Final answer:
Samples with absorbance readings above 1.0 should indeed be diluted for accurate measurements when using a standard curve. As absorbance readings are linear within a specific range, dilution ensures readings fall within the calibrated and reliable range for accurate concentration estimation.
Step-by-step explanation:
If unknown samples give a reading above a 1.0 absorbance, one should indeed dilute the samples to accurately utilize the standard curve. Absorbance readings on a spectrophotometer are typically linear within a certain range. When a sample's absorbance exceeds this range, the reading can become inaccurate or the spectrophotometer may become saturated, incapable of giving a reliable value. To ensure accurate measurements, samples should be diluted so that their absorbance readings fall within the linear range of the standard curve.
This practice enables the experimenter to use the calibration curve created by measuring absorbance at different concentrations to determine the unknown concentration of the sample in question. The standard curve is generated by plotting known concentrations against their corresponding absorbance values. By diluting the sample, you are effectively adjusting its concentration to a range that has been previously calibrated, which allows for an accurate estimation of concentration using the curve.