Specific gravity (density) =1.54g/cc.
Volume =1L=1000ml
Mass of solution =1.54×1000
=1540g
purity of H3PO4 is 70
So weight of H3PO4=0.7×1540=1078g
Mole of H3PO4=molarmassmass=981078=11
Molarity= VolumeofsolutioninLNo.ofmolesofsolute
Molarity =1L11=11M