prequiz1t.key

prequiz1t.key - Dr. Zellmer Time: 30 mins Chemistry 125...

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Dr. Zellmer Chemistry 125 Tuesday Time: 30 mins Winter Quarter 2012 January 3, 2012 Pre-quiz Name KEY Rec. TA/time. 1. (7 pts) The amount of lead, Pb, in the air on a particular day is 1.60 x 10 ! 10 lb/ft 3 . What is the mass (in kg ) of lead in 2.00 m 3 ? (1 in = 2.54 cm, 1.000 lb = 453.6 g) (You MUST use dimensional analysis to receive full credit !) 2. (8 pts) A quantity of heat equal to 600.0 cal is REMOVED from 40.0 g of water at an initial temperature of 45.0 o C. Calculate the FINAL temperature (in o C). (The specific heat of water is 1.00 cal/g C °C) Show your work . q = m C c C ) T heat (mass) C (sp. heat) C (temp. change) q = - 600.0 cal (heat is removed or released so q is negative; exothermic) Want initial temp. so must find ) T first q & 600.0 cal ) T = -------- = ----------------------------- = & 15.0 °C m C c (40.0 g)(1.00 cal/g C °C) (3 s.f.) ) T = T f & T i T f = T i + ) T 45.0 (only known to tenths) = 45.0 °C + ( ! 15.0 °C) - 15.0 ------ = 30.0 °C (3 s.f.) 30.0 (to tenths place) Copyright R. J. Zellmer, January 3, 2012
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3. (3 pts) Correctly name or write the formulas for the following compounds. Also , are they ionic or molecular? Chromium (VI) sulfide The roman numeral gives the charge on the chromium ion (+6). Cr 6+ S 2 & ==> CrS 3 IONIC For future reference, you should know how many particles (ions) you get when you put an ionic substance in water. First of all it dissociates (comes apart). That’s the easy part. You also need to remember that these polyatomic ions stay together in solutions (i.e. act as a single particle).
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This note was uploaded on 02/19/2012 for the course CHEM 125 taught by Professor Zellmer during the Winter '08 term at Ohio State.

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prequiz1t.key - Dr. Zellmer Time: 30 mins Chemistry 125...

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