The problem states that 1 mL of the
H2O2 solution yields 20 mL of oxygen gas at STP. By definition, "
x volume"
H2O2 means that 1 mL of the solution produces
xmL of
O2 at STP. Therefore, the volume strength,
x, is 20 .
The decomposition of hydrogen peroxide is:
2H2O2→2H2O+O2From the stoichiometry, 2 moles of
H2O2(2×34g=68g) produce 1 mole of
O2(22.4L at STP).
If an
H2O2 solution has a volume strength of '
x ', it means
1L(1000mL) of the solution produces '
x ' L of
O2 at STP.
Mass of
H2O2 required to produce '
x ' L of
O2.
Mass of H2O2=(22.4LO268gH2O2)×(xLO2)=22.468xgThis mass of
H2O2 is present in 1000 mL of the solution.
The
(w/v)% is calculated as
(w/v)%= Volume of solution (mL) Mass of solute (g)×100(w/v)%=100022.468x×100(w/v)%=22.4×1068x=22468x=5617xBy substituting
x=20,(w/V)%=6.06%.