An organic compound 'X' having molecular formula C₅H₁₀O yields phenyl hydrazone and gives negative response to the Iodoform test and Tollen's test. It produces n-pentane on reduction. What is ‘X’?

3-Pentanone 

An organic compound 'X' Having molecular formula C₅H₁₀O yields phenyl hydrazone. This indicates presence of carbonyl group.

It gives negative response to the Iodoform test. It indicates absence of methyl keto group. 

Hence, n-amyl alcohol and 2-Pentanone are ruled out.

It gives negative response to the Tollen's test. It indicates the absence of the aldehyde group.

Hence, pentanal is ruled out.

IT produces n-Pentane on reduction. This indicates the presence of 5-carbon backbone. 

So, we can infer that the compound 'X' is 3-Pentanone.