Ch.7 - Thermochemistry

Tro - Chemistry: A Molecular Approach 5th Edition

Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371당신이 사용하는 게 아니라요?교과서 변경

Tro 5th Edition

Ch.7 - Thermochemistry

문제 75b

7장, 문제 75b

Determine whether each process is exothermic or endothermic and indicate the sign of ΔH. a. natural gas burning on a stove b. isopropyl alcohol evaporating from skin c. water condensing from steam Indicate the sign of ΔH for the following processes.

검증된 단계별 안내

Identify the type of process for each scenario: exothermic or endothermic.

For an exothermic process, energy is released to the surroundings, and the sign of \( \Delta H \) is negative.

For an endothermic process, energy is absorbed from the surroundings, and the sign of \( \Delta H \) is positive.

a. Natural gas burning on a stove is a combustion reaction, which is exothermic, so \( \Delta H \) is negative.

b. Isopropyl alcohol evaporating from skin is an endothermic process, as it requires energy to change from liquid to gas, so \( \Delta H \) is positive.

c. Water condensing from steam is an exothermic process, as it releases energy when changing from gas to liquid, so \( \Delta H \) is negative.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

도움이 되었나요?

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Exothermic and Endothermic Processes

Exothermic processes release energy, usually in the form of heat, to the surroundings, resulting in a negative change in enthalpy (ΔH < 0). In contrast, endothermic processes absorb energy from the surroundings, leading to a positive change in enthalpy (ΔH > 0). Understanding these definitions is crucial for determining the nature of the processes described in the question.

Enthalpy (ΔH)

Enthalpy (ΔH) is a thermodynamic quantity that represents the total heat content of a system. It is used to quantify the energy change during a chemical reaction or physical process. The sign of ΔH indicates whether the process is exothermic (negative ΔH) or endothermic (positive ΔH), which is essential for analyzing the processes mentioned in the question.

Phase Changes and Energy Transfer

Phase changes, such as evaporation and condensation, involve energy transfer that affects the temperature and state of a substance. For example, evaporation is an endothermic process as it requires energy to convert liquid to gas, while condensation is exothermic as it releases energy when gas turns into liquid. Recognizing these phase changes helps in determining the sign of ΔH for the processes listed.

관련 실천

교과서 질문

When 0.514 g of biphenyl (C₁₂H₁₀) undergoes combustion in a bomb calorimeter, the temperature rises from 25.8 °C to 29.4 °C. Find ΔE_rxn for the combustion of biphenyl in kJ/mol biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/°C.

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

a. A + B → 2 C ΔH₁

2 C→ A + B ΔH₂ = ?

339

views

교과서 질문

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

b. A + 1/2 B → C ΔH₁

2 A + B → 2 C ΔH₂ = ?

1909

views

교과서 질문

Zinc metal reacts with hydrochloric acid according to the balanced equation: Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g) When 0.103 g of Zn(s) is combined with enough HCl to make 50.0 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 22.5 °C to 23.7 °C. Find ΔH_rxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

27264

views

교과서 질문

Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the endothermic reaction: NH₄NO₃(s) → NH₄⁺(aq) + NO₃^– (aq) In order to measure the enthalpy change for this reaction, 1.25 g of NH₄NO₃ is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 °C and the final temperature (after the solid dissolves) is 21.9 °C. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

3188

views

comments