of heat given off?
Thermochemical Equation Problems
Hydrosulfuric acid (H2S) undergoes combustion to yield sulfur dioxide and water by the following reaction equation:
2 H2S + 3 O2 → 2 SO2 + 2 H2O
What is the ΔH of the reaction if 26.2 g of H2S reacts with excess O2 to yield 431.8 kJ?
Measuring Heat of Reaction Problems
A sample of benzene (C6H6), weighing 7.05 g underwent combustion in a bomb calorimeter by the following reaction:
2 C6H6 (l) + 15 O2 (g) → 12 CO2 (g) + 6 H2O (l)
The heat given off was absorbed by 500 g of water and caused the temperature of the water and the calorimeter to rise from 25.00 to 53.13 oC. The heat capacity of water = 4.18 J/g/oC and the heat capacity of the calorimeter = 10.5 kJ/oC. (1) what is the ΔH of the reaction? Using the definitions at the beginning of the module describe (2) the calorimeter + contents, (3) the type of process.
Measuring Heat of Reaction Problems
A sample of 14.5 g of sodium bicarbonate (NaHCO3) was dissolved in 100 ml of water in a coffee-cup calorimeter with no lid by the following reaction
NaHCO3 (s) → Na+ (aq) + HCO3- (aq)
If the temperature of the water and the calorimeter (heat capacity of calorimeter = 150 J/oC) decreases from 25.00oC to 19.86oC, (1) what is the ΔH of the reaction? Using the definitions at the beginning of the module describe (2) the calorimeter + contents, (3) the type of process.
Hess' Law Problems
The combustion of ammonia by the following reaction yields nitric oxide and water
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)
Determine the heat of reaction (ΔHrxn) for this reaction by using the following thermochemical data:
N2 (g) + O2 (g) → 2 NO (g) ΔH = 180.6 kJ
N2 (g) + 3 H2 (g) → 2 NH3 (g) ΔH = - 91.8 kJ
2 H2 (g) + O2 (g) → 2 H2O (g) ΔH = - 483.7 kJ
Heat of Formation Problems
Determine the heat of reaction (ΔHrxn) for the combustion of ethanol (C2H5OH) by using heat of formation data:
C2H5OH (l) + 3 O2 (g) → 2 CO2 + 3 H2O (g)
A gas sample has an original volume of 680 ml when collected at 720 mm and 28oC. What will be the volume of the gas sample if the pressure increases to 820 mm and the temperature increases to 55oC?
A gas sample containing 0.546 mole collected at 700 mm and 25oC. would occupy what volume?
GAS VOLUME STOICHIOMETRY PROBLEMS
The combustion of ethanol (C2H5OH) takes place by the following reaction equation.
C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g)
What is the volume of CO2 gas produced by the combustion of excess ethanol by 23.3 grams of O2 gas at 25oC and 1.25 atm?
PARTIAL PRESSURE - MOLE FRACTION PROBLEMS
A mixture of gases consists of 4.00 moles of He, 2.00 moles of H2, 3.00 moles of CO2 and 5.00 moles of Ar. The total pressure of the mixture is 2900 mm. Determine the mole fraction of each gas in the mixture. Determine the mole percent of each gas in the mixture. Determine the partial pressure of each gas in the mixture.
COLLECTION OF GASES OVER WATER PROBLEMS
A sample of hydrogen (H2) gas is collected over water at 35oC and 725 mm. The volume of the gas collected is 72.0 ml. How many moles of H2 gas has been collected? How many grams of H2 gas has been collected?
EFFUSION AND DIFFUSION PROBLEMS
The rate of effusion of nitrogen gas (N2) is 1.253 times faster than that of an unknown gas. What is the molecular weight of the unknown gas?