An unknown salt is either \(\mathrm{NaF}, \mathrm{NaCl}\), or \(\mathrm{NaOCl}\). When 0.050 mol of the salt is dissolved in water to form 0.500 L of solution, the pH of the solution is 8.08 . What is the identity of the salt?

Short Answer

Expert verified
The identity of the unknown salt is \(\mathrm{NaOCl}\), based on the given pH of 8.08, the calculated concentration of hydroxide ions, and the reasonable concentration of \(\mathrm{OCl}^-\) in the solution.

Step by step solution

01

Calculate the hydrogen ion concentration from the given pH

Given the pH of the solution is 8.08, we can calculate the concentration of hydrogen ions ([\(\mathrm{H}^+\)]), using the formula: \[\mathrm{pH} = -\log_{10} [\mathrm{H}^+]\] The concentration of hydrogen ions is: \[[\mathrm{H}^+] = 10^{-\mathrm{pH}}\] Plugging in the given pH value: \[[\mathrm{H}^+] = 10^{-8.08} \approx 8.3 \times 10^{-9} \, \mathrm{M}\]
02

Determine the hydroxide ion concentration

Now, let's find the concentration of hydroxide ions ([\(\mathrm{OH}^-\)]). We'll use the ion product of water, \(K_w\), which is: \[K_w = [\mathrm{H}^+] [\mathrm{OH}^-] = 1.0 \times 10^{-14}\] We can solve for [\(\mathrm{OH}^-\)]: \[[\mathrm{OH}^-] = \frac{K_w}{[\mathrm{H}^+]} = \frac{1.0 \times 10^{-14}}{8.3 \times 10^{-9}} \approx 1.2 \times 10^{-6}\, \mathrm{M}\]
03

Calculate the concentration of the anions

Now we move on to calculating the concentration of the anions. We'll look at the salts one by one: 1. For \(\mathrm{NaF}\): Dissociation: \(\mathrm{NaF} \rightarrow \mathrm{Na}^+ + \mathrm{F}^-\) Here, the anion is \(\mathrm{F}^-\), so: \[[\mathrm{F}^-] = \frac{[\mathrm{OH}^-]}{[\mathrm{H}^+]} = \frac{1.2 \times 10^{-6}}{8.3 \times 10^{-9}} \approx 144\] 2. For \(\mathrm{NaCl}\): Dissociation: \(\mathrm{NaCl} \rightarrow \mathrm{Na}^+ + \mathrm{Cl}^-\) In this case, the chloride ion does not affect the pH of the solution, so we cannot determine the anion concentration for this salt based on the pH. 3. For \(\mathrm{NaOCl}\): Dissociation: \(\mathrm{NaOCl} \rightarrow \mathrm{Na}^+ + \mathrm{OCl}^-\) In this case, the anion is \(\mathrm{OCl}^-\), so: \[[\mathrm{OCl}^-] = \frac{[\mathrm{OH}^-]}{[\mathrm{H}^+]} = \frac{1.2 \times 10^{-6}}{8.3 \times 10^{-9}} \approx 144\]
04

Identify the salt

Based on the calculations, we can make the following observations: 1. For \(\mathrm{NaF}\), the concentration of \(\mathrm{F}^-\) is very high, which means it would have a much lower pH. So, this salt is not the one we are looking for. 2. For \(\mathrm{NaCl}\), the solution would be neutral, with a pH close to 7, as chloride ions do not affect the pH. Therefore, this salt is also not the one we are looking for. 3. For \(\mathrm{NaOCl}\), the calculated concentration of \(\mathrm{OCl}^-\) seems reasonable as it stabilized at a pH of 8.08. Thus, considering these observations, we can conclude that the identity of the unknown salt is \(\mathrm{NaOCl}\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Which of the following statements is false? (a) An Arrhenius base increases the concentration of \(\mathrm{OH}^{-}\) in water. (b) A Brønsted-Lowry base is a proton acceptor. (c) Water can act as a Brønsted-Lowry acid. (d) Water can act as a Brønsted-Lowry base. (e) Any compound that contains an -OH group acts as a Brønsted-Lowry base.

Benzoic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\right)\) and aniline \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\right)\) are both derivatives of benzene. Benzoic acid is an acid with $K_{a}=6.3 \times 10^{-5}\( and aniline is a base with \)K_{a}=4.3 \times 10^{-10}$ (a) What are the conjugate base of benzoic acid and the conjugate acid of aniline? (b) Anilinium chloride $\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}\right)$ is a strong electrolyte that dissociates into anilinium ions \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{3}^{+}\right)\) and chloride ions. Which will be more acidic, a \(0.10 \mathrm{M}\) solution of benzoic acid or a 0.10 \(M\) solution of anilinium chloride? (c) What is the value of the equilibrium constant for the following equilibrium?

The following observations are made about a diprotic acid $\mathrm{H}_{2} \mathrm{~A}:\( (i) \)\mathrm{A} 0.10 \mathrm{M}\( solution of \)\mathrm{H}_{2} \mathrm{~A}\( has \)\mathrm{pH}=3.30\(. (ii) \)\mathrm{A} 0.10 \mathrm{M}$ solution of the salt NaHA is acidic. Which of the following could be the value of \(\mathrm{p} K_{a 2}\) for \(\mathrm{H}_{2} \mathrm{~A}\) : (i) 3.22 , (ii) 5.30 , (iii) \(7.47,\) or (iv) \(9.82 ?\)

The volume of an adult's stomach ranges from about 50 \(\mathrm{mL}\) when empty to \(1 \mathrm{~L}\) when full. If the stomach volume is \(400 \mathrm{~mL}\) and its contents have a pH of 2 , how many moles of \(\mathrm{H}^{+}\) does the stomach contain? Assuming that all the \(\mathrm{H}^{+}\) comes from \(\mathrm{HCl}\), how many grams of sodium hydrogen carbonate will totally neutralize the stomach acid?

Calculate \(\left[\mathrm{H}^{+}\right]\) for each of the following solutions, and indicate whether the solution is acidic, basic, or neutral: (a) $\left[\mathrm{OH}^{-}\right]=7.3 \times 10^{-10} \mathrm{M}(\mathbf{b})\left[\mathrm{OH}^{-}\right]=0.015 \mathrm{M} ;$ (c) a solution in which \(\left[\mathrm{H}^{+}\right]\) is 10 times greater than \(\left[\mathrm{OH}^{-}\right]\).

See all solutions

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free