Hydration of which alkyne with dilute $\mathrm{H}{}_2\mathrm{SO}{}_4$ / $\mathrm{HgSO}{}_4$ gives a mixture of two isomeric ketones?

Pent-2-yne is unsymmetrical with both triple-bond carbons internal and no strong electronic bias, so water adds either way to give pentan-2-one and pentan-3-one. Hex-3-yne and but-2-yne are symmetrical (one ketone each), and pent-1-yne follows Markovnikov addition to give only pentan-2-one.