Solve the problem.
-Find the hydrogen ion concentration of a solution [ $\left. \mathrm { H } ^ { + } \right]$whose $\mathrm { pH }$ is $7.5$. Use the formula $\mathrm { pH } = - \log \left[ \mathrm { H } ^ { + } \right]$.
A) $3.16 \times 10 ^ { 7 }$ moles per liter
B) $- 8.75 \times 10 ^ { - 1 }$ moles per liter
C) $3.16 \times 10 ^ { - 8 }$ moles per liter
D) $8.75 \times 10 ^ { - 1 }$ moles per liter

Question

Quizplus · Accepted Answer

We are given $\mathrm { pH } = 7.5$.
Using the formula $\mathrm { pH } = - \log \left[ \mathrm { H } ^ { + } \right]$, we get 
$$7.5 = - \log \left[ \mathrm { H } ^ { + } \right]$$
Taking antilogarithm on both sides, we get
$$\left[ \mathrm { H } ^ { + } \right] = 3.16 \times 10 ^ { - 8 }$$
Therefore, the hydrogen ion concentration of the solution is $3.16 \times 10 ^ { - 8 }$ moles per liter. Hence, the correct answer is C.

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