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Exam 9: Thermochemistry: Chemical Energy

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Question 51

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One method for making ethanol,C₂H₅OH,involves the gas-phase hydration of ethylene,C₂H₄: Estimate ΔH for this reaction from the given average bond dissociation energies,D.

A) -580 kJ
B) -35 kJ
C) +35 kJ
D) 580 kJ

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Question 52

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For the freezing of liquid hexane,C₆H_,at a given temperature and pressure,

A) ΔH is negative and ΔS is negative.
B) ΔH is negative and ΔS is positive.
C) ΔH is positive and ΔS is negative.
D) ΔH is positive and ΔS is positive.

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Question 53

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Imagine a reaction that results in a change in both volume and temperature,as shown in the diagram below.What is the sign of the work being done and the sign of the enthalpy change involved in this reaction?

A property whose value depends only on the present condition of the system and not how the system arrived at that condition is called a ________ function.

Acetylene torches utilize the following reaction: 2 C₂H₂(g) + 5 O₂(g) → 4 CO₂(g) + 2 H₂O(g) Use the given standard enthalpies of formation to calculate ΔH° for this reaction.

The sum of the potential and kinetic energies for every molecule or ion in a system is the ________ energy of the system and is given the symbol ________.

Coal gasification can be represented by the equation: 2 C(s) + 2 H₂O(g) → CH₄(g) + CO₂(g) ΔH = ? Use the following information to find ΔH for the reaction above. CO(g) + H₂(g) → C(s) + H₂O(g) ΔH = -131 kJ CO(g) + H₂O(g) → CO₂(g) + H₂(g) ΔH = -41 kJ CO(g) + 3 H₂(g) → CH₄(g) + H₂O(g) ΔH = -206 kJ

At constant pressure for which of the reactions shown below should ΔH° be greater than ΔE°? I.2 SO₂(g) + O₂(g) → 2 SO₃(g) II.C₉H₂₀(g) + 14 O₂(g) → 9 CO₂(g) + 10 H₂O(l) III.H₂(g) + F₂(g) → 2 HF(g) IV.N₂O₄(g) → 2 NO₂(g)

For a process at constant pressure,

The law of conservation of energy is also known as the ________ law of thermodynamics.

Which is not a spontaneous process?

For a process at constant volume,

At constant pressure,the combustion of 30.00 g of C₂H₆(g) releases 1560 kJ of heat.What is ΔH for the reaction given below? 2 C₂H₆(g) + 7 O₂(g) → 4 CO₂(g) + 6 H₂O(l)

For the reaction 2CH₄ (g) + 3 Cl₂ (g) → 2 CHCl₃ (l) + 3 H₂ (g) ,ΔH° = -118.6 kJ. ΔH°_f = -134.1 kJ/mol for CHCl₃ (l) .Find ΔH°_f for CH₄ (g) .

Calculate the total quantity of heat required to convert 50.0 g of liquid CCl₄(l) from 25.0°C to gaseous CCl₄ at 76.8°C (the normal boiling point for CCl₄) ? The specific heat of CCl₄(l) is 0.857 J/(g ∙ °C) ,its heat of fusion is and its heat of vaporization is

A gas absorbs 0.0 J of heat and then performs 13.1 J of work.The change in internal energy of the gas is

For most chemical reactions

When 2.500 mol of CH₄(g) reacts with excess Cl₂(g) at constant pressure according to the chemical equation shown below,1770.kJ of heat are released.Calculate the value of ΔH for this reaction,as written. 2 CH₄(g) + 3 Cl₂(g) → 2 CHCl₃(l) + 3 H₂(g) ΔH = ?

For a particular process that is carried out at constant pressure,q = 140 kJ and w = -30 kJ.Therefore,

What is expected when the reaction shown below takes place in a thermally-insulated container outfitted with a movable piston at a constant atmospheric pressure of 1 atm? 2 C₂H₆(g) + 7 O₂(g) → 4 CO₂(g) + 6 H₂O(g)