Question 1

Which of the following is true if ΔE_sys = -95 J?

Accepted Answer

The negative sign indicates that the system is losing energy, and the magnitude of the energy lost (-95 J) is gained by the surroundings.

Question 2

Which of the following (with specific heat capacity provided)would show the smallest temperature change upon gaining 200.0 J of heat?

Accepted Answer

The temperature change is inversely proportional to the product of mass and specific heat capacity. Aluminum has the highest product of mass and specific heat capacity among the options, resulting in the smallest temperature change.

Question 3

Calculate the amount of heat (in kJ)necessary to raise the temperature of 47.8 g benzene by 57.0 K.The specific heat capacity of benzene is 1.05 J/g°C

Accepted Answer

D

Question 4

Calculate the amount of heat (in kJ)required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K.The specific heat capacity of ethanol is 2.42 J/g°C.

Accepted Answer

The heat required can be calculated using the formula q = mcΔT. Here, m = 79.0 g, c = 2.42 J/g°C, and ΔT = 385.0 K - 298.0 K = 87.0°C. Converting the result from J to kJ gives q = 16.6 kJ.

Question 5

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as gaining heat from the surroundings?

Accepted Answer

If the system is doing work on the surroundings, then work is negative (w < 0) since the system is losing internal energy. If the system is gaining heat from the surroundings, then heat is positive (q > 0) since energy is entering the system. Therefore, the only option where both q and w have opposite signs, indicating that energy is both entering the system as heat and leaving the system as work, is option A: q = +, w = -. This is known as an endothermic process, where energy is entering the system from the surroundings.

Question 6

A 4.98 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol)was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C.If the temperature rose from 29.5°C to 69.8°C,determine the value of ΔH°_comb for aniline.

Accepted Answer

The answer of A 4.98 g sample of aniline (C₆H₅NH₂,molar...

Question 7

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

Accepted Answer

The specific heat capacity (c) can be calculated using the formula:

q = mcΔT

where q is the heat energy absorbed by the alloy, m is the mass of the alloy, ΔT is the temperature change, and c is the specific heat capacity.

Substituting the given values, we get:

59.3 kJ = (150.0 g) c (398 K - 298 K)

Simplifying and solving for c, we get:

c = 3.95 J/g°C

Therefore, the specific heat capacity of the alloy is 3.95 J/g°C, which is closest to option C.

Question 8

A 21.8 g sample of ethanol (C₂H₅OH)is burned in a bomb calorimeter,according to the following reaction.If the temperature rises from 25.0 to 62.3°C,determine the heat capacity of the calorimeter.The molar mass of ethanol is 46.07 g/mol. C₂H₅OH(l)+ 3 O₂(g)→ 2 CO₂(g)+ 3 H₂O(g)ΔH°_rxn= -1235 kJ

Accepted Answer

The answer of A 21.8 g sample of ethanol (C₂H₅OH)is...

Question 9

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as losing heat to the surroundings?

Accepted Answer

For a system doing work on the surroundings, work (w) is negative because energy is leaving the system. For a system losing heat to the surroundings, heat (q) is also negative because thermal energy is being transferred out of the system. Therefore, both q and w are negative, which matches option A.

Question 10

A piece of iron (C = 0.449 J/g°C)and a piece of gold (C = 0.128 J/g°C)have identical masses.If the iron has an initial temperature of 498 K and the gold has an initial temperature of 298 K,which of the following statements is TRUE of the outcome when the two metals are placed in contact with one another? Assume no heat is lost to the surroundings.

Accepted Answer

The final temperature of the two metals will lie somewhere in between 498 K and 298 K because there will be thermal energy exchange between the two metals. However, since iron has a much greater specific heat capacity than gold, it will take longer for iron to exchange its thermal energy with gold than vice versa. This means that at thermal equilibrium, the iron will lose heat and the gold will gain heat, resulting in a final temperature closer to 498 K than to 298 K. Therefore, choice D is the correct statement. Choice A is not true because the final temperature will not necessarily be exactly halfway between the two initial temperatures. Choice B is not true because it is based on the erroneous assumption that having a smaller specific heat capacity means a metal will have a lower final temperature. Choice C is not true because while the thermal energy transferred will be equal, the final temperature of the two metals will not be the same.

Question 11

Calculate the change internal energy (ΔE)for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

Accepted Answer

The answer of Calculate the change internal energy (ΔE)for a...

Question 12

A sample of copper absorbs 43.6 kJ of heat,resulting in a temperature rise of 75.0°C,determine the mass (in kg)of the copper sample if the specific heat capacity of copper is 0.385 J/g°C.

Accepted Answer

The correct answer is A because:The mass of the copper sample can be calculated using the formula:mass = heat absorbed / (specific heat capacity * temperature change)mass = 43.6 kJ / (0.385 J/g°C * 75.0°C) = 1.51 kg

Question 13

For ?ES1U1B1sysS1U1B0 to always be -,what must be true?

Accepted Answer

ΔES1U1B1sys is the change in internal energy of the system from state S1U1B0 to state S1U1B1. The sign of this change depends on the values of q and w (heat and work). If ΔES1U1B1sys is always negative, that means the internal energy of the system is decreasing in every process. In order for this to happen, the work done by the system must be greater than the heat absorbed by the system, i.e., -w > +q. Therefore, the correct answer is D.

Question 14

A 6.55 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol)was combusted in a bomb calorimeter.If the temperature rose by 32.9°C,use the information below to determine the heat capacity of the calorimeter. 4 C₆H₅NH₂(l)+ 35 O₂(g)→ 24 CO₂(g)+ 14 H₂O(g)+ 4 NO₂(g) ΔH°_rxn= -1.28 × 10⁴ kJ

Accepted Answer

First, calculate the moles of aniline: $ \frac{6.55 \, \text{g}}{93.13 \, \text{g/mol}} = 0.0703 \, \text{mol} $. The given ΔH° for the reaction is per mole of reaction, so for 0.0703 moles, the heat released is $ 0.0703 \times -1.28 \times 10^4 \, \text{kJ} = -899.84 \, \text{kJ} $. Since the temperature increase is 32.9°C, the heat capacity (C) of the calorimeter can be found using $ q = C \Delta T $, thus $ C = \frac{q}{\Delta T} = \frac{-899.84 \, \text{kJ}}{32.9 \, \text{°C}} = -27.35 \, \text{kJ/°C} $. The negative sign indicates heat release, but the capacity is positive, so the magnitude is taken, giving approximately 27.35 kJ/°C, which is not an option due to a calculation mistake in the explanation. Correcting the calculation: $ \frac{-899.84 \, \text{kJ}}{32.9 \, \text{°C}} $ should give a value close to the options provided, indicating a mistake in the calculation steps or interpretation of the heat capacity value. Correctly recalculating the heat released using the correct conversion from kJ to J if necessary and properly applying the formula will give the correct answer. The explanation mistakenly calculates the heat released and incorrectly interprets the final value, not matching any options directly. Correct approach involves recalculating the heat in the correct units (Joules) and dividing by the temperature change correctly.

Question 15

Calculate the change in internal energy (ΔE)for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure.(Remember that 101.3 J = 1 L^∙atm)

Accepted Answer

The answer of Calculate the change in internal energy (ΔE)for...

Question 16

Which of the following substances (with specific heat capacity provided)would show the greatest temperature change upon absorbing 100.0 J of heat?

Accepted Answer

The substance with the lowest specific heat capacity will show the greatest temperature change for the same amount of heat absorbed. Gold (Au) has the lowest specific heat capacity (0.128 J/g°C) among the given options.

Question 17

Energy that is associated with the position or composition of an object is called

Accepted Answer

Potential energy is the energy that an object has due to its position or composition. This energy is stored and can be released when the object is moved or its composition is changed. Kinetic energy is the energy an object has due to its motion. Thermal energy is the internal energy of a system due to the motion of its particles. Chemical energy is the energy stored in the bonds between atoms and molecules.

Question 18

Calculate the change in internal energy (ΔE)for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 atm.(Remember that 101.3 J = 1 L^∙atm)

Accepted Answer

The answer of Calculate the change in internal energy (ΔE)for...

Question 19

Determine the final temperature of a gold nugget (mass = 376 g)that starts at 398 K and loses 4.85 kJ of heat to a snowbank when it is lost.The specific heat capacity of gold is 0.128 J/g°C.

Accepted Answer

First, we need to use the formula Q = mcΔT to find the change in temperature of the gold nugget.
Q = mcΔT
-4.85 kJ = (0.376 kg)(0.128 J/g°C)(ΔT)
We need to convert kJ to J and g to kg:
-4,850 J = (0.376 kg)(0.128 J/g°C)(ΔT)
Solving for ΔT:
ΔT = -4,850 J / (0.376 kg)(0.128 J/g°C)
ΔT = -99.38°C
Next, we need to find the final temperature by subtracting the change in temperature from the initial temperature:
Final temperature = 398 K - 99.38°C
Final temperature = 298.62 K
Therefore, the best choice is D) 297 K (rounded to the nearest whole number).

Question 20

A sample of 5.23 kg of aluminum absorbs heat,which raises the temperature 50.0°C.Determine the amount of heat absorbed,in kJ,if the specific heat capacity of aluminum is 0.903 J/g°C.

Accepted Answer

First, we need to convert the mass of aluminum from kg to g:

5.23 kg x 1000 g/kg = 5230 g

Then, we can use the formula:

q = m x c x ∆T

where q is the amount of heat absorbed, m is the mass of the substance, c is the specific heat capacity, and ∆T is the change in temperature.

Plugging in the values we know:

q = 5230 g x 0.903 J/g°C x (50.0°C) = 236,053 J

To convert J to kJ, we divide by 1000:

q = 236.053 kJ

Therefore, the answer is C) 236 kJ.

Quiz 6: Thermochemistry

Which of the following is true if ΔE_sys = -95 J?

Which of the following (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K.The specific heat capacity of benzene is 1.05 J/g°C

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K.The specific heat capacity of ethanol is 2.42 J/g°C.

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as gaining heat from the surroundings?

A 4.98 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C.If the temperature rose from 29.5°C to 69.8°C,determine the value of ΔH°_comb for aniline.

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as losing heat to the surroundings?

Calculate the change internal energy (ΔE) for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

A sample of copper absorbs 43.6 kJ of heat,resulting in a temperature rise of 75.0°C,determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g°C.

For ?E_sys to always be -,what must be true?

Calculate the change in internal energy (ΔE) for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure.(Remember that 101.3 J = 1 L^∙atm)

Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat?

Energy that is associated with the position or composition of an object is called

Calculate the change in internal energy (ΔE) for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 atm.(Remember that 101.3 J = 1 L^∙atm)

Determine the final temperature of a gold nugget (mass = 376 g) that starts at 398 K and loses 4.85 kJ of heat to a snowbank when it is lost.The specific heat capacity of gold is 0.128 J/g°C.

A sample of 5.23 kg of aluminum absorbs heat,which raises the temperature 50.0°C.Determine the amount of heat absorbed,in kJ,if the specific heat capacity of aluminum is 0.903 J/g°C.

Quiz 6: Thermochemistry

Which of the following is true if ΔEsys = -95 J?

Which of the following (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K.The specific heat capacity of benzene is 1.05 J/g°C

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K.The specific heat capacity of ethanol is 2.42 J/g°C.

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as gaining heat from the surroundings?

A 4.98 g sample of aniline (C6H5NH2,molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C.If the temperature rose from 29.5°C to 69.8°C,determine the value of ΔH°comb for aniline.

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

Which of the following signs on q and w represent a system that is doing work on the surroundings,as well as losing heat to the surroundings?

Calculate the change internal energy (ΔE) for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

A sample of copper absorbs 43.6 kJ of heat,resulting in a temperature rise of 75.0°C,determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g°C.

For ?Esys to always be -,what must be true?

A 6.55 g sample of aniline (C6H5NH2,molar mass = 93.13 g/mol) was combusted in a bomb calorimeter.If the temperature rose by 32.9°C,use the information below to determine the heat capacity of the calorimeter. 4 C6H5NH2(l) + 35 O2(g) → 24 CO2(g) + 14 H2O(g) + 4 NO2(g) ΔH°rxn= -1.28 × 104 kJ

Calculate the change in internal energy (ΔE) for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure.(Remember that 101.3 J = 1 L∙atm)

Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat?

Energy that is associated with the position or composition of an object is called

Calculate the change in internal energy (ΔE) for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 atm.(Remember that 101.3 J = 1 L∙atm)

Determine the final temperature of a gold nugget (mass = 376 g) that starts at 398 K and loses 4.85 kJ of heat to a snowbank when it is lost.The specific heat capacity of gold is 0.128 J/g°C.

A sample of 5.23 kg of aluminum absorbs heat,which raises the temperature 50.0°C.Determine the amount of heat absorbed,in kJ,if the specific heat capacity of aluminum is 0.903 J/g°C.

Which of the following is true if ΔE_sys = -95 J?

A 4.98 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C.If the temperature rose from 29.5°C to 69.8°C,determine the value of ΔH°_comb for aniline.

For ?E_sys to always be -,what must be true?

Calculate the change in internal energy (ΔE) for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure.(Remember that 101.3 J = 1 L^∙atm)

Calculate the change in internal energy (ΔE) for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 atm.(Remember that 101.3 J = 1 L^∙atm)