Alcohols

5 marks · Easy

This question is about alcohols and what happens when ethanol burns in air.

(a)

Name an alcohol with three carbon atoms.

[1 mark]

(b)

Draw the displayed formula of ethanol, showing all atoms and bonds.

[2 marks]

(c)

Ethanol reacts with oxygen when it burns. Write the balanced chemical equation for the complete combustion of ethanol.

[2 marks]

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: