Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

An experiment was carried out to find the enthalpy of combustion of ethanol. The recorded data are: mass of water $= W\,\text{g}$; mass of ethanol burned $= X\,\text{g}$; temperature rise $= Y^{\circ}\text{C}$; molar mass of ethanol $= Z\,\text{g mol}^{-1}$; specific heat capacity of water $= 4.2\,\text{J K}^{-1}\text{g}^{-1}$. Which expression may be used to work out the enthalpy of combustion of ethanol in $\text{kJ mol}^{-1}$?

  • A$\frac{-4.2WYZ}{1000X}$
  • B$\frac{-4.2WYX}{1000Z}$
  • C$\frac{-4.2XYZ}{1000W}$
  • D$\frac{-4.2X(Y+273)Z}{1000W}$

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