List the following in order of increasing pH of their 0.25 M solutions: NH4Cl, MgCl2, HCl, NaOCl, C6H5NH3Cl and NaClO2.
To determine the increasing pH of the 0.25 M solutions, we need to analyze the acidity/basicity of each compound.
First, let's understand some basic concepts:
- NH4Cl is an acidic salt since NH4+ ion can act as a weak acid in water.
- MgCl2 is a neutral salt since it does not undergo hydrolysis in water.
- HCl is a strong acid and fully ionizes in water, resulting in a highly acidic solution.
- NaOCl is a basic salt since OCl- ion can act as a weak base in water.
- C6H5NH3Cl is an acidic salt since C6H5NH3+ ion can act as a weak acid in water.
- NaClO2 is a basic salt since ClO2- ion can act as a weak base in water.
Based on these concepts, we can determine the increasing pH of the 0.25 M solutions as follows:
1. HCl - It is a strong acid, which means it will have the lowest pH.
2. NH4Cl - It is an acidic salt and will have a higher pH than HCl but lower than the remaining compounds.
3. C6H5NH3Cl - It is also an acidic salt and will have a higher pH than NH4Cl.
4. NaClO2 - It is a basic salt and will have a higher pH than C6H5NH3Cl.
5. NaOCl - It is also a basic salt and will have a higher pH than NaClO2.
6. MgCl2 - It is a neutral salt, so it will have the highest pH among all the compounds.
In summary, the compounds listed in order of increasing pH of their 0.25 M solutions are:
HCl < NH4Cl < C6H5NH3Cl < NaClO2 < NaOCl < MgCl2.
To determine the order of increasing pH for the given 0.25 M solutions, we need to consider the nature of their chemical species in water. Strong acids and bases tend to dissociate completely in water, while weak acids and bases show a partial dissociation. The degree of dissociation affects the concentration of hydrogen ions (H+) or hydroxide ions (OH-) in the solution, which determines pH.
Here's the step-by-step process to determine the order:
1. NH4Cl: Ammonium chloride (NH4Cl) is a salt formed from the weak base ammonia (NH3) and a strong acid, hydrochloric acid (HCl). Although the NH4+ ion acts as a weak acid, the Cl- ion doesn't affect pH. Therefore, NH4Cl's pH primarily depends on the weak acid property. Ammonium chloride will have a slightly acidic pH. So, let's place it in the middle of the order for now.
2. MgCl2: Magnesium chloride (MgCl2) is a salt formed from a strong base (magnesium hydroxide) and a strong acid (hydrochloric acid). Since both the cation (Mg2+) and the anion (Cl-) don't affect pH, the pH of MgCl2 primarily depends on the water dissociation of hydrochloric acid. HCl is a strong acid, giving rise to a high concentration of H+ ions. Thus, MgCl2 will have a lower pH than NH4Cl.
3. HCl: Hydrochloric acid (HCl) is a strong acid that dissociates completely in water to produce a high concentration of H+ ions. Therefore, HCl will have a lower pH than NH4Cl and MgCl2.
4. NaOCl: Sodium hypochlorite (NaOCl) is produced when chlorine gas reacts with sodium hydroxide solution. It is classified as a weak base since it partially dissociates in water to produce hydroxide ions (OH-). Consequently, NaOCl has a slightly alkaline pH compared to the previous three compounds.
5. C6H5NH3Cl: Phenylammonium chloride (C6H5NH3Cl) is a salt formed from a weak base (phenylamine) and a strong acid (hydrochloric acid). Similar to NH4Cl, C6H5NH3Cl will exhibit a slightly acidic pH due to the weak acid property of the ammonium ion. Hence, we'll place it after NH4Cl.
6. NaClO2: Sodium chlorite (NaClO2) is a salt that dissociates in water to produce chlorite ions (ClO2-). Since chlorite ions are weak bases, NaClO2 will have the highest pH among the given compounds.
Putting it all together, the order of increasing pH for the 0.25 M solutions is as follows:
HCl < MgCl2 < NH4Cl < C6H5NH3Cl < NaOCl < NaClO2
Six problems. Here is how you do the first one (NH4Cl). The pH of the solution is determinded by the hydrolysis of the NH4^+. Newer texts say the NH4^+ is a weak acid. (The Cl^- is a strong base and isn't hydrolyzed).
............NH4^+ + H2O ==> NH3 + H3O^+
I..........0.25M........................0.............0
C.............-x...........................x.............x
E............0.25-x..................... x.............x
Ka(for NH4^+) = Kw/Kb(for NH3) = (NH3)(H3O^+)/(NH4^+)
Kw is 1E-14; Kb for NH3 is 1.75E-5
(1E-14/1.75E-5) = (x)(x)/(0.25-x)
Solve for x = (H3O)^+ and convert to pH.
Post your work on any of these if you get stuck. Don't use my values of Ka and Kw but look these values up in your text.
For weak acids that hydrolyze, such as the OCl^- of NaOCl, those equations are similar to the following.
..............OCl^- + HOH ==> HOCl + OH^-
When you solve for x you will see that equals (OH^-) so you convert that to pOH, then use Kw = pH + pOH to find pH.