Quiz: Heat, Q and Hrxn

questions/calculations

Take out your table with Hformation values on it.

Be Able to:

• Determine and explain endothermic/exothermic processes

• Calculate using Q and H values• Describe the three types of heat transfer:– Radiation– Convection– Conduction

How much heat is released when 2.00 moles of water freeze?

• -12.0 kJ of heat

How much energy is needed or released to combust 64.0 g of methane if it has a heat of combustion value of -891 kJ/mol?

•Use dimensional analysis•-3564 kJ

842 kJ of energy is released by the combustion of an unknown amount of glucose (C6H12O6); How much glucose (in grams) was combusted? Hcomb = -2808 kJ/mol•Use dimensional analysis•54.0 g

What is the specific heat of a substance whose temperature changes from 35.0oC to 78.5oC when it absorbs 625 J of heat if its mass is 45.6g?

•Use Q = mcT•0.315 J/goC

If 335g of water is initially at 65.5 degrees Celsius loses 9750 J of heat, what is the final temperature of the water?

•Use Q = mcT•Solve for Tfinal•58.5 Degrees Celsius

15.0 g of water at 0.00 degrees Celsius is added to 45.0g of water at 40.0 degrees Celsius. What is the final temperature of the water mixture?

•Use Q = mcT (2X)•Qwater1 = -Qwater2•29.1oC

Calculate the Hrxn of the reaction of ammonia (NH3) decomposing to form nitrogen and hydrogen gases. Is it an exothermic or endothermic

rxn? • 2NH3(g) 3H2(g)+ N2(g)

• Hrxn = Products – Reactants (*Get values from chart)

• 92.22 kJ• Endothermic

Calculate the Hrxn for the reaction of sulfur dioxide gas with oxygen

gas to form sulfur trioxide gas. Is it an exothermic or endothermic

process? • 2SO2(g) + O2 2SO3(g)

• Hrxn = Products – Reactants (*Get values from chart)

• -316 kJ• Exothermic