Take Home Quiz _2 KEY

# Take Home Quiz _2 KEY - KEY Take-Home Quiz#2 KEY 1(2 pts...

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KEY Take-Home Quiz #2 KEY 1. (2 pts) What is the number of moles of chloride ion in a solution prepared by mixing 20.0 mL of 0.500 M NaCl solution with 50.0 mL of a 0.200 M MgCl 2 solution? (a Ch. 4 question) 0.0300 mol Cl Approach: Calculate the number of moles of Cl ion in each solution, and then add them together. Moles = Molarity × V Liters Moles NaCl = 0.010 mol so there are 0.010 mol Cl in 1st solution Moles MgCl 2 = 0.010 mol, but since there are 2 mol of Cl per 1 mol MgCl 2 , there are 0.020 mol Cl in 2nd solution 0.010 mol Cl + 0.020 mol Cl = 0.0300 mol Cl total in new solution (3 sig. figs) 2. (2 pts) Consider the process of 1.00 kg of water cooling from 60.0 ° C to 25.0 ° C. (a) What is the heat change ( q ), in kJ , for this process? –146 kJ q = (4.184 J/g C)(1000 g)(–35.0 C) = –146,440 J = –146 kJ (b) Is the process endothermic or exothermic? Exothermic 3. (2 pts) A bomb calorimeter is used to combust substances at constant pressure. When a 2.28-g sample of octane, C 8 H 18 , is burned in a calorimeter, the temperature of the 5.00 L of water in the calorimeter is increased by 5.203

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## This note was uploaded on 01/27/2010 for the course CHM 71476 taught by Professor Marks during the Spring '10 term at ASU.

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Take Home Quiz _2 KEY - KEY Take-Home Quiz#2 KEY 1(2 pts...

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