Which is evidence that a chemical reaction has occured. a. a phase change occurs b. a new gas is observed in the form of bubbles c. red and yellow paint mixing to make orange paint d. the temperature of the substance remains constant

Problem page combustion of hydrocarbons such as pentane ( c5 h12 ) produces carbon dioxide, a "greenhouse gas." greenhouse gases in the earth's atmosphere can trap the sun's heat, raising the average temperature of the earth. for this reason there has been a great deal of international discussion about whether to regulate the production of carbon dioxide.(a) write a balanced chemical equation, including physical state symbols, for the combustion of liquid pentane into gaseous carbon dioxide and gaseous water. (b) suppose 0.350 kg of pentane are burned in air at a pressure of exactly 1 atm and a temperature of 20.0 degree c. calculate the volume of carbon dioxide gas that is produced.be sure your answer has the correct number of significant digits.

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8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.