Question 1

The heating curve for a substance is shown below.The substance initially is a solid.It then becomes a liquid and a gas.Which of the line segments (I-V)represents the solid to liquid phase transition?

Accepted Answer

Line segment II represents the solid to liquid phase transition. This is because during this segment, the substance is increasing in temperature while remaining in the solid phase until it reaches its melting point. Once it reaches its melting point, it begins to absorb heat but remains at the same temperature until all the solid has melted, indicating the phase transition from solid to liquid.

Question 2

Which of the following statements regarding water and its heat capacity is true?

Accepted Answer

Water has an unusually high heat capacity because it has many ways to disperse heat flowing into it. This is primarily due to the formation of hydrogen bonds between water molecules, which allows for the absorption and distribution of a large amount of heat energy. Ice, on the other hand, has a lower heat capacity than liquid water because its rigid crystalline structure limits the ability of molecules to move and disperse heat energy. Hydrogen bonding in water plays a significant role in its high heat capacity, as it requires a large amount of energy to break these bonds and increase the temperature of the water. Steam, like ice, also has a lower heat capacity than liquid water because its molecules are more spread out and have fewer interactions with each other.

Question 3

You devise an experiment to use the condensation of acetone vapor (58.1 g/mol,boiling point 56°C)to provide enough thermal energy to heat 0.180 kilograms of water at 56.0°C to steam at 100.0°C.About how many grams of acetone vapor at 56.0°C would be required? [acetone $\Delta$H_vap = 31.3 kJ/mol; water $\Delta$H_vap = 40.7 kJ/mol; c_p(water)= 4.18 J/(g.°C); C_p(acetone vapor)= 1.29 J/(g.°C)]

Accepted Answer

To solve this, calculate the energy needed to heat water from 56°C to 100°C and then vaporize it. Then, calculate the energy released by condensing acetone vapor. Equate the two to find the mass of acetone needed.

Question 4

Find the minimum amount of energy it takes to raise 1.00 pound of lead (454 g)from room temperature (25°C)to its melting point (327°C)and then melt it.The specific heat capacity of lead is 0.159 J/(g.°C),the enthalpy of fusion is 24.7 J/g,and the molar mass is 207 g/mol.

Accepted Answer

The answer of Find the minimum amount of energy it...

Question 5

How much energy is required to convert 2.785 moles of liquid ammonia at -50.00°C to gas at 25.00°C? [C_p(liquid)= 80.80 J/(mol.°C); C_p(gas)= 35.06 J/(mol.°C); $\Delta$H_vap = 23.35 kJ/mol at the normal boiling point of -33.34°C]

Accepted Answer

First, we need to calculate the energy required to raise the temperature of liquid ammonia from F1F1F1S1F1F1F1050.00°C to its normal boiling point of F1F1F1S1F1F1F1033.34°C: (80.80 J/(molF1F1F1S1F1F1F10°C)) x (2.785 mol) x (33.34°C) = 7500 J Next, we need to calculate the energy required to vaporize the liquid ammonia at its normal boiling point: (23.35 kJ/mol) x (2.785 mol) = 65.0185 kJ Finally, we need to calculate the energy required to cool the gaseous ammonia from its boiling point at F1F1F1S1F1F1F1033.34°C to 25.00°C: (35.06 J/(molF1F1F1S1F1F1F10°C)) x (2.785 mol) x (1008.34°C) = 9824.8 J Adding up all the required energies gives: 7500 J + 65.0185 kJ + 9824.8 J = 74.48 kJ. Therefore, the answer is A.

Question 6

How much energy is needed to change the temperature of 275 grams of lead from 10.0°C to 95.0°C? [C_p = 26.7 J/(mol.°C)]

Accepted Answer

To calculate the energy needed, use the formula q = m * C * ΔT. First, convert the mass of lead to moles using its molar mass (207.2 g/mol). Then, calculate the energy using the specific heat capacity and the temperature change.

Question 7

A 19.5 g piece of titanium [c_p = 0.523 J/(g.°C)] is heated and then submerged in 1.50 $\times$ 10² grams of water [c_p = 4.18 J/(g.°C)] initially at 22.7°C.The final temperature comes to 23.7°C.What was the initial temperature of the Ti metal?

Accepted Answer

The answer of A 19.5 g piece of titanium [c_p...

Question 8

The energy content of a Big Mac is 540 Cal.How much water can be heated from 25°C to 95°C by this amount of energy? [d(water)= 1.00 g/mL,c_p (water)= 4.18 J/(g.°C),1 Cal = 4.184 kJ]

Accepted Answer

The energy in a Big Mac is 540 Cal, which is equivalent to 540 x 4.184 kJ = 2260.56 kJ. To find the mass of water that can be heated, use the formula q = mcΔT. Rearranging gives m = q / (cΔT). Here, q = 2260.56 kJ = 2260560 J, c = 4.18 J/g°C, and ΔT = 95°C - 25°C = 70°C. Solving gives m = 2260560 J / (4.18 J/g°C * 70°C) = 7700 g, which is equivalent to 7.7 L of water.

Question 9

Given equal masses of the following,which will cool the fastest from the same initial temperature?

Accepted Answer

The copper pot will cool the fastest because it has the lowest specific heat capacity (0.39 J/(g°C)), meaning it requires less energy to change its temperature compared to the other materials.

Question 10

What will be the final temperature of a 10.0 g piece of iron [C_p = 25.09 J/(mol.°C)] initially at 25°C,if it is supplied with 9.5 J from a stove?

Accepted Answer

We can use the formula q = m*c*ΔT to calculate the change in temperature of the iron, where q is the heat supplied to the iron, m is the mass of the iron, c is the specific heat of iron, and ΔT is the change in temperature.

Rearranging the formula, we can solve for ΔT:

ΔT = q/(m*c)

Plugging in the given values, we get:

ΔT = 9.5 J / (10.0 g * 25.09 J/(mol*K) * (55.85 g/mol))

ΔT = 0.00716 K

Therefore, the final temperature of the iron is:

Tfinal = Tinitial + ΔT

Tfinal = 25°C + 0.00716 K

Tfinal = 27°C

Therefore, the best choice is B) 27°C, as this is the final temperature of the iron after being supplied with 9.5 J of heat.

Question 11

Which of the following statements regarding heating curves is incorrect?

Accepted Answer

This statement is incorrect. When a substance undergoes a phase change, there is a transfer of energy without a change in temperature, as the energy is being used to break or form intermolecular bonds rather than increase the kinetic energy of the particles.

Question 12

A heating curve for some substance is shown below.Which of the line segments (I-V)represents heating of the liquid?

Accepted Answer

The answer of A heating curve for some substance is...

Question 13

Water has a molar heat capacity of 75.38 J/(mol.°C)and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to boil 72.0 grams of water at 100°C?

Accepted Answer

First, we need to calculate the amount of energy needed to vaporize 72.0 grams of water:
moles of water = mass/molar mass = 72.0 g / 18.015 g/mol = 3.996 mol
energy needed = moles of water x vaporization enthalpy = 3.996 mol x 40.7 kJ/mol = 163 kJ
Next, we need to calculate the amount of energy needed to raise the temperature of 72.0 grams of water from 0°C to 100°C:
energy needed = mass x specific heat capacity x change in temperature
= 72.0 g x 4.184 J/(g°C) x 100°C = 30.0 kJ
Finally, we add the two amounts of energy:
total energy needed = 163 kJ + 30.0 kJ = 193 kJ, which is closest to choice D (163 kJ).

Question 14

A 1.20 kg piece of granite [c_p = 0.790 J/(g.°C)] at 60.0°C must be cooled to 24.0°C by submersion in water.How much water [c_p = 4.18 J/(g.°C)] initially at 18°C would be required?

Accepted Answer

The answer of A 1.20 kg piece of granite [c_p...

Question 15

At a certain elevation,the boiling point of water is 98.5°C.How much energy is needed to heat 35.0 mL of water from 23.4°C to the boiling point at this elevation? [C_p = 75.38 J/(mol.°C),d = 1.00 g/mL]

Accepted Answer

First, we need to find the amount of energy needed to heat the water from 23.4°C to 98.5°C.
q = mcΔT
q = (35.0 g) (4.184 J/g·°C) (98.5°C - 23.4°C)
q = 11.0 kJ

Next, we need to consider the energy needed to reach the boiling point at this elevation.
ΔHvap = (75.38 J/mol) (18.02 g/mol)
ΔHvap = 1358 J/g
q = (35.0 g) (1.00 g/mL) (1358 J/g)
q = 47.5 kJ

Therefore, the total energy needed is:
qtotal = q1 + q2
qtotal = 11.0 kJ + 47.5 kJ
qtotal = 58.5 kJ

The closest choice is B: 11.0 kJ + 47.5 kJ = 58.5 kJ.

Question 16

Water has a molar heat capacity of 75.38 J/(mol.°C)and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to convert 124 g liquid H₂O at 20.0°C to steam at 100°C?

Accepted Answer

The correct answer is A.Explanation:The energy needed to convert 124 g of liquid H2O at 20.0°C to steam at 100°C can be calculated as follows:1. Calculate the moles of H2O:n = m/M = 124 g / 18.015 g/mol = 6.88 mol2. Calculate the energy needed to raise the temperature of the liquid water from 20.0°C to 100°C:Q1 = n * Cp * ΔT = 6.88 mol * 75.38 J/(mol °C) * (100°C - 20°C) = 39.6 kJ3. Calculate the energy needed to vaporize the water at 100°C:Q2 = n * ΔHvap = 6.88 mol * 40.7 kJ/mol = 282 kJ4. The total energy needed is the sum of Q1 and Q2:Qtotal = Q1 + Q2 = 39.6 kJ + 282 kJ = 322 kJTherefore, the energy needed to convert 124 g of liquid H2O at 20.0°C to steam at 100°C is 322 kJ.

Question 17

A 15 g piece of iron [C_p = 25.09 J/(mol.°C)] is heated to a temperature of 95°C and placed into a bucket containing 4.5 gal of water [c_p = 75.38 J/(mol.°C)] initially at 25°C.Eventually,__________

Accepted Answer

Eventually, the iron and the water will reach thermal equilibrium, meaning they will be at the same temperature.

Question 18

Which of the following statements regarding heat capacity is incorrect?

Accepted Answer

The statement "The molar heat capacity of a substance is an extensive property" is incorrect. Molar heat capacity is an intensive property because it refers to the amount of energy required to raise the temperature of one mole of a substance by 1°C at constant pressure. Extensive properties depend on the size or amount of the substance, while intensive properties do not.

Question 19

How much energy is needed to change the temperature of 25.00 mL of water from 10.0°C to 95.0°C? [C_p = 75.38 J/(mol.°C),d = 1.00 g/mL]

Accepted Answer

To calculate the energy needed, use the formula q = m × C × ΔT. The mass (m) of water is 25.00 g (since density is 1.00 g/mL). The specific heat capacity (C) is 4.184 J/g°C (converted from 75.38 J/mol°C using the molar mass of water, 18.015 g/mol). The temperature change (ΔT) is 85.0°C (95.0°C - 10.0°C). Plugging in these values gives q = 25.00 g × 4.184 J/g°C × 85.0°C = 8,890 J, which is 8.89 kJ.

Question 20

In an experiment,10.0 g of ice at -20.0°C is converted into steam with a temperature of 110.0°C.How much energy is required for this process? [$\Delta$H_vap = 2260 J/g; $\Delta$H_fus = 334 J/g; c_p (ice)= 2.06 J/(g.°C); c_p(water)= 4.18 J/(g.°C); C_p(steam)= 1.99 J/(g.°C)]

Accepted Answer

Explanation:The energy required for this process is the sum of the energy required to melt the ice, the energy required to raise the temperature of the water from 0°C to 100°C, and the energy required to vaporize the water.Energy to melt the ice = 10.0 g * 334 J/g = 3340 JEnergy to raise the temperature of the water = 10.0 g * 4.18 J/(g °C) * (100°C - 0°C) = 4180 JEnergy to vaporize the water = 10.0 g * 2260 J/g = 22600 JTotal energy required = 3340 J + 4180 J + 22600 J = 30120 J = 30.1 kJTherefore, the correct answer is A) 30.7 kJ.

Quiz 9: Thermochemistry-Energy Changes in Chemical Reactions

The heating curve for a substance is shown below.The substance initially is a solid.It then becomes a liquid and a gas.Which of the line segments (I-V) represents the solid to liquid phase transition?

Which of the following statements regarding water and its heat capacity is true?

Find the minimum amount of energy it takes to raise 1.00 pound of lead (454 g) from room temperature (25°C) to its melting point (327°C) and then melt it.The specific heat capacity of lead is 0.159 J/(g.°C) ,the enthalpy of fusion is 24.7 J/g,and the molar mass is 207 g/mol.

How much energy is required to convert 2.785 moles of liquid ammonia at -50.00°C to gas at 25.00°C? [C_p(liquid) = 80.80 J/(mol.°C) ; C_p(gas) = 35.06 J/(mol.°C) ; $\Delta$ H_vap = 23.35 kJ/mol at the normal boiling point of -33.34°C]

How much energy is needed to change the temperature of 275 grams of lead from 10.0°C to 95.0°C? [C_p = 26.7 J/(mol.°C) ]

A 19.5 g piece of titanium [c_p = 0.523 J/(g.°C) ] is heated and then submerged in 1.50 $\times$ 10² grams of water [c_p = 4.18 J/(g.°C) ] initially at 22.7°C.The final temperature comes to 23.7°C.What was the initial temperature of the Ti metal?

The energy content of a Big Mac is 540 Cal.How much water can be heated from 25°C to 95°C by this amount of energy? [d(water) = 1.00 g/mL,c_p (water) = 4.18 J/(g.°C) ,1 Cal = 4.184 kJ]

Given equal masses of the following,which will cool the fastest from the same initial temperature?

What will be the final temperature of a 10.0 g piece of iron [C_p = 25.09 J/(mol.°C) ] initially at 25°C,if it is supplied with 9.5 J from a stove?

Which of the following statements regarding heating curves is incorrect?

A heating curve for some substance is shown below.Which of the line segments (I-V) represents heating of the liquid?

Water has a molar heat capacity of 75.38 J/(mol.°C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to boil 72.0 grams of water at 100°C?

A 1.20 kg piece of granite [c_p = 0.790 J/(g.°C) ] at 60.0°C must be cooled to 24.0°C by submersion in water.How much water [c_p = 4.18 J/(g.°C) ] initially at 18°C would be required?

At a certain elevation,the boiling point of water is 98.5°C.How much energy is needed to heat 35.0 mL of water from 23.4°C to the boiling point at this elevation? [C_p = 75.38 J/(mol.°C) ,d = 1.00 g/mL]

Water has a molar heat capacity of 75.38 J/(mol.°C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to convert 124 g liquid H₂O at 20.0°C to steam at 100°C?

A 15 g piece of iron [C_p = 25.09 J/(mol.°C) ] is heated to a temperature of 95°C and placed into a bucket containing 4.5 gal of water [c_p = 75.38 J/(mol.°C) ] initially at 25°C.Eventually,__________

Which of the following statements regarding heat capacity is incorrect?

How much energy is needed to change the temperature of 25.00 mL of water from 10.0°C to 95.0°C? [C_p = 75.38 J/(mol.°C) ,d = 1.00 g/mL]

In an experiment,10.0 g of ice at -20.0°C is converted into steam with a temperature of 110.0°C.How much energy is required for this process? [ $\Delta$ H_vap = 2260 J/g; $\Delta$ H_fus = 334 J/g; c_p (ice) = 2.06 J/(g.°C) ; c_p(water) = 4.18 J/(g.°C) ; C_p(steam) = 1.99 J/(g.°C) ]

Quiz 9: Thermochemistry-Energy Changes in Chemical Reactions

The heating curve for a substance is shown below.The substance initially is a solid.It then becomes a liquid and a gas.Which of the line segments (I-V) represents the solid to liquid phase transition?

Which of the following statements regarding water and its heat capacity is true?

Find the minimum amount of energy it takes to raise 1.00 pound of lead (454 g) from room temperature (25°C) to its melting point (327°C) and then melt it.The specific heat capacity of lead is 0.159 J/(g . °C) ,the enthalpy of fusion is 24.7 J/g,and the molar mass is 207 g/mol.

How much energy is required to convert 2.785 moles of liquid ammonia at -50.00°C to gas at 25.00°C? [Cp(liquid) = 80.80 J/(mol . °C) ; Cp(gas) = 35.06 J/(mol . °C) ; Δ\DeltaΔ Hvap = 23.35 kJ/mol at the normal boiling point of -33.34°C]

How much energy is needed to change the temperature of 275 grams of lead from 10.0°C to 95.0°C? [Cp = 26.7 J/(mol . °C) ]

A 19.5 g piece of titanium [cp = 0.523 J/(g . °C) ] is heated and then submerged in 1.50 ×\times× 102 grams of water [cp = 4.18 J/(g . °C) ] initially at 22.7°C.The final temperature comes to 23.7°C.What was the initial temperature of the Ti metal?

The energy content of a Big Mac is 540 Cal.How much water can be heated from 25°C to 95°C by this amount of energy? [d(water) = 1.00 g/mL,cp (water) = 4.18 J/(g . °C) ,1 Cal = 4.184 kJ]

Given equal masses of the following,which will cool the fastest from the same initial temperature?

What will be the final temperature of a 10.0 g piece of iron [Cp = 25.09 J/(mol . °C) ] initially at 25°C,if it is supplied with 9.5 J from a stove?

Which of the following statements regarding heating curves is incorrect?

A heating curve for some substance is shown below.Which of the line segments (I-V) represents heating of the liquid?

Water has a molar heat capacity of 75.38 J/(mol . °C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to boil 72.0 grams of water at 100°C?

A 1.20 kg piece of granite [cp = 0.790 J/(g . °C) ] at 60.0°C must be cooled to 24.0°C by submersion in water.How much water [cp = 4.18 J/(g . °C) ] initially at 18°C would be required?

At a certain elevation,the boiling point of water is 98.5°C.How much energy is needed to heat 35.0 mL of water from 23.4°C to the boiling point at this elevation? [Cp = 75.38 J/(mol . °C) ,d = 1.00 g/mL]

Water has a molar heat capacity of 75.38 J/(mol . °C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to convert 124 g liquid H2O at 20.0°C to steam at 100°C?

A 15 g piece of iron [Cp = 25.09 J/(mol . °C) ] is heated to a temperature of 95°C and placed into a bucket containing 4.5 gal of water [cp = 75.38 J/(mol . °C) ] initially at 25°C.Eventually,__________

Which of the following statements regarding heat capacity is incorrect?

How much energy is needed to change the temperature of 25.00 mL of water from 10.0°C to 95.0°C? [Cp = 75.38 J/(mol . °C) ,d = 1.00 g/mL]

In an experiment,10.0 g of ice at -20.0°C is converted into steam with a temperature of 110.0°C.How much energy is required for this process? [ Δ\DeltaΔ Hvap = 2260 J/g; Δ\DeltaΔ Hfus = 334 J/g; cp (ice) = 2.06 J/(g . °C) ; cp(water) = 4.18 J/(g . °C) ; Cp(steam) = 1.99 J/(g . °C) ]

Find the minimum amount of energy it takes to raise 1.00 pound of lead (454 g) from room temperature (25°C) to its melting point (327°C) and then melt it.The specific heat capacity of lead is 0.159 J/(g.°C) ,the enthalpy of fusion is 24.7 J/g,and the molar mass is 207 g/mol.

How much energy is required to convert 2.785 moles of liquid ammonia at -50.00°C to gas at 25.00°C? [C_p(liquid) = 80.80 J/(mol.°C) ; C_p(gas) = 35.06 J/(mol.°C) ; $\Delta$ H_vap = 23.35 kJ/mol at the normal boiling point of -33.34°C]

How much energy is needed to change the temperature of 275 grams of lead from 10.0°C to 95.0°C? [C_p = 26.7 J/(mol.°C) ]

A 19.5 g piece of titanium [c_p = 0.523 J/(g.°C) ] is heated and then submerged in 1.50 $\times$ 10² grams of water [c_p = 4.18 J/(g.°C) ] initially at 22.7°C.The final temperature comes to 23.7°C.What was the initial temperature of the Ti metal?

The energy content of a Big Mac is 540 Cal.How much water can be heated from 25°C to 95°C by this amount of energy? [d(water) = 1.00 g/mL,c_p (water) = 4.18 J/(g.°C) ,1 Cal = 4.184 kJ]

What will be the final temperature of a 10.0 g piece of iron [C_p = 25.09 J/(mol.°C) ] initially at 25°C,if it is supplied with 9.5 J from a stove?

Water has a molar heat capacity of 75.38 J/(mol.°C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to boil 72.0 grams of water at 100°C?

A 1.20 kg piece of granite [c_p = 0.790 J/(g.°C) ] at 60.0°C must be cooled to 24.0°C by submersion in water.How much water [c_p = 4.18 J/(g.°C) ] initially at 18°C would be required?

At a certain elevation,the boiling point of water is 98.5°C.How much energy is needed to heat 35.0 mL of water from 23.4°C to the boiling point at this elevation? [C_p = 75.38 J/(mol.°C) ,d = 1.00 g/mL]

Water has a molar heat capacity of 75.38 J/(mol.°C) and its vaporization enthalpy at 100°C is 40.7 kJ/mol.How much energy is needed to convert 124 g liquid H₂O at 20.0°C to steam at 100°C?

A 15 g piece of iron [C_p = 25.09 J/(mol.°C) ] is heated to a temperature of 95°C and placed into a bucket containing 4.5 gal of water [c_p = 75.38 J/(mol.°C) ] initially at 25°C.Eventually,__________

How much energy is needed to change the temperature of 25.00 mL of water from 10.0°C to 95.0°C? [C_p = 75.38 J/(mol.°C) ,d = 1.00 g/mL]

In an experiment,10.0 g of ice at -20.0°C is converted into steam with a temperature of 110.0°C.How much energy is required for this process? [ $\Delta$ H_vap = 2260 J/g; $\Delta$ H_fus = 334 J/g; c_p (ice) = 2.06 J/(g.°C) ; c_p(water) = 4.18 J/(g.°C) ; C_p(steam) = 1.99 J/(g.°C) ]