Answer
a) $C_5H_4$
b) $C_{10}H_8$
Work Step by Step
a) Number of moles of $CO_2$:
$1.0620\ g\div 44.001\ g/mol=0.0241\ mol$
$0.0241\ mol$ of C
Number of moles of $H_2O$:
$0.1739\ g\div 18.015\ g/mol=0.00965?\ mol$
$0.0193\ mol$ of H
H/C Ratio: $0.80=4/5$
Empirical formula:
$C_5H_4$
b) Molar mass of the empirical formula: $64.085\ g/mol$
$128.2/64.085=2.00$
Molecular formula:
$C_{10}H_8$