Question #99f0f

1 Answer
Apr 23, 2017

The temperature change will be +9 °C.

There are two heats to consider:

#"heat released by combustion + heat absorbed by water" = 0#

#q_1 + q_2 = 0#

#nΔ _text(r)H+ mcΔT = 0#

In this problem,

#n = 3.2 color(red)(cancel(color(black)("g propane"))) × "1 mol propane"/(44.10 color(red)(cancel(color(black)("g propane")))) = "0.0726 mol propane"#

#Δ_text(r)H = "-2220 kJ/mol"#

#m = "mass of water" = "4000 g"#

#c = "4.184 J°C"^"-1""g"^"-1"#.

#q_1 = 0.0726 "mol" × "-2 200 kJ"/(1 "mol") = "-160 kJ"#

#q_2 = 4000 cancel("g") × "4.184 J°C"^"-1"cancel("g"^"-1") × ΔT = "17 000 J°C"^"-1" × ΔT = "17 kJ°C"^"-1" × ΔT#

#"-160" color(red)(cancel(color(black)("kJ"))) + 17 color(red)(cancel(color(black)("kJ")))"°C"^"-1" × ΔT = 0#

#ΔT = 160/("17 °C"^"-1") = "9 °C"#