Heptane is an alkane with the chemical formula C7H16. As a hydrocarbon, it can undergo hydrocarbon combustion which gives off heat energy. Heptane is a volatile, colourless liquid that is odourless when pure.[2] Heptane is an important hydrocarbon (or organic molecule as it, along with pure octane, sets the extreme ends of the octane rating scale. Heptane is used to set the standard zero point. This means that as a fuel it burns in a way that is unhelpful within an engine, specifically, it combusts when put under pressure. This is why higher octane ratings are better for an engine. Heptane is a terrible fuel choice for a car since it burns explosively, causing engine knocking. As well as setting the zero point for octane rating, heptane is frequently used as a laboratory solvent due to it's low reactivity with other molecules. Many substances that will not dissolve in water do dissolve in heptane.[3] PropertiesBelow is a table of some of the basic properties of heptane. Combustion ReactionHeptane undergoes hydrocarbon combustion, combining with oxygen to form carbon dioxide. The balanced chemical equation for the complete combustion of heptane is: C7H16 + 11O2 → 7CO2 + 8H2O + Heat Energy (Enthalpy)
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PROBLEM \(\PageIndex{1}\) Determine the empirical formulas for compounds with the following percent compositions: (a) 15.8% carbon and 84.2% sulfur CS2 CH2O
PROBLEM \(\PageIndex{2}\) Determine the empirical and molecular formula for chrysotile asbestos. Chrysotile has the following percent composition: 28.03% Mg, 21.60% Si, 1.16% H, and 49.21% O. The molar mass for chrysotile is 520.8 g/mol. AnswerMg3Si2H3O8 (empirical formula), Mg6Si4H6O16 (molecular formula)
PROBLEM \(\PageIndex{3}\) Polymers are large molecules composed of simple units repeated many times. Thus, they often have relatively simple empirical formulas. Calculate the empirical formulas of the following polymers: (a) Lucite (Plexiglas); 59.9% C, 8.06% H, 32.0% O (b) Saran; 24.8% C, 2.0% H, 73.1% Cl (c) polyethylene; 86% C, 14% H (d) polystyrene; 92.3% C, 7.7% H (e) Orlon; 67.9% C, 5.70% H, 26.4% N Answer aC5H8O2 Answer bCHCl Answer cCH2 Answer dCH Answer eC3H3N
PROBLEM \(\PageIndex{4}\) A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 75.95% C, 17.72% N, and 6.33% H by mass with a molar mass of about 240 g/mol. Determine the molecular formula of the dye. AnswerC15H15N3 Contributors |