When acetaldehyde is treated with dil.NaOH it undergoes self condensation as it contains alpha-hydrogen atom in its compound forming β-hydroxyaldehyde (an aldol) namely 3-Hydroxy butanal. This compound upon further heating will eliminate a molecule of water forming aldol condensation product namely Crotonaldehyde Or But-2-en-al. see the diagram attached.
Answer: the scientist should ensure that the volume is measured in dm3(or L), the pressure in atm, the temperature in Kelvin and use the gas constant 0.082atm.dm3.K^-1.mol^-1