NESA Chemistry Analysis of Organic Substances

This is a solution of Iron(III) nitrate. Neither $Fe^{3+}$ nor $NO_3^-$ ions react with bromine water, so the solution would not be decolourised.

Chloride ions ($Cl^-$) cannot reduce bromine ($Br_2$) because chlorine is a stronger oxidising agent than bromine. Therefore, no reaction occurs to remove the bromine colour.

3-methylbutanoic acid has four unique sets of protons, which would produce a singlet (OH), a doublet (CH3 groups), a multiplet/nonet (CH), and another doublet (CH2).

2-chloro-2-methylpropane has only one unique set of protons (nine equivalent methyl protons), which would produce a single peak (singlet) in its $^1\text{H}$ NMR spectrum.

1,2-dichloro-2-methylpropane has two unique sets of protons that are not adjacent to any other protons, which would result in a spectrum with two singlets.

Bromine water is used to test for the presence of carbon-carbon double bonds (unsaturation). It would not react with either of these saturated alcohols.

Potassium nitrate is generally unreactive with alcohols and would not produce a visible change to help distinguish between the two substances.

Sodium carbonate is typically used to test for acidic substances like carboxylic acids by observing effervescence (carbon dioxide gas), but it does not react with alcohols.

IR radiation causes changes in the vibrational states of molecules, not the spin states of electrons (which is associated with Electron Paramagnetic Resonance spectroscopy).

The wavenumber of a bond's vibration depends on both the bond strength (force constant) and the reduced mass of the atoms involved, as described by Hooke's Law.

Transmittance and absorbance are inversely related; high transmittance means that most of the light passed through the sample, indicating low absorption.

Dichromate is a strong oxidizing agent used to test for primary and secondary alcohols or aldehydes, but carboxylic acids are already fully oxidized at the carbon atom and will not react.

Bromine water is used to test for unsaturation (such as alkenes and alkynes) or highly activated aromatic rings, not carboxylic acids.

Sodium sulfate is a neutral salt and does not undergo an acid-base reaction with weak acids like carboxylic acids.

While HPLC can be used qualitatively to identify substances based on retention time, this option is incomplete because HPLC is also a quantitative technique.

While HPLC can be used quantitatively to determine concentration based on peak area, this option is incomplete because HPLC is also a qualitative technique.

Statement III is incorrect because triplets refer to splitting patterns found in Nuclear Magnetic Resonance (NMR) spectroscopy, not HPLC.

Amines are basic compounds and do not react with sodium hydrogen carbonate to produce carbon dioxide.

Haloalkanes do not have acidic properties sufficient to react with sodium hydrogen carbonate to release carbon dioxide.

Alcohols are weaker acids than carbonic acid and do not react with sodium hydrogen carbonate to evolve carbon dioxide.

The relative molecular mass is determined from the molecular ion peak ($M^+$), whereas the base peak simply represents the most abundant ion fragment.

While isotopes cause specific adjacent peaks (like $M+1$), the vast majority of peaks in a mass spectrum are caused by the fragmentation of the molecule into smaller ions.

The base peak is simply the most intense peak representing the most stable ion; it can sometimes be the intact molecular ion itself, meaning no uncharged species was removed.