$$$ Quiz $$$ Thermochemistry. Gives off heat (emits) exothermic.
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Transcript of $$$ Quiz $$$ Thermochemistry. Gives off heat (emits) exothermic.
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$$$ Quiz $$$
Thermochemistry
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Gives off heat (emits)
exothermic
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Absorbs heat
endothermic
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It flows from hot to cold objects and is known by the letter “q”
heat
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The study of energy changes that occur during chemical reactions
thermochemistry
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What is a calorie or joule?
Unit of heat (q)
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Defined as the amount of heat needed to increase the temperature of an object by 1oC.
Heat capacity
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Defined as the amount of heat needed to increase 1 gram of an object by 1oC.
Specific heat or specific heat capacity
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The formula for q?
q = C x m x T
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Solve the previous equation for the other three variables.
C = q/mTm = q/CTT = q/Cm
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A balance bar has 200 Calories. How many kilojoules is this? How
many joules is this?
836.8 kj836,800 joules
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True or False. cal/oC is an acceptable unit for specific heat.
False, cal/goC
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True or False. Metals generally have a higher specific heat
capacity than water.
False
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True or False. Metals generally have a higher specific heat capacity
than molecular compounds.
False
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You measure 1200 joules of heat during a 30oC temperature change with a
substance that weighs 100 g. What is the specific heat of the substance.
0.40 J/goC
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During a phase change, the temperature of a substance ________.
Remains constant
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A calorimeter can effectively measure the heat of another
substance because of the ____________?
Law of Conservation of Energy
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H of fusion involves which phase change?
Melting
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H of solidification involves which more commonly known phase change?
Freezing
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If the percent mass of a solution weighing 300 g is 6%, what is the
mass of the solute?
.06 = x/300gx = 18 g
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The heat content of a system at a constant pressure is known as the
________ of that system.
enthalpy
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What is the enthalpy change in a chemical reaction known as?
Heat of reaction, H
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If the H of a reaction is negative then the reaction is _______ .
exothermic
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The heat of the reaction for the complete burning of one mole of a substance.
Heat of combustion
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The enthalpy change when a mole of solute is dissolved in a solvent.
Heat of solution
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True or False. The quantity of heat absorbed when a solid melts is the
same as the quantity released when the substance freezes.
True. Hfus = -Hsolid.
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What makes Hess’s law useful?
It allows you to determine heats of reactions indirectly
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The change in enthalpy that involves the formation of one mole of a compound from its
elements (at 25oC) is known as?
Standard heat of formation, (Hf
o)
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True or False. The standard heat of a reaction can be calculated
by the following equation …Ho = Hf
o(products) - Hf
o(reactants)
True