Find the temperature increase in #""^@ "C"# expected for #"1.00 L"# of water when it absorbs all of the energy from the combustion of #"1.00 g"# of acetylene, #"C"_2"H"_2(g)#? (Every mole of acetylene releases #"1300 kJ"# of energy when combusted.)

#a)# #11.8^@ "C"#
#b)# #14.1^@ "C"#
#c)# #15.5^@ "C"#
#d)# #13.4^@ "C"#
#e)# #13.6^@ "C"#

1 Answer
Jane
Jan 25, 2018
  1. 11.8

Explanation:

Molecular weight of acetylene is #(12*2+2*1#) or #26 gm#

So, #26 gm# of acetylene contain #1# mol,hence #1 gm# contain #1/26# mole

Now, if per mole acetylene releases #1300 KJ# of energy then,for #1/26# moles energy released will be #((1300*10^3)/4.2)*(1/26)# Calorie.

Now,this amount of heat(#H#) will be taken up by #1 liter# of water,

#1 liter = 1000 cm^3# and density of water is #1(gm)/(cm^3)#

So,mass of #1 liter# of water is #1000 gm#(as, mass = volume*density)

So, we can apply #H= ms d theta# (where #m# is the mass of water,#s# is specific heat of water and its value is 1 CGS unit, and #d theta# is the change in temperature)

Putting the values we get, #d theta# = #11.9# degree C

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