Test 4 Quiz Questions Flashcards
Energy change is the sum of heat and work: ΔE = q + w. Work is calculated by: w = -PΔV
What is the change in energy (in joules) if a reaction absorbs 33.4 J of heat and increases in volume from 0.250L to 0.750L at a constant pressure of 0.921 atm? Please include the correct sign with your numerical result.
(Note: Make sure your units are consistent when combining energy terms. The conversion factor you need is: 1 L·atm = 101.3 J)
-13.2
Which of the following will affect the amount of energy it takes to change the temperature of a solid substance by 10 °C?
Options:
1) The initial temperature of the substance
2) The specific heat capacity of the substance
3) The atmospheric pressure
4) The amount (mass) of the substance you have
2) The specific heat capacity of the substance
4) The amount (mass) of the substance you have
A piece of metal A and a piece of metal B of the same mass and at the same temperature of 80°C are dropped into seperate beakers each containing 100.0 g of water at room temperature. Once they equilibrate, you find that the beaker with the sample of metal A is warmer than the beaker with the sample of metal B. Which metal has the larger specific heat capacity?
Metal A
What is the specific heat capactiy (in J/g°C) of a substance if it requires 1,318 J of energy to change a 34.1 g sample of the substance by 48.4 °C?
0.799
How much energy (in Joules) is required to heat 12.95 g of water from 29.28 to 76.82 °C? Cwater = 4.18J/g°C
Correct!
2,573
A 13.27 g sample of an unknown hydrocarbon undergoes combustion in a bomb calorimeter with a calorimeter constant of 18.5 kJ/°C. If the calorimeter increases in temperature from 17.67 to 28.75 °C, what is the value of q (in kJ) for the combustion reaction. Include the correct sign with your value.
-205
The reaction described takes place in solution in a coffe-cup style calorimeter. We will assume that the cups absorb or release a negligible amount of heat so we will not need to worry about the calorimeter constant or qcal.
If the total mass of the solution in the calorimeter is 23.79 g and and the solution increases from 14.67 °C to 55.97 °C, what is the value of q in joules for the reaction. Include the correct sign with your value of q. C = 4.179 J/g°C for the solution.
-4,106
A reaction is done in a coffee-cup calorimeter by mixing equal volumes of reactants. If the initial temperature of the reactant solutions before then are mixed is 24.0 oC and the final temperature of the solution after the reaction has occurred is 25.2 oC, we can say that the reaction is __________ and the heat of reaction, ∆Hrxn , is written the a ___________ sign. For this reaction the enthalpy content of the products is ___________ than that of the reactants.
Options:
Negative
Positive
Exothermic
Endothermic
Higher
Lower
Negative
Endothermic
Lower
N2 (g) + 3H2 (g) → 2NH3(g) ΔH = -92.2 kJ
What mass of ammonia is theoretically produced if the above reaction released 173 kJ of heat?
63.9
2C2H6 (g) + 7O2 (g) → 4CO2(g) + 6H2O (g) ΔH = -1560 kJ
How much heat (in kJ) is released if 16.9 g of ethane ( 30.07 g/mol) undergoes combustion?
(Give your answer as a positive number, since you cannot release negative energy.)
438
If the enthalpies of formation of carbon dioxide and water are -393.509 kJ/mol and -285.83 kJ/mol respectively, what is the enthalpy of formation of C10H8(s) in kJ/mol?
C10H8(s) + 12O2(g) → 10CO2(g) + 4H2O (l) ΔHo = -5156.1 kJ
Options:
1) 77.7
2) 4476.8
3) 3619.3
4) -77.7
5) -10234.5
1) 77.7
Calculate the ∆Hrxn for the reaction below:
MgCl2 (aq) + 2 KOH (aq) —> Mg(OH)2 (s) + 2 KCl (aq)
∆Hfo for MgCl2 (aq) = -797.1 kJ/mol
∆Hfo for KOH (aq) =-424.2 kJ/mol
∆Hfo for Mg(OH)2 (s) = -924.7 kJ/mol
∆Hfo for KCl (aq) = -419.6 kJ/mol
∆Hrxno = ? kJ Don’t forget the sign and write your 4 significant figures.
-118.4
What is the enthalpy change for the first reaction?
P4(s) + 6Cl2(g) → 4PCl3(l) ΔH =
P4(s) + 10Cl2(g) → 4PCl5(s) ΔH = -1,773.5
PCl3(l) + Cl2 → PCl5(s) ΔH = -128.9
-1,257.9
What is the enthalpy change for the first reaction?
Fe2O3(s) → 2Fe(s) + 3/2O2(g) ΔH =
4Fe(s) + 3O2(g) → 2Fe2O3 (s) ΔH = -1,650 kJ
823
The specific heat of Ag is 0.235 J/g-K. The molar heat capacity of Ag ____________ J/mol-K.
(MWAg = 108 g/mol)
Options:
1) None of these answers
2) 1.41x10^23
3) 0.00218
4) 25.4
5) 0.235
4) 25.4
What is the pressure for a gas in mmHg if it has a pressure of 63.7 atm?
48,400
A pressure for a gas is measured as 758 kPa. What is the pressure in atm?
7.48
A sample of gas at a pressure of 1.85 atm and a temperature of 22.1oC is heated to 48.3oC. If the gas expanded to 2.45L from 2.07L, what is the pressure of the heated gas?
1.7
A 3.2 L sample of CO2(g) at 23.7 oC expands to what volume at 40.8 oC at a constant pressure of 0.98 atm?
3.4
A balloon contains 4.91L of helium at a temperature of 28.1oC and a pressure of 1.03 atm. What is the mass of helium in the balloon?
0.819
The solid chemicals in a specific air bag create 0.786 moles of gas. To what volume (in L) will the air bag inflate at a pressure of 1.10 atm and a temperature of 293 K.
17.2
14.6 g of butane (58.12 g/mol) undergoes combustion according to the following equation. What pressure of carbon dioxide in atm is produced at 314 K in a 1.51 L flask.
2 C4H10 (g) + 13 O2 (g) → 8 CO2 (g) + 10 H2O (g)
17.1
If 2.42 moles of nitrogen reacts with 4.78 moles of hydrogen, what is the maximum volume of ammonia (in L) that can be produced at a pressure of 1.06 atm and 322 K.
N2(g) + 3 H2(g) → 2 NH3(g)
79.4
Order the gases from most dense (1.) to least dense (5.) at 25°C and 1 atm.
Options:
F2
N2
KR
H2
Ne
1) Kr
2) F2
3) N2
4) Ne
5) H2
