To 1 L of 1.0 M impure H₂SO₄ sample, 1.0 M NaOH solution was added and a plot was obtained as follows:

The % purity of H₂SO₄ and the slope of curve, respectively, are:

Moles of NaOH present in 1.0 M of NaOH is calculated as:

$\begin{array}{ccc}\mathrm{Molarity}& =& \frac{\mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} \mathrm{NaOH}}{\mathrm{Volume} (\mathrm{in} \mathrm{L})}\\ 1.0 \mathrm{M}& =& \frac{\mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} \mathrm{NaOH}}{1.5 \mathrm{L}}\\ \mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} \mathrm{NaOH}& =& 1.5 \mathrm{mol}\end{array}$

Number of moles of H₂SO₄ present in 1.0 M of H₂SO₄ is calculated as:

$\begin{array}{ccc}\mathrm{Molarity}& =& \frac{\mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} {\mathrm{H}}_2{\mathrm{SO}}_4}{\mathrm{Volume} (\mathrm{in} \mathrm{L})}\\ 1.0 \mathrm{M}& =& \frac{\mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} {\mathrm{H}}_2{\mathrm{SO}}_4}{1 \mathrm{L}}\\ \mathrm{Number} \mathrm{of} \mathrm{moles} \mathrm{of} {\mathrm{H}}_2{\mathrm{SO}}_4& =& 1.0 \mathrm{mol}\end{array}$

Reaction of NaOH and H₂SO₄ is:

$2\mathrm{NaOH}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}$

Above reaction states that 2 mol of NaOH requires to react with one mole of H₂SO₄. Number of moles of H₂SO₄ reacts with 1.5 mol of NaOH.

$\begin{array}{ccc}2 \mathrm{mol} \mathrm{NaOH}& =& 1 \mathrm{mol} {\mathrm{H}}_2{\mathrm{SO}}_4\\ 1.5 \mathrm{mol} \mathrm{NaOH}& =& 1.5 \mathrm{NaOH}\times \frac{1 \mathrm{mol} {\mathrm{H}}_2{\mathrm{SO}}_4}{2 \mathrm{mol} \mathrm{NaOH}}\\ & =& 0.75 \mathrm{mol} {\mathrm{H}}_2{\mathrm{SO}}_4\end{array}$

Total number of moles of H₂SO₄ is 1 but utilize only 0.75. Therefore, the % purity of H₂SO₄ is calculated as:

$\begin{array}{ccc}\% \mathrm{purity}& =& \frac{\mathrm{moles} \mathrm{of} {\mathrm{H}}_2{\mathrm{SO}}_4 \mathrm{react}}{\mathrm{total} \mathrm{moles} \mathrm{of} {\mathrm{H}}_2{\mathrm{SO}}_4}\times 100\\ & =& \frac{0.75 \mathrm{mol}}{1 \mathrm{mol}}\times 100\\ & =& 75\%\end{array}$

Formula of slope is:

$\mathrm{Slope}=\frac{{\mathrm{y}}_2-{\mathrm{y}}_1}{{\mathrm{x}}_2-{\mathrm{x}}_1}$

Substitute 0 as y₂, 1.5 as y₁, 1.5 as x₂ and 0 as x₁.

$\begin{array}{ccc}\mathrm{Slope}& =& \frac{0-1.5}{1.5-0}\\ & =& -1\end{array}$