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Exam 8: Thermochemistry: Chemical Energy

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Question 1

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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.C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(l) III.H₂(g) + Cl₂(g) → 2 HCl(g) IV.N₂O₄(g) → 2 NO₂(g)

A) I)
B) III.
C) IV.
D) II.and IV.

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Question 2

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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) w = + and ΔH = +
B) w = + and ΔH = -
C) w = - and ΔH = +
D) w = - and ΔH = -

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Question 3

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Which is the most exothermic reaction?

It takes 11.2 kJ of energy to raise the temperature of 145 g of benzene from 23.0°C to 68.0°C.What is the specific heat of benzene?

Is thermal energy a form of kinetic or potential molecular energy?

Find ΔE° for the reaction below if the process is carried out at a constant pressure of 1.00 atm and ΔV (the volume change) = -24.5 L.(1 L ∙ atm = 101 J) 2 CO(g) + O₂ (g) → 2 CO₂(g) ΔH° = -566.kJ

The sign of ΔG for a reaction is if the reaction is spontaneous,________ if the reaction is at equilibrium,and ________ if the reaction is nonspontaneous.

When heated,mercury(II) oxide decomposes into elemental mercury and oxygen: 2 HgO(s) → 2 Hg(l) + O₂(g) ΔH° = 181.6 kJ ΔS° = 216.4 J/K Estimate the temperature at which HgO should begin to decompose if the partial pressure of O₂(g) is constant at 1.00 atm.

For a particular process that is carried out at constant pressure,q = 145 kJ and w = - 35 kJ.Therefore,

A reaction is performed in a 1-L balloon at 25°C and 1 atm pressure.At the end of the reaction the balloon has expanded to 1.5 L and the surface of the balloon has a temperature of 35°C and is at 1 atm pressure.Determine whether the signs of the heat transferred,the work,and the energy change,respectively,are positive or negative.

Given that ΔH°= -311 kJ for the hydrogenation of acetylene,C₂H₂: H-C=C-H(g) + 2 H₂(g) → CH₃-CH₃(g) And the following bond dissociation energies,estimate a value for the C-to-C triple bond dissociation energy.

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

For the conversion of water to ice at 25°C and 1 atm,

At 1 atm pressure the heat of sublimation of gallium is 277 kJ/mol and the heat of vaporization is 271 kJ/mol.How much heat is required to melt 1.50 mol of gallium at 1 atm pressure?

For a process at constant pressure,49,600 calories of heat are released.This quantity of heat is equivalent to

What is the thermodynamic criterion for equilibrium for a reaction at constant temperature and pressure (PV work only) ?

When 2.000 moles of H₂(g) reacts with 1.000 mol of O₂(g) to form 2.000 mol of H₂O(l) at 25°C and a constant pressure of 1.00 atm.If 136.6 kJ of heat are released during this reaction,and PΔV is equal to -7.400 kJ,then

-The reaction represented in the above drawing is likely to be

Which combination always results in a reaction being spontaneous?

When 0.455 g of anthracene,C₁₄H₁₀,is combusted in a bomb calorimeter that has a water jacket containing 500.g of water,the temperature of the water increases by 8.63°C.Assuming that the specific heat of water is 4.18 J/(g ∙ °C) ,and that the heat absorption by the calorimeter is negligible,estimate the enthalpy of combustion per mole of anthracene.