"A graph is shown with the label, ""Extent of reaction,"" appearing in a right pointing arrow below the x-axis and the label, ""Energy,"" in an upward pointing arrow just left of the y-axis. Approximately one-fifth of the way up the y-axis, a very short, somewhat flattened portion of both a red and a blue curve are shown. This region is labeled ""Reactants."" A red concave down curve extends upward to reach a maximum near the height of the y-axis. From the peak, the curve continues downward to a second horizontally flattened region at a height of about one-third the height of the y-axis. This flattened region is labeled, ""Products."" A second curve is drawn in blue with the same flattened regions at the start and end of the curve. The height of this curve is about two-thirds the height of the first curve and just right of its maximum, the curve dips low, then rises back and continues a downward trend at a lower height, but similar to that of the red curve. A horizontal dashed straight line extends from the point where both curves start in the ""Reactants"" region. A double sided arrow extends from the ""Products"" region at the end of both curves to this horizontal dashed line. This is labeled ""capital delta H."" A double sided arrow extends from the dashed horizontal line to the peak of the red concave down curve. This arrow is labeled ""E subscript a."" Another double sided arrow extends from the dashed horizontal line to the peak of the blue curve. This arrow is labeled ""E subscript a."""
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