Problems
1) A 300 grain bullet is traveling with a velocity of 252 ft/s. Calculate the associated kinetic energy given that 1 grain is equal to 0.0648 grams and 1 m is equal to 3.28 ft.
2) Define an exothermic reaction and an endothermic reaction.
3) When 1 mol of iron reacts with hydrochloric acid at a constant temperature and pressure it produces hydrogen gas and aqueous (aq) iron (II) chloride and releases 89.1 kJ of heat. Write a thermochemical reaction for the process.
4) Propane, C3H8 is a common gas that is used as fuel, use the following thermochemical equation to predict how many grams of propane you would need to produce 530 kJ of heat.
C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O (g); ΔH = -2043 kJ/mol
5) How much heat is required to raise the temperature of 0.350 kg of water from 25 to 95 degrees Celsius, given the specific heat of water is 4.18 J/g*C.
Answers
1) Kinetic energy is equal to 1/2mv2
300 grains x (0.0645 g/1 grain) = 19.4 g x (1 kg/1000g) = 0.0194 kg
252 ft/s x (1 m/3.28 ft) = 76.8 m/s
KE = 1/2(0.0194 kg)(76.8m/s)2 = 57.2 J
2) An exothermic reaction releases energy from the system to the surroundings and an endothermic reaction absorbs energy into the system from the surroundings.
3) Fe (s) + 2HCl (aq) -> FeCl2 (aq) + H2(g); ΔH = -89.1 kJ/mol
4) -530 kJ x (1mol C3H8/-2043 kJ) x (44.08 g/1mol) = 11.4 grams C3H8
5) q = msΔT = (0.350kg)(4180J/g*C)(95-25C) = 1.02 x105 J