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HW key _3 S problems part a

# HW key _3 S problems part a - S3 From the following...

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S3. From the following information below, determine the mass of substance C that will be formed if 45.0 g of substance A reacts with 23.0 g of substance B. (Assume that the reaction between A and B goes to completion.) a. Substance A is a gray solid that consists of an alkaline earth metal and carbon (37.5% by mass). It reacts with substance B to produce substances C and D. Forty million trillion formula units of A have a mass of 4.26 mg. b. 47.9 g of substance B contains 5.36 g of hydrogen and 42.5 g of oxygen. c. When 10.0 g of substance C is burned in excess oxygen, 33.8 g of carbon dioxide and 6.92 g of water are produced. A mass spectrum of substance C shows a parent molecular ion with a charge-to-mass ratio of 26. d. Substance D is the hydroxide of the metal in substance A. To determine the amount of C that will be formed we need to know the limiting reagent in the reaction; however, to do this we first need to know what each of the reactants and products are so that we can balance the equation. a. 40 million trillion = = 40 × 10 6 × 10 12 = 4.000 × 10 19 where we have used 4 S.F. 4.000 × 10 19 moleulces of A × 1 mol A 6.022 × 10 23 = 6.642 × 10 5 mol A Molar mass of A = 4.26 × 10 3 g A 6.642 × 10 5 mol A = 64.1 g/mol The mass of carbon in one mole of A is 64.1 g A × 37.5 g C 100.0 g A = 24.0 g carbon = 2 molcarbon in substance A The remainder of the molar mass (64.1 g – 24.0 g = 40.1 g) is due to the alkaline earth metal. From the periodic table, calcium has a molar mass of 40.08 g/mol; therefore, the formula of substance A is CaC 2 .

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