Answer
$0.0022\ g$
Work Step by Step
From Henry's Law:
$S=k_HP$
$S=1.3\times10^{-3}\ mol/kg.bar\times 40\ mmHg\times1\ bar/750.06\ mmHg=6.93\times10^{-5}\ mol/kg$
Assuming a density of 1 kg per liter:
$6.93\times10^{-5}\ mol/kg\times 1.0\ kg/L\times 1.0\ L\times 32.00\ g/mol=0.0022\ g$
