Question

the ph of a solution of hbr is 3.21 at 25°c. what is the h⁺ concentration in this solution?

Explanation:

Step1: Recall the pH formula

The formula for pH is \(pH = -\log[H^{+}]\). We can rearrange it to solve for \([H^{+}]\): \([H^{+}]=10^{-pH}\)

Step2: Substitute the given pH value

Given \(pH = 3.21\), substitute into the formula: \([H^{+}]=10^{- 3.21}\)

Step3: Calculate the value

Using the property \(a^{-b}=\frac{1}{a^{b}}\) and \(10^{-3.21}=10^{-(3 + 0.21)}=10^{-3}\times10^{-0.21}\). We know that \(10^{-3}=0.001\) and \(10^{-0.21}\approx0.617\) (since \(10^{-0.2}=\frac{1}{10^{0.2}}\approx0.631\) and \(10^{-0.21}\) is slightly less). So \(10^{-3.21}=10^{-3}\times10^{-0.21}\approx0.001\times0.617 = 6.17\times10^{-4}\)

Alternatively, using a calculator: \(10^{-3.21}=6.17\times 10^{-4}\space mol/L\)

Answer:

\(6.17\times 10^{-4}\space mol/L\)