Many nitrate salts can be decomposed by heating. For example, blue, anhydrous copper(II) nitrate produces the gases nitrogen dioxide and oxygen when heated. In the laboratory, you find that a sample of this salt produced a 0.195-g mixture of gaseous NO₂ and O₂ with a total pressure of 725 mm Hg at 35°C in a 125-mL flask (and black, solid CuO was left as a residue). What is the average molar mass of the gas mixture? What are the mole fractions of NO₂ and O₂ in the mixture? What amount of each gas is in the mixture? Do these amounts reflect the relative amounts of NO₂ and O₂expected based on the balanced equation? Is it possible that the fact that some NO₂ molecules combine to give N₂O₄ plays a role?

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ⒸCengage Learning/Charles D. Winters Heating copper (II) nitrate produces nitrogen dioxide and oxygen gas and leaves a residue of copper (II) oxide.