10. In a typical household, about one-quarter of the energy con water. (a) What

Question

10. In a typical household, about one-quarter of the energy con water. (a) What mass of methane undergoing complete combust (b) How might we heat water more efficiently? (c) What alternative energy resources are available for he 100.0 kg of water from 5.0°C to 70.0°C in a gas water h Section 5.5 Questions Understanding Concepts Write balanced equations for the formation of the following: (a) acetylene gas (C2H2), used in welding (b) creatine (C HgNg02). used as a food supplement (c) potassium iodide (KI, used as a salt substitute (d) ironOD sulfate (FeSO,J, used as a diet supplement Use standard enthalpies of formation to calculate the enthalpy changes in each of the following equations: (a) Magnesium carbonate decomposes when strongly heated. (b) Ethene burns in air. (c) Sucrose (C12H22011 decomposes to carbon and water vapour when concentrated sulfuric acid is poured onto it Figure 4). 3. When octane is strongly heated with hydrogen gas in the presence of a suitable catalyst, it “cracks," forming a mix- ture of hydrocarbons. A typical cracking reaction yields 1 mol of methane, 2 mol of ethane, and 1 mol of propane from each mole of octane. EL

Explanation / Answer

Formation of chemicals from their constitutent elements is not an efficient method for preparing many compounds as they many react through many steps and intermediates that result in formation of more than one product. In fact in numerous occassions, the required product may not even be formed from the elements. However, when completely ignoring the side reactions and products, the formation of the given compounds are given below.

Equations such as those given below are balanced to obey the law of mass conservation which gives that in a chemical reaction, the moles of all elements are conserved throughout the chemical reactions implying the need for differing equivalents of different elements or compounds in a reaction to ensure complete consumption of all reactants. Thus the equations are balanced with the minimum possible integer.

1. 2C + H2 -----> C2H2

2. 8C + 9H2 + 3N2 + 2O2 -----> 2C4H9N3O2

3. 2K + I2 -----> 2KI

4. 8Fe + S8 + 16O2 -----> 8FeSO4

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