1) A 25.0 g sample of CO 2 is placed in an 8.00 L steel tank. What is the pressu
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Question
1) A 25.0 g sample of CO2 is placed in an 8.00 L steel tank. What is the pressure in torr in the tank at 45oC?
2) At what temperature in oC would 25.0 g of NH3 in a 27 L steel tank have a pressure of 1.5 atm?
3) A sample of gas in a 35.0 L cylinder-piston assembly has a pressure of 1.55 atm at 125oC. If the pressure on the gas increases to 3.0 atm while the volume of the gas decreases to 25.0 L, what is the temperature (oC) of the gas?
4) Use the following equation to answer the questions below:
2 C2H2 (g) + 5 O2 (g) à 4 CO2 (g) + 2 H2O (g)
a) How many moles of O2 are needed to react with 15.0 mL of C2H2 at 125oC and 1.25 atm?
b) How many liters of CO2 (g) are produced from 15.0 grams of C2H2 (g) at STP?
c) How many liters of CO2 (g) at 75oC and 725 torr are produced from 27.0 L of C2H2 (g) at 175oC and 850 torr?
5) What is the partial pressure of He in a tank with a total pressure of 850 torr if it contains 0.500g of He, 1.505 g O2 , and 0.732 g N2?
6) At 35oC water has a vapor pressure of 42.2 torr. What is the partial pressure of a gas if the total pressure of the gas collected over water is 1.234 atm?
7) The value of H = -1170 kJ for the reaction as follows:
2Ba(s) + O2(g) à 2BaO(s)
a) How many kJ of heat will be released when 5.75 g of Ba reacts with enough O2?
b) How many grams of BaO will be generated if -250.0 kJ heat generated?
8) The specific heat of lead is 0.13J/g-K. How much heat is required to raise the temperature of 15 g of lead from 22oC to 37 oC?
9)A sample of aluminum metal absorbs 9.86 J of heat, upon which the temperature of the sample increases from 23.2oC to 30.5 oC. The specific heat of aluminum is 0.90 J/g-K, what will be the mass of sample?
10) How much heat is released to convert 135 grams of water at 70.0 °C to ice at -23.0 °C at 1 atm?
(Relevant data for water: normal melting point =0.0 °C, normal boiling point = 100.0 °C, Cs(ice) = 2.09 J/g·°K, Cs(H2O(l)) = 4.18 J/g·°K, Cs(H2O(g)) = 1.84 J/g·°K, DHfus = 6.01 kJ/mol, DHvap = 40.67 kJ/mol)
Explanation / Answer
PV = nRT
where:
P is the pressure of the gas
V is the volume of the gas
n is the amount of substance of gas (in moles)
R is gas constant = = 0.0821 L atm K-1 Mol-1
T is the absolute temperature of the gas.
substitute in the equation and calculate
1) A 25.0 g sample of CO2 is placed in an 8.00 L steel tank. What is the pressure in torr in the tank at 45oC?
Rearrange the Ideal Gas Law to this:
P = nRT / V
Substitute values into the equation
P = (25/44) x 0.0821 L atm K-1 Mol-1 x 318 K / 8 L
P = 1.05 atm = 805.27 Torr
2) At what temperature in oC would 25.0 g of NH3 in a 27 L steel tank have a pressure of 1.5 atm?
T = PV /nR
Substitute values into the equation
T = 1.5 atm x 27 L / (25/17) x 0.0821 = 335.444 K = 62.44 oC
3) A sample of gas in a 35.0 L cylinder-piston assembly has a pressure of 1.55 atm at 125oC. If the pressure on the gas increases to 3.0 atm while the volume of the gas decreases to 25.0 L, what is the temperature (oC) of the gas?
Let us find the moles of gas initially
n = PV /RT
n = 1.55 x 35 / 0.0821 x 398 = 1.66 Moles
Using this mole value we can calculate the temperature for new pressure and volume
T = PV /nR
T = 3 x 25 / 0.0821 x 1.66 = 550.23 K = 277.23 oC
Balanced equation:
2 C2H2(g) + 5 O2(g) = 4 CO2(g) + 2 H2O(g)
a) How many moles of O2 are needed to react with 15.0 mL of C2H2 at 125oC and 1.25 atm?
Moles of C2H2 = PV / RT = 1.25 x 0.015 / 0.0821 x 398 = 5.738 x 10-4 Mole
Moles of O2 need = 5.738 x 10-4 Mole x 5 / 2 = 0.0014345 Moles
b) How many liters of CO2 (g) are produced from 15.0 grams of C2H2 (g) at STP?
15 gm of C2H2 = 15 / 26.03 = 0.576 Moles
Moles od CO2 to be produced = 1.1521
Volume of CO2 = 1.1521 x 0.0821 x 273 / 1 = 25.822 Liter
c) How many liters of CO2 (g) at 75oC and 725 torr are produced from 27.0 L of C2H2 (g) at 175oC and 850 torr?
Moles of C2H2 = 1.118 x 27 / 0.0821 x 448 = 0.820 Moles
MOles of CO2 to be produced = 1.64 Moles
Volume of CO2 = 1.64 x 0.0821 x 348 / 0.9539 = 49.16 Liter
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