QCA7e_ch01_szb_handouts

QCA7e_ch01_szb_handouts - Daniel C. Harris Quantitative...

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1 Quantitative Chemical Analysis Seventh Edition Quantitative Chemical Analysis Seventh Edition Chapter 1 Measurements Daniel C. Harris Daniel C. Harris Topics in this Chapter • units of measurement • chemical concentrations • preparation of solutions • stoichiometry of chemical reactions
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2 An Ultrasensitive Measurement • Atomic absorption signal from 60 gaseous rubidium atoms observed by laser wave mixing. • A 10-microliter (10 × 10 6 L) sample containing 1 attogram (1 × 10 18 g) of Rb + was injected into a graphite furnace to create the atomic vapor. Système International d'Unités
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3 Système International d'Unités Prefixes • Rather than using exponential notation, we often use prefixes to express large or small quantities.
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4 Use of prefixes • At an altitude of 1.7 × 10 4 meters above the earth's surface, the pressure of ozone over Antarctica reaches a peak of 0.019 Pa. Let's express these numbers with prefixes: • We customarily use prefixes for every third power of ten (10 9 , 10 6 , 10 3 , 10 3 , 10 6 , 10 9 , etc) • The number 1.7 × l0 4 m is more than 10 3 m and less than 10 6 m, so we use a multiple of 10 3 m (= kilometers, km): Use of prefixes • At an altitude of 1.7 × 10 4 meters above the earth's surface, the pressure of ozone over Antarctica reaches a peak of 0.019 Pa. Let's express these numbers with prefixes: • We customarily use prefixes for every third power of ten (10 9 , 10 6 , 10 3 , 10 3 , 10 6 , 10 9 , etc) • The number 0.019 Pa is more than 10 3 Pa and less than 100 Pa, so we use a multiple of 10 3 Pa (= millipascals, mPa):
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5 Example for conversions • Express the rate of energy used by a person walking 2 miles per hour (91 Calories per hour per 100 pounds of body mass) in kilojoules per hour per kilogram of body mass. Solution: First, note that 91 Calories equals 91 kcal. Table 1-4 states that 1 cal = 4.184 J; so 1 kcal = 4.184 kJ, and • Table 1-4 also says that 1 lb is 0.453 6 kg; so 100 lb = 45.36 kg. The rate of energy consumption is therefore • We could have written this as one long calculation:
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6 Chemical Concentrations • A solution is a homogeneous mixture of two or more substances. • A minor species in a solution is called solute and the major species is the solvent. • Most of our discussions concern aqueous solutions, in which the solvent is water. Concentration states how much solute is contained in a given volume or mass of solution or solvent. Molarity and Molality • A mole (mol) is Avogadro's number of particles. Molarity (M) is the number of moles of a substance per liter of solution. – A liter(L) is the volume of a cube that is 10 cm on each edge. – Because 10 cm = 0.1 m, 1 L = (0.1 m)
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QCA7e_ch01_szb_handouts - Daniel C. Harris Quantitative...

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