General Chemistry
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The vaporization of bromine at 25.0°C is shown below:
Br2(l) → Br2(g)
Find ΔGrxn at 25.0°C when:
i. PBr2 = 1.50 mmHg
ii. PBr2 = 0.150 mmHg
Consider the sublimation of iodine at 25.0 °C:
I2(s) → I2(g)
b. Find ΔGrxn at 25.0 °C under the following nonstandard conditions:
i. PI2 = 1.00 mmHg
ii. PI2 = 0.100 mmHg
Consider the following formation constant for the complexes of a certain metal M:
(1) M(H2O)62+(aq) + 3 en(aq) ⇌ M(en)32+(aq) + 6 H2O(l) Kf,1 = 8.0×1017
(2) M(H2O)62+(aq) + 6 NH3(aq) ⇌ M(NH3)62+(aq) + 6 H2O(l) Kf,2 = 4.0×108
The values indicate that M(NH3)62+ is less stable than M(en)32+. Because both reactions have 6 M−N bonds, the change in enthalpy for the two reactions (ΔH°1 and ΔH°2) should be the same. If ΔH°2 - ΔH°1 is zero, What is the value of ΔS°2 - ΔS°1?
Chromium (III) picolinate, [CrPic3], is a supplement used to treat type II diabetes. It is a source of Cr3+ ions that are shown to increase insulin sensitivity. Even though [Cr(Pic3)] is more efficiently absorbed in the GI tract, its absorption is still quite low. It might be expected that the absorption of Cr3+ will be higher in the stomach because of the following reaction:
[CrPic3](aq) + 3 H3O+(aq) ⇌ Cr3+(aq) + 3 HPic(aq) + 6 H2O(l)
Explain the low absorption of [CrPic3] by predicting the spontaneity of the reaction under standard conditions. (For [Cr(Pic3)], Kf = 3.548×104; for picolinic acid (HPic), Ka = 0.1023)
At 25 ºC, the Ka for HF is 7.2 × 10–4. Determine ΔG at equilibrium.
A 2.00 L vessel is charged with 46.0 g of N2O4 and then heated to 350 K. Calculate the equilibrium molar concentrations of N2O4 and NO2. Use the assumption that ΔHº and ΔSº do not vary with temperature and recall that ΔGº is related with the pressure equilibrium constant.
The reaction A + B → C + D has ΔH°rxn = –158 kJ and ΔS°rxn = 361 J/K. Calculate ΔGº and predict whether the reactants or products are favored at equilibrium at 30 ºC.
For the reaction 2 HgO(s) → 2 Hg(l) + O2(g), use the given thermodynamic data to calculate the equilibrium pressure of O2 in a 1.5 L vessel that contains 10 g of HgO at 350 ºC. Use the assumption that ΔHº and ΔSº do not vary with temperature.
In the reaction, P2(g) is converted into PH3(g): P2(g) + 3 H2(g) → 2 PH3(g). At 298 K, what is the equilibrium constant for the reaction?
ΔG°f, P2 = 103.7 kJ/mol; ΔG°f, H2 = 0; ΔG°f, PH3 = 13.4 kJ/mol
The reaction SO2 (g) + 1/2 O2 (g) ⇌ SO3 is involved in the production of acid rain. The standard free energy of each substance is given below.
ΔG°f, SO2(g) = −300.1 kJ/mol
ΔG°f, O2 (g) = 0
ΔG°f, SO3(g) = −371.1 kJ/mol
What is the equilibrium pressure of SO2 in the system at 298 K when PSO2 = PO2 and PSO2 = 45 torr?
Given the following data
What are the ΔH°, ΔG°, K, and ΔS ° for the reaction Sn (s) + 2 Cl2 (g) → SnCl4 (g) at 25 °C?
Using the following data,
What is the equilibrium pressure of CO2(g) at 450 °C for the reaction?
SrCO3(s) ⇌ SrO(s) + CO2(g)
ΔG°f NaHSO4(s) = −992.8 kJ/mol
ΔG°f NaOH(s) = −379.7 kJ/mol
ΔG°f SO3(g) = −371.1 kJ/mol
What is the Kc expression for the reaction? What are the Kc value and ΔG° value for the reaction at 298 K?
NaHSO4(s) ⇌ NaOH(s) + SO3(g)
The following reaction is spontaneous until some product is formed.
Cl2 (g) + 2 O2 (g) → 2 ClO2 (g)
If 1.0 atm of Cl2 and 1.0 atm of O2 are mixed, what is the maximum partial pressure of ClO2 produced when the reaction stops being spontaneous?
Calculate the partial pressure of CO2 when the decomposition of CaCO3 in an evacuated flask reaches equilibrium at 298K. (Hint: use ΔG°rxn)
CaCO3(s) → CaO (s) + CO2 (g)
What are ΔG° and K for the reaction at 25.00 °C?
SF4 (g) + 2 H2O (l) → SO2 (g) + 4 HF (aq)
Is the reaction spontaneous?
Using ΔG°rxn, what is the equilibrium constant for the reaction at 25°C?
2 SO2(g) + O2(g) → 2 SO3(g)
Calculate the equilibrium constant for the following reaction at 298.15 K.
HCl (g) + NH3 (g) → NH4Cl (s)
For the reaction A(aq) ⇌ 2 B(aq) + C(aq), Kc = 124.6 at 30 ºC. Calculate ΔGrxn at 30 ºC when [A] = 0.32 M, [B] = 0.25 M, and [C] = 0.18 M.
The chemical reaction that takes place at the anode of a Ni-Cd battery is:
Cd(s) + 2 OH−(aq) ⇌ Cd(OH)2(s) + 2 e−
Calculate the value of ΔG for this reaction at −15 °C assuming that the battery is discharged to a point where the hydroxide ion concentration has dropped to 0.025 M (ΔG° = −159.2 kJ/mol).
Formic acid is the simplest carboxylic acid and can be synthesized by the oxidation of formaldehyde:
2 HCHO(g) + O2(g) → 2 HCOOH(l)
What is the value of ΔG for this reaction at 300 K under the following conditions (ΔG° = −518 kJ/mol)? Assume V = 1.00 L.
i) 0.451 mol HCHO, 0.852 mol O2, and 0.150 mol HCOOH
ii) 0.350 mol HCHO, 1.454 mol O2, and 0.950 mol HCOOH
Is the reaction spontaneous under any of these conditions?
Consider the gaseous equilibrium for the dimerization of NO2 at 350 K.
2 NO2(g) ⇌ N2O4(g)
What is the value of ΔG when NO2 = 1.23 atm and N2O4 = 2.45 atm? Use the following ΔG° values:
ΔG° (NO2(g)) = 51.3 kJ/mol
ΔG° (N2O4(g)) = 99.8 kJ/mol
In which direction (forward or reverse) this reaction is spontaneous under the given conditions?
Molecular iodine sublimes at 184 ºC. The standard molar entropies for solid and gaseous iodine are S°I2(s) = 116.1 J/mol K and S°I2(g) = 260.7 J/mol K. Determine the temperature where iodine exhibits a vapor pressure of 430 mmHg.
Nitrogen dioxide (ΔH°f = 33.2 kJ/mol, S° = 240.1 J/mol K) can be prepared by the combustion of nitrogen (S° = 191.6 J/mol K) with oxygen (S° = 205.2 J/mol K). Calculate the equilibrium constants (Kp and Kc) for the formation of NO2 at 500 K. Use the assumption that ΔHº and ΔSº does not vary with temperature.
Heating solid CaCO3 results in the formation of solid CaO and CO2 gas. Calculate ΔGº at 500 K if the total pressure from heating solid CaCO3 in a vacuum container is 1.86 atm.
Using the following thermodynamic data and assuming that ΔH° and ΔS° do not vary with temperature,
For the following reaction, S8 (g) ⇌ 4 S2 (g), what temperature will a mixture containing equal amounts of the two gases be in equilibrium with one another?
The blood plasma contains about 0.137 M Na+ ion concentration, while the intracellular fluid contains about 0.012 M. There is a semi-permeable membrane that separates the plasma from the intracellular fluid. Calculate the ΔG at 37 °C for the transfer of 1.0 mol of Na+ from the blood plasma to the intracellular fluid.
The lactic acid fermentation of glucose produces lactic acid.
C6H12O6 (s) ⇌ 2 C3H6O3 (l)
While the anaerobic fermentation of glucose produces ethanol and carbon dioxide.
C6H12O6 (s) ⇌ 2 C2H5OH (l) + 2 CO2(g)
Make a comparison between the equilibrium constants for the reactions.
(ΔG°f C6H12O6 (s) = -910.4 kJ/mol, ΔG°f C3H6O3 (l) = -711.62 kJ/mol, ΔG°f C2H5OH (l) = -174.8 kJ/mol, ΔG°f CO2(g) = -394.4 kJ/mol)
PN2 = PPH3 = 0.06 atm, PNH3= 0.3 atm, PP4 = 0.2 atm
ΔG°f, P4(g) = 24.4 kJ/mol, ΔG°f, NH3(g) = –16.4, ΔG°f, PH3(g) = 13.5 kJ/mol, ΔG°f, N2(g) = 0
calculate Kp and ΔG at 298 K for the reaction
4 PH3 (g) + 2 N2 (g) ⇌ P4 (g) + 4 NH3 (g)
What is the ΔG at 298 K for the following reaction when the PO2 = 0.78 atm and PO3 = 0.63 atm? (ΔG°f O3 (g) = 163.2 kJ/mol, ΔG°f O2 (g) = 0 kJ/mol)
2 O3 (g) ⇌ 3 O2 (g)
Calculate the ΔG°rxn for the following reaction at 25°C at standard conditions.
H2(g) + Cl2(g) → 2 HCl Kp = 2.39×1033
Given the following decomposition reaction:
P4(g) → 2 P2(g); ΔH°rxn = 229.1 kJ
Calculate the percentage of 0.100 atm P4 that decomposes at 314 K if 47.00% of P4 decomposes to P2 when equilibrium at 298 K is reached.
At 298K, what is the equilibrium constant, K?
ZnS (s) + O2 (g) → Zn(s) + SO2 (g) ΔG°rxn = -101.8 kJ/mol
A hydrated salt has a formula of MSO4•5H2O. At 298 K, the equilibrium vapor pressure of water above the solid is 21.8 mmHg. Calculate the value of ΔG when the vapor pressure of water is 21.8 mmHg and when the vapor pressure of water is 760 mmHg for the following reaction: MSO4•5H2O(s) ⇌ MSO4(s) + 5 H2O(g).
What is ΔH°rxn for a reaction with equilibrium constants of 0.98 at 298 K and 47.9 at 400 K?
Based on the given equilibrium constant at different temperatures, what are ΔS°rxn and ΔH°rxn for the reaction?
2 SO2 (g) + O2 → 2 SO3 (g)
What is ΔG°rxn for the reaction at equilibrium when the temperature is 25°C?
3 F2 (g) + Br2 (l) → 2 BrF3 (g) Kp = 2.47x1080
Consider the reaction of ethylene gas with water vapor to produce ethanol:
C2H4(g) + H2O(g) ⇌ C2H5OH(g)
Determine the ΔGrxn at 25.0°C when PC2H4 = 0.185 atm, PH2O = 0.114 atm, and PC2H5OH = 0.650 atm.
The reaction below represents the decomposition of a generic diatomic molecule in its standard state.
1/2 A2(g) → A(g)
Assuming that the standard molar Gibbs energy of formation of A(g) is 8.12 kJ•mol–1 at 2500 K and –72.20 kJ•mol–1 at 3500 K. Calculate the value of K (thermodynamic equilibrium constant) at each temperature.
Determine the value of ΔH°rxn for these data assuming that ΔH°rxn is independent of temperature.
The standard conditions are 298 K and partial pressure of 1 atm for all species for a gaseous reaction. The standard change in Gibbs free energy is ΔG° = –69.0 kJ/mol for the following reaction:
N2(g) + 3H2(g) ⇌ 2 NH3(g)
Calculate the ΔG for this reaction at 298 K when the partial pressures are: PN2 = 0.360 atm, PH2 = 0.520 atm, and PNH3 = 0.970 atm.
The hydrolysis of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) is an important reaction in the production of energy to do work or drive chemical reactions in biological systems. The reaction is shown below:
ATP(aq) + H2O(l) → ADP(aq) + HPO42–(aq)
for which ΔG°rxn = –30.5 kJ/mol at 37.0°C and pH 7.0. What is the value of ΔGrxn (kJ/mol) in a human erythrocyte in which [ATP] = 2.25 mM, [ADP] = 0.25 mM, and [HPO42–] = 1.65 mM. Is the hydrolysis of ATP spontaneous under these conditions?
Consider the reaction:
I2(g) + Cl2(g) ⇌ 2 ICl(g) Kp = 81.9 at 25 °C
Calculate ΔGrxn for the reaction at 25 °C under the following conditions: PICl = 2.55 atm; PI2 = 0.325 atm; PCl2 = 0.221 atm.