# 0 g water initially at a temperature of 200 o c

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C is immersed in 100.0 g water . initially at a temperature of 20.0 o C . Ignore any minor heat loss to the air or calorimeter. m H2O c H2O   = - m m c m  m second version using incorrect value for Cu c = 0.0835 100 x 4.184 x ( T f - 20.0 ) = -80 x 0.232 x (T f - 200.0) . 418.4T 8368 = -18.56T + 3712 . 437 T = 12080 third version using correct value for c = 0.385 5. An 80.0 g piece of Ag/Au alloy d= 14.9 g/cm3version 2 Cu/Au 13.6 g/cm3 V = 80/13.6 = 5.88 ml. . . immersed in water so V = 80/14.9 = 5.37 ml version 3 Cu/Au 14.1 g/cm 3 80/14.1 = 5.67 mL a) Predict how many grams it will appear to weigh once immersed in water . (dH2O= 1.00 g/mL). b) If ethanol ( d = 0.790 g/mL) is used as the liquid for immersion, how many grams will the metal piece 80.0 5.37 = 80 5.88 = 80 5.67 = .. appear to weigh ? displaced 5.37mL x 0.790 g/mL = 4.24 g weight lost etc 1.2 x 10 7 17.1 g/cm 3 Diameter = 6.54 cm 24.3 T f = 21.3 C 74.6 g 75.8 g 1.25 x 10 -7 14.9 g/cm 3 5.46 cm T f = 27.6 C T f = 32.4 74.1g 74.3 g
** c) bonus . What is the % composition of the alloy ? (% Ag, % Au ) Let x = d Ag = 10.5 g/cm 3 or x = d Cu = 8.92 10.5x + 19.3y = 14.9 Let y = d Au = 19.3 g/cm 3 10.5 x + 19.3(1-x) = 14.9 6. Name these elements: refer to a periodic table, a) Mn b) Si c) Sn d) Ni e) Hg f) Pb 7. What are two allotropes of oxygen O , O 2 , O 3 What are two allotropes of carbon ? C 60 , (fullerene) Graphite , diamond 8. Name these items from your locker.( 3 pts) (complete names) a ) __wash bottle____ b) __Erlenmeyer flask____ c) __evaporating dish___ 9. Which of these graphs describe an inversely proportional relationship between x and y ?

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• Fall '19
• Atom, E Rutherford

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