C1.90 Thermo Practice Test Alex D per 6

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Green River College *

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MISC

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Chemistry

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Feb 20, 2024

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Name: ___Alex Deegan________________________ Period: _6_ Chapter 15: Thermochemistry Study Guide and Practice Test Be able to define and use these terms (in addition to all terms in previous units): Energy Conservation of Energy Spontaneity/ Entropy Heat Calorie/calorie/joule Specific Heat Calorimeter System Surroundings Enthalpy Enthalpy of reaction Thermochemical Equation Enthalpy of Combustion Enthalpy of vaporization Enthalpy of fusion Moles * H = energy (Q) Calculations. Show all work (including units). Solve for variables before plugging in numbers. How much heat must be put into a 20.00 g sample of water to change the temperature from 283.0 o C to 303.0 o C? 20x20x4.184= 1673.6kj How much energy is released when 1250 g of water vapor condenses? 1250/18.016=69.4 40.7x69.4mol= -2820 A 755 g sample of liquid water is cooled from 75.3 o C to 0.00 o C, it then freezes completely into a solid at the freezing point. How much energy is released for the ENTIRE process? 755x75.3x4.184=238000j/100=238k=252k Convert 37.2 kJ into J 37200j Convert 57.0 calories in Joules 57/.2390=238 Convert 17,400 Joules into Calories 4158.6 cal Convert 18.2 kJ into calories
18,200x0.238=4348.8 cal A chemical reaction in which the reactants are at a lower energy level than the products is endothermic/exothermic. endothermic An industrial transport railcar can hold 48,200 kilograms of methane (CH 4 ). How much energy could be released if all of this combusted in excess oxygen (air)? 41,840 Joules of heat is put into a water sample, increasing the temperature from 22.0 o C to 28.5 o C. Find the mass (g) of the water. 41840= 6.5x4.184=1540g A sample of iron at an initial temperature of 99.4 o C is placed into a simple calorimeter with 50.0 mL of water at a starting temperature of 21.0 o C. After heat flows from the hot metal into the water, both are at a temperature of 30.0 o C. What is the mass of the iron? 50.8x9xo.4184/-69.4x o.449=60.4g How much energy is required to vaporize 12.5 kg of ethanol (C 2 H 5 OH)? 12500/46.07=271.33mol 271.33x38.6=10,500k Oooh, Hard ONE! 150.0 grams of iron at an initial temperature of 95 o C is placed in an insulated container filled with 500.0 grams of water at a starting temperature of 25.0 o C. What will the final temperature of the iron and water be? (500x4.184xT)(150x0x448x70) 2.2+25= 27.2 c Challenge section 1) When 1 mole of hydrogen gas reacts with excess oxygen to form water at a constant pressure, then 241.8 kJ of energy is released as heat. Calculate H for the same reaction with there is 15.0 grams of hydrogen gas.
2) Calculate the enthalpy for the following reaction: N 2 (g) + 2O 2 (g) ---> 2NO 2 (g) H ° = ??? kJ Using the following two equations: N 2 (g) + O 2 (g) ---> 2NO(g) H ° = +180 kJ NO 2 (g) ---> NO(g) + 1 / 2 O 2 (g) H ° = +56 kJ
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