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Scan_Doc0030 - scale we will use Equation(l.3 TF 40 9P-=-Tc...

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24 Chapter One Chemical Foundations Since, as shown in Example 1.12, -40° on both the Fahrenheit and Celsius scales represents the same temperature, this point can be used as a reference point (like O°Cand 32°F) for a relationship between the two scales: Number of Fahrenheit degrees Number of Celsius degrees TF - (-40) Tc - (-40) 9°F sec (1.3) TF + 40 Tc + 40 9°F 5°C EXAMPLE 1.13 Liquid nitrogen is so cold that water condenses out of the surrounding air, forming a cloud as the nitrogen is poured. where TF and Tc represent the same temperature (but not the same number). This equa- tion can be used to convert Fahrenheit temperatures to Celsius, and vice versa, and may be easier to remember than Equations (1.1) and (1.2). Liquid nitrogen, which is often used as a coolant for low-temperature experiments, has a boiling point of 77 K. What is this temperature on the Fahrenheit scale? Solution We will first convert 77 K to the Celsius scale: Tc = TK - 273.15
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Unformatted text preview: scale, we will use Equation (l.3): TF + 40 9P--=-Tc + 405C TF + 40 = TF + 40 = 9F-196C + 40-156C 5C 9F T, + 40 = -(-156C) =-281F F 50C TF =-281F-40 =-321F SEE EXERCISES 1.53, 1.55, AND 1.56 J..8 ~ Density A property of matter that is often used by chemists as an "identification tag" for a sub-stance is density, the mass of substance per unit volume of the substance: mass Density = volume The density of a liquid can be determined easily by weighing an accurately known vol-ume of liquid. This procedure is illustrated in Example 1.14. EXAMPLE 1.14 A chemist, trying to identify the main component of a compact disc cleaning fluid, finds that 25.00 crrr' of the substance has a mass of 19.625 g at 20C. The following are the names and densities of the compounds that might be the main component:...
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