The following set-up was used to investigate the percentage of oxygen in air by volume. (a) State and explain the observations made when a gas jar is inverted over the burning candle.

Step 1: Identify the reactants.
Ethanol: $\mathrm{C_2H_5OH(aq)}$ (an alcohol).
Formic acid: $\mathrm{HCOOH}$ (a carboxylic acid).

Step 2: Determine the reaction type.
This is an esterification reaction (condensation reaction between an alcohol and a carboxylic acid).
General equation:
$ROH + HOOC-R' \to R'COOR + H_2O$

Step 3: Substitute the groups.
For ethanol, $\mathrm{R = C_2H_5-}$.
For formic acid, $\mathrm{R' = H-}$.
Ester product: $\mathrm{HCOOC_2H_5}$ (ethyl formate).
Byproduct: $\mathrm{H_2O}$.

Step 4: Write the complete balanced equation.
$C_2H_5OH(aq) + HCOOH \to HCOOC_2H_5 + H_2O$

\mathrm{C_2H_5OH(aq) + HCOOH \to HCOOC_2H_5 + H_2O}