for the following, mix the equal volumes of one solution from group I with one solution from group II to achieve the indicated pH. calculate the pH of each solution.
Group I: .2M NH4Cl, .2M HCl, .2M C6H5NH3Cl, .2M (C2H5)3NHCl
Group II: .2M KOI, .2M NaCN, .2M KOCl, .2M NaNO2
a. The solution with the lowest pH
b. The solution with the highest pH
c. The solution with the pH closest to 7
To calculate the pH of each solution, we can use the concept of acid-base reactions and the pH scale. The pH scale is a measure of the acidity or basicity of a solution. pH values range from 0 to 14, where values below 7 indicate acidity, values above 7 indicate basicity, and a pH of 7 is neutral.
When mixing an acid (Group I) with a base (Group II) to achieve a specific pH, we need to consider the nature of the acid and base being mixed. To determine the pH of each solution in groups I and II, we will look at the dissociation of the acid and the base, and their contribution to the overall pH.
Let's go through each solution and calculate the pH:
Group I:
1. NH4Cl: When NH4Cl dissolves in water, it dissociates into NH4+ and Cl-. NH4+ can act as a weak acid and donate a proton (H+) in water. The Cl- ion does not contribute to acidity. We need to find out the pH of NH4+.
2. HCl: HCl is a strong acid. It completely dissociates into H+ and Cl- ions in water. This means all the HCl will contribute to acidity.
3. C6H5NH3Cl: C6H5NH3Cl is a salt formed by the reaction of an aromatic amine (C6H5NH2) and HCl. The C6H5NH3+ ion can act as a weak acid and donate a proton (H+) in water. The Cl- ion does not contribute to acidity.
4. (C2H5)3NHCl: (C2H5)3NHCl is a salt formed by the reaction of a tertiary amine ((C2H5)3N) and HCl. The (C2H5)3NH+ ion can act as a weak acid and donate a proton (H+) in water. The Cl- ion does not contribute to acidity.
Group II:
1. KOI: KOI is a neutral compound, and it does not dissociate into H+ or OH- ions. It will not contribute to acidity or basicity.
2. NaCN: NaCN is a salt formed by the reaction of sodium hydroxide (NaOH) and hydrocyanic acid (HCN). NaCN dissociates into Na+ and CN- ions. The CN- ion can act as a weak base by accepting a proton (H+) in water. The Na+ ion does not contribute to basicity.
3. KOCl: KOCl is a neutral compound, and it does not dissociate into H+ or OH- ions. It will not contribute to acidity or basicity.
4. NaNO2: NaNO2 is a salt formed by the reaction of sodium hydroxide (NaOH) and nitrous acid (HNO2). NaNO2 dissociates into Na+ and NO2- ions. The NO2- ion can act as a weak base by accepting a proton (H+) in water. The Na+ ion does not contribute to basicity.
Now let's analyze each solution and determine their pH:
a. The solution with the lowest pH:
To find the solution with the lowest pH, we look for the strongest acid in Group I. Based on the provided information, HCl is a strong acid, meaning it will fully dissociate in water and contribute the most H+ ions. Therefore, the solution with HCl will have the lowest pH.
b. The solution with the highest pH:
To find the solution with the highest pH, we look for the strongest base in Group II. Based on the provided information, NaCN contains the CN- ion, which can act as a weak base by accepting H+ ions in water. Therefore, the solution with NaCN will have the highest pH.
c. The solution with the pH closest to 7:
To find the solution with the pH closest to 7, we need to consider which acid-base combination will neutralize each other most effectively. The combination of a strong acid (HCl from Group I) and a strong base (KOI from Group II) will most likely produce a solution closest to pH 7. Therefore, the solution with HCl from Group I and KOI from Group II will have the pH closest to 7.
By analyzing the nature of the acids and bases in groups I and II and considering their dissociation and contribution to acidity/basicity, we can determine the pH of each solution and answer the questions.