What action in the solute-dissolving step can reduce percent recovery?

In the context of solute-dissolving steps, not using the solvent at its boiling point can significantly impact the percent recovery. When a solvent is heated to its boiling point, it allows for maximum solubility of the solute. This is especially important for compounds with high melting or boiling points that require higher temperatures to dissolve efficiently.

If the solvent is not used at its boiling point, the solubility of the solute may be insufficient. This can lead to incomplete dissolution, resulting in a portion of the solute remaining undissolved. Consequently, during the recovery phase, any undissolved solute will not be collected, thus decreasing the overall recovery percentage.

In contrast, the other options may not have the same detrimental effects on percent recovery. Using too much solvent may dilute the solution but could still lead to complete dissolution. Heating the solvent for too long can lead to degradation or loss of volatile compounds but does not necessarily prevent all solute from dissolving. Rapid cooling of the solvent may promote crystallization, which can be beneficial for recovery, depending on the nature of the compound being isolated.