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24 solutions

Hess's Law

Q. In the following overall chemical reaction, aluminum displaces chromium from chromium(III) oxide and forms aluminum oxide. 2 Al(s) + Cr2O3(s) -> 2 Cr(s) + Al2O3(s); ΔH = ? Find the change in enthalpy for this reaction, using Hess' law and the enthalpy changes for the reactions given below. (1a) 4 Al(s) + 3 O2(g) -> 2 Al2O3(s); ΔH = -3351.4 kJ (2a) 4 Cr(s) + 3 O2(g) -> 2 Cr2O3(s); ΔH = -2279.4 kJ

Solved • Jul 18, 2019

Hess's Law

Q. The enthalpies of reaction for a set of reaction steps are as follows. ΔH1 = 408 kJ ΔH2 = 111 kJ ΔH3 = -947 kJ ΔH4 = -40.8 kJ If adding the chemical equations according to the expression below can produce the overall chemical equation, what is the overall enthalpy change for the reaction? (Include the sign of the value in your answer.) Overall equation = Equation 1 + Equation 2 + Equation 3 + Equation 4

Solved • Jul 18, 2019

Hess's Law

Q. The following sequence of reactions occurs in the commercial production of aqueous nitric acid. (The overall industrial process produces excess NO.) 4 NH3(g) + 5 02(g) -> 4 NO(g) + 6 H20(/) AH = -1166.0 kJ/mol (1) 2 NO(g) + 02(g) -> 2 NO2(g)AH = -116.2 kJ/mol (2) 3 NO2(g) + H20(/) -> 2 HNO3(aq) + NO(g) OH = -137.3 kJ/mol (3) Determine the total energy change (in kJ) for the production of one mole of aqueous nitric acid by this proces

Solved • Jul 18, 2019

Hess's Law

Q. Calculate iH (in kJ) for the process Hg2Br2(s) —' 2 Hg(/) + Br2(/) from the following information. Hg(/) + Br2(/) —> HgBr2(s) AH2980 = —170.7 IdHg(/) + HgBr2(s) —> Hg2Br2(s)01-/2980 = —36.2 kJ

Solved • Jul 18, 2019

Hess's Law

Q. Calculate AH2.980 (in kJ) for the process P(s) + 5/2 Cl2(g) -> PCI5(g) from the following information. P(s) + 3/2 Cl2(g) -> PCI3(g) AH2980 0 = -287 kJPCI3(g) + Cl2(g) -' PCI5(g) AH298 = -88 kJ

Solved • Jul 18, 2019

Hess's Law

Q. Consider these reactions, where M represents a generic metal. 2M(s)+6HCl(aq)⟶2MCl3(aq)+3H2(g) Δ𝐻1=−622.0 kJ HCl(g)⟶HCl(aq) Δ𝐻2=−74.8 kJ H2(g)+Cl2(g)⟶2HCl(g) Δ𝐻3=−1845.0 kJ MCl3(s)⟶MCl3(aq) Δ𝐻4=−372.0 kJ Use the given information to determine the enthalpy of the reaction 2M(s)+3Cl2(g)⟶2MCl3(s)

Solved • Jul 13, 2019

Hess's Law

Q. Given that H2(g)+F2(g)⟶2HF(g) Δ𝐻∘rxn=−546.6 kJ 2H2(g)+O2(g)⟶2H2O(l) Δ𝐻∘rxn=−571.6 kJ calculate the value of Δ𝐻∘rxn for 2F2(g)+2H2O(l)⟶4HF(g)+O2(g)

Solved • Jul 12, 2019