The Effect of Temperature on Volume Measurements
المؤلف:
D. A. Skoog, F. J.Holler, D M. West, and S. R. Crouch
المصدر:
Fundamentals of Analytical Chemistry
الجزء والصفحة:
9th p35
5-4-2016
2768
The Effect of Temperature on Volume Measurements
The volume occupied by a given mass of liquid varies with temperature, as does the device that holds the liquid during measurement. Most volumetric measuring devices are made of glass, which fortunately has a small coefficient of expansion. Thus, variations in the volume of a glass container with temperature need not be considered in ordinary analytical work.
The coefficient of expansion for dilute aqueous solutions (approximately 0.025%/°C) is such that a 5°C change has a measurable effect on the reliability of ordinary volumetric measurements.
Example
A 40.00-mL sample is taken from an aqueous solution at 5°C. What volume does it occupy at 20°C?
V20° = V5° + 0.00025(20 - 5)(40.00) = 40.00 + 0.15 = 40.15 mL
Volumetric measurements must be referred to a standard temperature, often 20°C. The ambient temperature of most laboratories is usually close enough to 20°C so that there is no need for temperature corrections in volume measurements for aqueous solutions. In contrast, the coefficient of expansion for organic liquids may be large enough to require corrections for temperature differences of 1°C or less.
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