JAMB - Chemistry (2024 - No. 103)
After breathing in a test tube that contains acidified K\(_2\)Cr\(_2\)O\(_7\), a man noticed the change in the colour of K\(_2\)Cr\(_2\)O\(_7\) from orange to green. This suggests the presence of
alkanone
alkanal
alkanol
alkanoic acid
Explanation
When an alcohol is oxidized in a warm solution of potassium dichromate (VI) and dilute sulphuric acid, the solution changes colour from orange to green. This is because the Cr\(_2\)O\(_7\)\(^{2-}\) ions in the solution are reduced to Cr\(^{3+}\) ions. This colour change can be used to identify alcohols. Only alcohols will cause the solution to change colour from orange to green.