Interpretation:
The
Concept Introduction:
Enthalpy of reaction:
The enthalpy of a reaction is calculated by subtracting the heat of formation of reactants from heat of formation of products.
Exothermic and Endothermic Reaction:
Exothermic reaction is a reaction in which heat is given out to the surrounding from the system.
Endothermic reaction is a reaction in which heat is gained by the system from the surrounding.
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Chapter 21 Solutions
General Chemistry - Standalone book (MindTap Course List)
- Comparing the chemistry of carbon and silicon. (a) Write balanced chemical equations for the reactions of H2O() with CH4 (forming CO2 and H2) and SiH4 (forming SiO2 and H2). (b) Using thermodynamic data, calculate the standard free energy change for the reactions in (a). Is either reaction product-favored at equilibrium? (c) Look up the electronegativities of carbon, silicon, and hydrogen. What conclusion can you draw concerning the polarity of CH and SiH bonds? (d) Carbon and silicon compounds with the formulas (CH3)2CO (acetone) and [(CH3)2SiO]n (a silicone polymer) also have quite different structures. Draw Lewis structures for these species. This difference, along with the difference between structures of CO2 and SiO2, suggests a general observation about silicon compounds. Based on that observation, do you expect that a silicon compound with a structure similar to ethene (C2H4) exists?arrow_forwardUse data from Appendix J to calculate the enthalpy change and the Gibbs free energy change for the reduction of chromium(III) oxide by aluminum.arrow_forwardThree reactions very important to the semiconductor industry are The reduction of silicon dioxide to crude silicon, SiO2(s) + 2 C(s) → Si(s) + 2 CO(g) ΔrH° = 689.9 kJ/mol The formation of silicon tetrachloride from crude silicon, Si(s) + 2 Cl2(g) → SiCl4(g) ΔrH° = −657.01 kJ/mol The reduction of silicon tetrachloride to pure silicon with magnesium, SiCl4(g) + 2 Mg(s) → 2 MgCl2(s) + Si(s) ΔrH° = −625.6 kJ/mol Calculate the overall enthalpy change when 1.00 mol sand, SiO2, changes into very pure silicon by this series of reactions.arrow_forward
- Calcium metal can be obtained by the direct electrolysis of molten CaCl2, at a voltage of 3.2 V. (a) How many joules of electrical energy are required to obtain 12.0 1b of calcium? (b) What is the cost of the electrical energy obtained in (a) if electrical energy is sold at the rate of nine cents per kilowatt hour?arrow_forwardUsing data in Appendix 1, estimate the temperature at which Fe2O3 can be reduced to iron, using hydrogen gas as a reducing agent (assume H2O(g) is the other product).arrow_forwardAluminum is produced commercially by the electrolysis of Al2O3 in the presence of a molten salt. If a plant has a continuous capacity of 1.00 million A, what mass of aluminum can be produced in 2.00 h?arrow_forward
- In the commercial preparation of aluminum, aluminum oxide, Al2O3, is electrolyzed at 1000C. (The mineral cryolite is added as a solvent.) Assume that the cathode reaction is Al3+3eAl How many coulombs of electricity are required to give 3.9 kg of aluminum?arrow_forwardIn an analytical determination of arsenic, a solution containing arsenious acid, H3AsO3, potassium iodide, and a small amount of starch is electrolyzed. The electrolysis produces free iodine from iodide ion, and the iodine immediately oxidizes the arsenious acid to hydrogen arsenate ion, HAsO42. I2(aq)+H3AsO3(aq)+H2O(l)2I(aq)+HAsO42(aq)+4H+(aq) When the oxidation of arsenic is complete, the free iodine combines with the starch to give a deep blue color. If, during a particular run, it takes 65.4 s for a current of 10.5 mA to give an endpoint (indicated by the blue color), how many grams of arsenic are present in the solution?arrow_forward
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