Question

The pH of the human blood is 7.4. This implies

• A. There are no ${\mathrm{H}}^{+}$ions in blood.
• B. The concentration of ${\mathrm{H}}^{+}$ions in blood is more than the concentration of ${\mathrm{OH}}^{-}$ions.
• C. The concentration of ${\mathrm{OH}}^{-}$ions in blood is slightly more than the concentration of ${\mathrm{H}}^{+}$ ions.
• D. The concentration of ${\mathrm{OH}}^{-}$ions in blood is significantly more than the concentration of ${\mathrm{H}}^{+}$ ions.

Answer 1

The correct option is C

The concentration of ${\mathrm{OH}}^{-}$ions in blood is slightly more than the concentration of ${\mathrm{H}}^{+}$ ions.

The explanation for the correct option:

• Our human blood has a normal pH range of $7.35\mathrm{to}7.45.$
• This means that blood is slightly alkaline or basic in nature. So the concentration of ${\mathrm{OH}}^{-}$ions in the blood is a bit more than the concentration of ${\mathrm{H}}^{+}$ ions.

The explanation for the incorrect options:

• (A) When the pH of the blood is given as 7.4. which means that

$$\begin{gathered} \left[{\mathrm{H}}^{+}\right]={10}^{-7.4} \\ \approx 4.0\times {10}^{-8}\mathrm{M} \end{gathered}$$, so the concentration of $\left[{\mathrm{H}}^{+}\right]$ is not equal to zero.

• (B) Our blood is slightly alkaline or basic in nature. So here is the concentration of ${\mathrm{OH}}^{-}$ions are more than that of the concentration of ${\mathrm{H}}^{+}$ ions, not the opposite.
• (D) Blood is slightly alkaline or basic in nature. So the concentration of ${\mathrm{OH}}^{-}$ions in the blood is a bit more than the concentration of ${\mathrm{H}}^{+}$ ions.

Hence, option (c) is correct. i.e., The pH of the human blood is 7.4. This implies that the concentration of ${\mathrm{OH}}^{-}$ions in the blood is moderately / slightly more than the concentration of ${\mathrm{H}}^{+}$ ions.