Question 1

If a chemical reaction causes the temperature of the reaction vessel to decrease,it is a(n)__________ reaction.

Accepted Answer

An endothermic reaction is one in which energy is absorbed from the surroundings, causing a decrease in temperature.

Question 2

When solid NH₄NO₃ is dissolved in water,the temperature of the water and beaker gets noticeably colder.The formation of an aqueous solution of ammonium nitrate is __________

Accepted Answer

The noticeable lowering of temperature indicates an absorption of heat from the surroundings to the system, which is a characteristic of an endothermic process.

Question 3

In a steam engine,steam in a cylinder is compressed by a piston exerting 13.5 atm of external pressure.The volume of the cylinder decreases by 20.1 L and simultaneously the steam heats up.If the total energy change of the steam is 32.8 kJ,calculate the heat flow into/out of the steam.(101.3 J = 1 L.atm)

Accepted Answer

The answer of In a steam engine,steam in a cylinder...

Question 4

Which of the following reactions would you predict is endothermic?

Accepted Answer

In this reaction, the products have more bonds than the reactants, which indicates that energy has been absorbed. This means that the reaction is endothermic.

Question 5

The reaction of sulfur dioxide gas with oxygen to form sulfur trioxide gas at 25°C and 1 atm releases approximately 198.5 kJ of heat while absorbing approximately 2.5 kJ of work.Which of the following is true? 2 SO₂(g)+ O₂(g)$\to$ 2 SO₃(g)

Accepted Answer

The reaction is exothermic as it releases heat. The enthalpy change (ΔH) is the heat released, which is -198.5 kJ. The internal energy change (ΔE) is ΔH minus the work done on the system, so ΔE is less negative than ΔH.

Question 6

Enthalpy change is defined as __________

Accepted Answer

Enthalpy change is defined as the energy that is transferred into or out of a system when the pressure is constant and only P-V work is done. This can be expressed mathematically as ΔH = ΔU + PΔV, where ΔU is the change in internal energy, P is the pressure, and ΔV is the change in volume.

Question 7

When one mole of zinc and two moles of hydrochloric acid undergo the reaction Zn(s)+ 2 HCl(aq)$\to$ZnCl₂(aq)+ H₂(g),150.0 kJ of thermal energy are released at 25.00°C and 1.000 atm.The H₂ gas generated does approximately 2.500 kJ of work on the surroundings as it expands.Calculate $\Delta$E for the reaction (assume only P-V work is done).

Accepted Answer

The answer of When one mole of zinc and two...

Question 8

When solid sodium hydroxide (NaOH)pellets are dissolved in water,the temperature of the water and beaker rises.The formation of an aqueous solution of sodium hydroxide is __________

Accepted Answer

The fact that the temperature of the water and beaker rises indicates that the dissolution of solid sodium hydroxide in water releases energy, which is characteristic of an exothermic process.

Question 9

A cup of coffee is heated in a microwave oven.It absorbs 40 kJ of energy from the microwave,and the volume slightly increases.Which one of the following statements correctly describes the relationship between the change in enthalpy $\Delta$H and the change in internal energy $\Delta$E of the coffee?

Accepted Answer

The change in enthalpy (ΔH) is equal to the amount of heat absorbed or released in a process at a constant pressure, while the change in internal energy (ΔE) is equal to the amount of heat absorbed or released in a process at a constant volume. In this case, the cup of coffee absorbs 40 kJ of energy from the microwave, which corresponds to the change in enthalpy of the system. However, since the volume of the coffee slightly increases, it means that some of the absorbed energy is used to do work against the external pressure (i.e. atmospheric pressure), which is equivalent to the change in internal energy. Therefore, the change in internal energy is less than 40 kJ, so we can conclude that:

ΔH = 40 kJ 
ΔE < 40 kJ

The only choice that reflects this relationship is A.

Question 10

The volume change associated with a chemical reaction is often approximated as being directly proportional to the change in the number of moles of gas (moles of gaseous products - moles of gaseous reactants).The combustion of methanol at 25°C and 1 atm releases about 1453 kJ of heat.Which of the following correctly describes the relationship between vE and $\Delta$H? 2 CH₃OH( )+ 3 O₂(g)$\to$ 2 CO₂(g)+ 4 H₂O( )

Accepted Answer

The answer of The volume change associated with a chemical...

Question 11

Solid calcium carbonate is heated to produce solid calcium oxide and carbon dioxide gas in a cylinder fitted with a movable piston.The CO₂ gas generated does 8650 J of expansion work under a constant pressure of 0.772 atm.What is the volume change experienced by the gas? (101.3 J = 1 L.atm)

Accepted Answer

The answer of Solid calcium carbonate is heated to produce...

Question 12

During an exothermic process,__________ for the system.

Accepted Answer

The answer of During an exothermic process,__________ for the system.
...

Question 13

In a steam engine,steam in a cylinder returns to its original state after an expansion/compression cycle.In the expansion step,the volume of the steam increases by exactly 12 L at a constant pressure of exactly 10 atm while 6228 J of heat flows in.In the compression step,the volume of the gas decreases by exactly 12 L at a constant pressure of exactly 15 atm.Calculate the heat flow into/out of the steam in the second step.(101.3 J = 1 L . atm)

Accepted Answer

The work done on the steam during compression is calculated using W = PΔV. Here, P = 15 atm and ΔV = -12 L. Converting to joules: W = 15 atm * (-12 L) * 101.3 J/L atm = -18,234 J. Since the internal energy change over the full cycle is zero, the heat flow Q = -W = 18,234 J. Thus, the heat flow into the steam is -12,310 J.

Question 14

The reaction of nitrogen with oxygen to form nitrogen dioxide gas at 25°C and 1 atm requires approximately 66.4 kJ of thermal energy.The change in internal energy is about 68.9 kJ.Which of the following is true? 2 N₂(g)+ O₂(g)$\to$ 2 NO₂(g)

Accepted Answer

The answer of The reaction of nitrogen with oxygen to...

Question 15

Calculate the work performed on/by a gas when it is compressed under a constant pressure of 8.00 atm from 95.0 L to 9.5 L.(101.3 J = 1 L.atm)

Accepted Answer

The answer of Calculate the work performed on/by a gas...

Question 16

If a chemical reaction causes the temperature of the reaction vessel to increase,it is a(n)__________ reaction.

Accepted Answer

An increase in temperature indicates that heat energy is being released from the reaction, which means the reaction is exothermic. Endothermic reactions absorb heat energy and would cause a decrease in temperature. Spontaneous, fast, and slow do not indicate the direction of heat flow in the reaction.

Question 17

When trinitrotoluene (TNT)detonates according to the reaction 2 C₇H₅N₃O₆(s)$\to$3 N₂(g)+ 5 H₂(g)+ 12 CO(g)+ 2 C(s),the enthalpy change at 25°C and 1 atm is -1475 kJ while the volume increases by about 489 L.What is the internal energy change (assume only P-V work is done)?

Accepted Answer

The answer of When trinitrotoluene (TNT)detonates according to the reaction...

Question 18

How much work does a gas do when it expands against a constant pressure of 0.500 atm from a volume of 50.00 mL to a volume of 350.00 mL? (101.3 J = 1 L.atm)

Accepted Answer

The answer of How much work does a gas do...

Question 19

In a steam engine,steam in a cylinder expands against a piston exerting 10.00 atm of external pressure.The volume of the cylinder increases by 10.00 L and simultaneously the steam cools,losing 3.000 $\times$10³ kJ of energy to the surroundings.What is the change in energy of the steam? (101.3 J = 1 L.atm)

Accepted Answer

We can use the first law of thermodynamics to solve this problem:
ΔE = Q - W
where ΔE is the change in energy of the system, Q is the heat transferred to or from the system, and W is the work done by or on the system.
Since the volume of the cylinder increases and the external pressure is constant, the work done by the system is:
W = -PextΔV = -(10.00 atm) * (10.00 L) = -100.0 L*atm = -100.0 J
Note that we had to convert the units of L*atm to J using the conversion factor given in the problem.
The heat transferred to the surroundings is given as Q = -3.000 kJ.
Therefore, the change in energy of the steam is:
ΔE = Q - W = (-3.000 kJ) - (-100.0 J) = -3.010 kJ
Since we were asked for the answer in kJ, we can choose option (A) as the correct answer.

Question 20

A container of water is heated with 10 J of energy at constant pressure.What is the enthalpy change ($\Delta$H)for this process?

Accepted Answer

Enthalpy change (ΔH) is the heat absorbed or released by a system under constant pressure. In this case, water is heated with 10 J of energy at constant pressure. Therefore, the enthalpy change (ΔH) will be equal to the amount of heat added, which is +10 J. Hence, the correct answer is C.

Quiz 9: Thermochemistry-Energy Changes in Chemical Reactions

If a chemical reaction causes the temperature of the reaction vessel to decrease,it is a(n) __________ reaction.

When solid NH₄NO₃ is dissolved in water,the temperature of the water and beaker gets noticeably colder.The formation of an aqueous solution of ammonium nitrate is __________

Which of the following reactions would you predict is endothermic?

The reaction of sulfur dioxide gas with oxygen to form sulfur trioxide gas at 25°C and 1 atm releases approximately 198.5 kJ of heat while absorbing approximately 2.5 kJ of work.Which of the following is true? 2 SO₂(g) + O₂(g) $\to$ 2 SO₃(g)

Enthalpy change is defined as __________

When solid sodium hydroxide (NaOH) pellets are dissolved in water,the temperature of the water and beaker rises.The formation of an aqueous solution of sodium hydroxide is __________

Solid calcium carbonate is heated to produce solid calcium oxide and carbon dioxide gas in a cylinder fitted with a movable piston.The CO₂ gas generated does 8650 J of expansion work under a constant pressure of 0.772 atm.What is the volume change experienced by the gas? (101.3 J = 1 L.atm)

During an exothermic process,__________ for the system.

The reaction of nitrogen with oxygen to form nitrogen dioxide gas at 25°C and 1 atm requires approximately 66.4 kJ of thermal energy.The change in internal energy is about 68.9 kJ.Which of the following is true? 2 N₂(g) + O₂(g) $\to$ 2 NO₂(g)

Calculate the work performed on/by a gas when it is compressed under a constant pressure of 8.00 atm from 95.0 L to 9.5 L.(101.3 J = 1 L.atm)

If a chemical reaction causes the temperature of the reaction vessel to increase,it is a(n) __________ reaction.

When trinitrotoluene (TNT) detonates according to the reaction 2 C₇H₅N₃O₆(s) $\to$ 3 N₂(g) + 5 H₂(g) + 12 CO(g) + 2 C(s) ,the enthalpy change at 25°C and 1 atm is -1475 kJ while the volume increases by about 489 L.What is the internal energy change (assume only P-V work is done) ?

How much work does a gas do when it expands against a constant pressure of 0.500 atm from a volume of 50.00 mL to a volume of 350.00 mL? (101.3 J = 1 L.atm)

A container of water is heated with 10 J of energy at constant pressure.What is the enthalpy change ( $\Delta$ H) for this process?

Quiz 9: Thermochemistry-Energy Changes in Chemical Reactions

If a chemical reaction causes the temperature of the reaction vessel to decrease,it is a(n) __________ reaction.

When solid NH4NO3 is dissolved in water,the temperature of the water and beaker gets noticeably colder.The formation of an aqueous solution of ammonium nitrate is __________

Which of the following reactions would you predict is endothermic?

The reaction of sulfur dioxide gas with oxygen to form sulfur trioxide gas at 25°C and 1 atm releases approximately 198.5 kJ of heat while absorbing approximately 2.5 kJ of work.Which of the following is true? 2 SO2(g) + O2(g) →\to→ 2 SO3(g)

Enthalpy change is defined as __________

When solid sodium hydroxide (NaOH) pellets are dissolved in water,the temperature of the water and beaker rises.The formation of an aqueous solution of sodium hydroxide is __________

Solid calcium carbonate is heated to produce solid calcium oxide and carbon dioxide gas in a cylinder fitted with a movable piston.The CO2 gas generated does 8650 J of expansion work under a constant pressure of 0.772 atm.What is the volume change experienced by the gas? (101.3 J = 1 L . atm)

During an exothermic process,__________ for the system.

The reaction of nitrogen with oxygen to form nitrogen dioxide gas at 25°C and 1 atm requires approximately 66.4 kJ of thermal energy.The change in internal energy is about 68.9 kJ.Which of the following is true? 2 N2(g) + O2(g) →\to→ 2 NO2(g)

Calculate the work performed on/by a gas when it is compressed under a constant pressure of 8.00 atm from 95.0 L to 9.5 L.(101.3 J = 1 L . atm)

If a chemical reaction causes the temperature of the reaction vessel to increase,it is a(n) __________ reaction.

When trinitrotoluene (TNT) detonates according to the reaction 2 C7H5N3O6(s) →\to→ 3 N2(g) + 5 H2(g) + 12 CO(g) + 2 C(s) ,the enthalpy change at 25°C and 1 atm is -1475 kJ while the volume increases by about 489 L.What is the internal energy change (assume only P-V work is done) ?

How much work does a gas do when it expands against a constant pressure of 0.500 atm from a volume of 50.00 mL to a volume of 350.00 mL? (101.3 J = 1 L . atm)

A container of water is heated with 10 J of energy at constant pressure.What is the enthalpy change ( Δ\DeltaΔ H) for this process?

When solid NH₄NO₃ is dissolved in water,the temperature of the water and beaker gets noticeably colder.The formation of an aqueous solution of ammonium nitrate is __________

The reaction of sulfur dioxide gas with oxygen to form sulfur trioxide gas at 25°C and 1 atm releases approximately 198.5 kJ of heat while absorbing approximately 2.5 kJ of work.Which of the following is true? 2 SO₂(g) + O₂(g) $\to$ 2 SO₃(g)

Solid calcium carbonate is heated to produce solid calcium oxide and carbon dioxide gas in a cylinder fitted with a movable piston.The CO₂ gas generated does 8650 J of expansion work under a constant pressure of 0.772 atm.What is the volume change experienced by the gas? (101.3 J = 1 L.atm)

The reaction of nitrogen with oxygen to form nitrogen dioxide gas at 25°C and 1 atm requires approximately 66.4 kJ of thermal energy.The change in internal energy is about 68.9 kJ.Which of the following is true? 2 N₂(g) + O₂(g) $\to$ 2 NO₂(g)

Calculate the work performed on/by a gas when it is compressed under a constant pressure of 8.00 atm from 95.0 L to 9.5 L.(101.3 J = 1 L.atm)

When trinitrotoluene (TNT) detonates according to the reaction 2 C₇H₅N₃O₆(s) $\to$ 3 N₂(g) + 5 H₂(g) + 12 CO(g) + 2 C(s) ,the enthalpy change at 25°C and 1 atm is -1475 kJ while the volume increases by about 489 L.What is the internal energy change (assume only P-V work is done) ?

How much work does a gas do when it expands against a constant pressure of 0.500 atm from a volume of 50.00 mL to a volume of 350.00 mL? (101.3 J = 1 L.atm)

A container of water is heated with 10 J of energy at constant pressure.What is the enthalpy change ( $\Delta$ H) for this process?