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Chemistry. Unit 2 Lesson 3. Derived quantities (page 23). Derived Quantity: A number made by combining two or more other values. Derived unit: a unit which is made by combining two or more units. Example 1: Gas law: PV = nRT, P = Pressure (atm). V = Volume (L). n = mol
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Chemistry Unit 2 Lesson 3
Derived quantities (page 23) • Derived Quantity: A number made by combining two or more other values. • Derived unit: a unit which is made by combining two or more units.
Example 1: • Gas law: PV = nRT, • P = Pressure (atm). • V = Volume (L). • n = mol • R = Gas constant = Latm/Kmol). • T = Temperature in Kelvin (273.15 K = 0 ºC). • Solve for T • T = PV/nR • T is the derived quantity having the derived units of K (Latm/(Latm/Kmol X mol)).
Density. • Mass (m) = the quantity of matter in an object. • Density = the mass contained in a given volume of substance. • Break down what is being said --- mass/volume; thus, d = m/V • What are the units of density?
Example • A rock has a mass of 0.2 kg and a volume of 400 mL. What is the density of the rock? Hint, density is usually measured in g/mL. • Set up the equation. • d = g/mL. • convert kg to g while dividing by mL. • d = (0.2 kg) * (1 g / 10-3 kg) * (1 / 400 mL) = 0.5 g/mL
Example 2 • The density of Beryllium is 1.85 g/mL. Calculate the mass of a 0.75 L chunk of Be. • Change L to mL 0.75L = 750 mL • M = DV 1.85 g/mL x 750 mL = 1387.5 g (1.39 Kg)
Homework • 29 a, d. (Page 23) • 31 – 35, 39 (Page 26)