Calculate the number of hydrogen ions (H+) in 20.00 cm³ of a 0.04375 mol/dm³ H₂SO₄ solution.

Step 4: Calculate the number of hydrogen ions ($\text{H}^+$) in the volume of A used.
First, calculate the moles of $\text{H}_2\text{SO}_4$ used. We assumed the average volume of A used ($V_a$) is $20.00 \text{ cm}^3 = 0.02000 \text{ dm}^3$.

$$\text{Moles of H}_2\text{SO}_4 = \text{Concentration of A} \times \text{Volume of A}$$ $$\text{Moles of H}_2\text{SO}_4 = 0.04375 \text{ mol dm}^{-3} \times 0.02000 \text{ dm}^3$$ $$\text{Moles of H}_2\text{SO}_4 = 0.000875 \text{ mol}$$

Next, determine the moles of hydrogen ions. From the balanced dissociation equation of sulfuric acid:

\text{H}_2\text{SO}_{4(aq)} \rightarrow 2\text{H}^{+}_{(aq)} + \text{SO}_{4}^{2-}_{(aq)}

Each mole of $\text{H}_2\text{SO}_4$ produces 2 moles of $\text{H}^+$ ions.

$$\text{Moles of H}^+ = 2 \times \text{Moles of H}_2\text{SO}_4$$ $$\text{Moles of H}^+ = 2 \times 0.000875 \text{ mol} = 0.00175 \text{ mol}$$

Finally, calculate the number of hydrogen ions using Avogadro's number ($N_A = 6.022 \times 10^{23} \text{ mol}^{-1}$).

$$\text{Number of H}^+ \text{ ions} = \text{Moles of H}^+ \times N_A$$ $$\text{Number of H}^+ \text{ ions} = 0.00175 \text{ mol} \times 6.022 \times 10^{23} \text{ mol}^{-1}$$ $$\text{Number of H}^+ \text{ ions} = 1.05385 \times 10^{21}$$

Rounding