Mastering Chemistry - Ch. 5

Calculate ΔH for the reaction:NO (g) + O (g) → NO2 (g)given the following information:

-304.1 kJ

Given: C2H4(g)+3O2(g)↔2CO2(g)+2H2O(g) ΔHf(C2H4)=52.5kJ/mol ΔHf(H2O)=-285.8 kJ/mol Δ H0rxn=-1411.1 kJ/mol. Find ΔHf(CO2)=.

-393.5 kJ/mol

Calculate ΔH (in kJ/mol NaOH) for the solution process NaOH(s)→Na+(aq)+OH−(aq)Assume that the specific heat of the solution is the same as that of pure water.

-44.4 kJ/mol

From the enthalpies of reaction calculate ΔH for the reaction CO(g)+2H2(g) → CH3OH(g)

-90.7 kJ

A 100.0-g bar of gold is heated from 25 ∘C to 50 ∘C, during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant. Based on the data, calculate the specific heat of Au(s).

0.13 J/g ∘C

What is the specific heat of silver?

0.235 J⋅(g⋅∘C)−1

What is the molar heat capacity of Au(s)?

25 J⋅(mol⋅∘C)−1

Calculate ΔH (in kJ/mol NH4NO3) for the solution process NH4NO3(s)→NH+4(aq)+NO−3(aq) Assume that the specific heat of the solution is the same as that of pure water.

26 kJ/mol

What is ΔH∘rxnΔHrxn∘ for the following chemical reaction? CO(g)+NH3(g)→HCN(g)+H2O(g) You can use the following table of standard heats of formation (ΔH∘f)(ΔHf∘) to calculate the enthalpy of the given reaction.

45.1 kJ

For the reaction given in Part A, how much heat is absorbed when 3.80 mol of A reacts?

530 kJ

How much heat is needed to raise the temperature of a 5.0 gram block of aluminum from 22.0° C to 37.0° C?

68 J

The specific heat of silver (Ag) is 0.245 J/ºC g. Determine the energy required to raise the temperature of 350. g of Ag from 293 K to 400 K.

9.17 kJ

The equations given in the problem introduction can be added together to give the following reaction: overall: C + 1/2O2→CO However, one of them must be reversed. Which one?

CO+12O2→CO2

It takes 54.0 J to raise the temperature of an 10.7 g piece of unknown metal from 13.0∘C to 24.3 ∘C. What is the specific heat for the metal?

Cs=0.447 J⋅(g⋅∘C)−1

Which substance in the table undergoes the greatest temperature change when the same mass of each substance absorbs the same quantity of heat?

Hg(l)

What are the units of specific heat?

J/g−K or J/g−∘C.

What are the units of molar heat capacity?

J/mol−KJ or J/mol−∘C

For which of the following reactions is ΔHrxn∘ equal to ΔHf∘ of the product(s)?You do not need to look up any values to answer this question.

Li(s)+12F2(g)→LiF(s) S(s)+O2(g)→SO2(g)

Write a balanced chemical equation for the reaction depicted.

O2(g)+N2(g)→2NO(g)

Enthalpy diagram for combustion of 1 mol of methane. The enthalpy change of the one-step reaction equals the sum of the enthalpy changes of the reaction run in two steps: -890 kJ = -802 kJ+ (-88 kJ). What process corresponds to the -88 kJ enthalpy change?

The condensation of 2 H2O(g) to 2 H2O(l).

Suppose that the same amount of heat is added to two 10.0-g blocks of metal, both initially at the same temperature. One block is gold metal, and one is iron metal. Which block will have the greater rise in temperature after the addition of the heat? (Note that the specific heat of iron is 0.451 J/g⋅∘C.)

The gold block will have the higher final temperature.

Choose the enthalpy diagram for the reaction. (Asume the bold arrow shows the reaction as written; combination of the two thin arrows shows an alternate route from A to B).

Two arrows up to B, one arrow down from A

The overall enthalpy change for a reaction _____.

depends only on the amount of matter that undergoes the change and on the initial state of the reactants and the final state of the products

Is the process shown in the figure endothermic or exothermic?

endothermic

Is this process endothermic or exothermic?

endothermic

ΔH f° _____.

is usually reported at 298K

If you know the specific heat of copper, what additional information do you need to calculate the heat capacity of a particular piece of copper pipe?

mass of the piece

A volume of 110. mL of H2O is initially at room temperature (22.00 ∘C). A chilled steel rod at 2.00 ∘C is placed in the water. If the final temperature of the system is 21.20 ∘C , what is the mass of the steel bar? Use the following values: specific heat of water = 4.18 J/(g⋅∘C) specific heat of steel = 0.452 J/(g⋅∘C)

mass of the steel =42.4 g

The specific heat of water is 4.18 J/(g⋅∘C). Calculate the molar heat capacity of water.

molar heat capacity for water=75.2 J/mol⋅∘C

The molar heat capacity of silver is 25.35 J/mol⋅∘C. How much energy would it take to raise the temperature of 10.7 g of silver by 12.1 ∘C?

q =30.4 J

Combustion reactions are most conveniently studied _____.

using constant-volume calorimetry

Predict whether w is positive, negative, or zero.

zero

Consider the reaction C12H22O11(s)+12O2(g)→12CO2(g)+11H2O(l) in which 10.0 g of sucrose, C12H22O11, was burned in a bomb calorimeter with a heat capacity of 7.50 kJ/∘C. The temperature increase inside the calorimeter was found to be 22.0 ∘C. Calculate the change in internal energy, ΔE, for this reaction per mole of sucrose.

Δ =-5650kJ/mol

Given the following data: use Hess's law to calculate ΔH for the following reaction: N2O(g)+NO2(g)→3NO(g)

ΔH =155.7kJ

What is the enthalpy for reaction 1 reversed? reaction 1 reversed: CO2→CO + 1/2O2

ΔH =283kJ/mol

Consider the following hypothetical reactions: A→BΔH=+24kJ B→CΔH=+62kJ Use Hess's law to calculate the enthalpy change for the reaction A→C.

ΔH =86kJ

Using data from Appendix C in the textbook, determine ΔH for the formation of one mole of the product.

ΔH =90.4kJ

A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 173 g of solution. The reaction caused the temperature of the solution to rise from 21.00 to 24.70 ∘C. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water.

ΔH=-1.34kJ/mol

What is the enthalpy for the following reaction? overall: C + 1/2O2→CO

ΔH=-110kJ/mol

A calorimeter contains 31.0 mL of water at 15.0 ∘C . When 2.00 g of X (a substance with a molar mass of 53.0 g/mol ) is added, it dissolves via the reaction X(s)+H2O(l)→X(aq) and the temperature of the solution increases to 26.5 ∘C . Calculate the enthalpy change, ΔH, for this reaction per mole of X. Assume that the specific heat of the resulting solution is equal to that of water [4.18 J/(g⋅∘C)], that density of water is 1.00 g/mL, and that no heat is lost to the calorimeter itself, nor to the surroundings.

ΔH=-42.0kJ/mol

From the enthalpies of reaction calculate ΔH for the reaction of ethylene withF2:C2H4(g)+6F2(g)→2CF4(g)+4HF(g)

ΔHrxn=-2490kJ

Calculate the standard enthalpy change for the reaction 2A+B⇌2C+2D

ΔHrxn∘ =279 kJ

Calculate the enthalpy change for the reaction P4O6(s)+2O2(g)→P4O10(s) given the following enthalpies of reaction: P4(s)+3O2(g)→P4O6(s)ΔH=−1640.1kJ P4(s)+5O2(g)→P4O10(s)ΔH=−2940.1kJ

ΔHrxn∘=-1300kJ

The combustion of propane, C3H8C3H8, occurs via the reaction C3H8(g)+5O2(g)→3CO2(g)+4H2O(g)with heat of formation values given by the following table: SubstanceΔH∘fΔHf∘(kJ/mol)C3H8C3H8(g)-104.7 CO2(g)−393.5 H2O(g)−−241.8

ΔHrxn∘=-2043 kJ

Calculate the enthalpy of the reaction 2NO(g)+O2(g)→2NO2(g) given the following reactions and enthalpies of formation:

ΔH∘ =-114.0 kJ

Calculate the enthalpy of the reaction 4B(s)+3O2(g)→2B2O3(s) given the following pertinent information:

ΔH∘ =-2552 kJ

Suppose the overall reaction is endothermic. What can you conclude?

ΔH∘f(A)<ΔH∘f(B)