Alcohols
5 marks · EasyThis question is about alcohols and what happens when ethanol burns in air.
Name an alcohol with three carbon atoms.
Draw the displayed formula of ethanol, showing all atoms and bonds.
Ethanol reacts with oxygen when it burns. Write the balanced chemical equation for the complete combustion of ethanol.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) propanol OR propan-1-ol OR propan-2-ol · must show correct alcohol name for 3 carbons
(b) — · must show Two-carbon chain (C–C), Five hydrogens attached properly, O–H group attached to end carbon, All bonds shown
(c) \ce{C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O(l)} · must show Balanced equation, State symbols present (not essential for full marks)
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly names an alcohol with three carbon atoms (e.g. propanol, propan-1-ol, propan-2-ol).
B2 (b) · 1 mark · Draws correct backbone of ethanol (2 carbon atoms in a chain, showing all bonds including C–C and C–O).
B3 (b) · 1 mark · Correctly shows O–H group attached to end carbon, making full displayed formula of ethanol.
B4 (c) · 1 mark · Gives correct reactants and products for combustion of ethanol, even if unbalanced.
B5 (c) · 1 mark · Gives fully balanced equation for the complete combustion of ethanol; state symbols not required but credited if correct.
Worked solution
a) An alcohol with three carbon atoms is called propanol. More precisely, it can be propan-1-ol or propan-2-ol.
b) The displayed formula for ethanol is:
All bonds are shown as lines, and the O–H group is at the end.
c) The balanced equation for the complete combustion of ethanol is: