Question

A solution is made by dissolving 25.5 g of CH₃NH₃NO₃ in 500.0 mL of water.

a. Does CH₃NH₃⁺ have any acidic or basic properties?
b. Does NO3- have any acidic or basic properties?
c. Write the acidic equilibrium equation that exists in the solution.
d. What is the value of Ka for CH3NH3+? The Kb of CH3NH2 is 4.4 x 10^-4
e. Determine the pH of the solution.

Answer 1

CH₃NH₃⁺ has acidic properties in water, NO3- is neutral, the acidic equilibrium equation is CH₃NH₃⁺ + H₂O → CH₃NH₄⁺ + OH-, the value of Ka for CH₃NH₃⁺ is 2.3 × 10^-11, and the pH of the solution can be calculated using the concentration of [H₃O+].

Step-by-step explanation:

a. CH₃NH₃⁺ can act as a weak acid in water by donating a proton (H+). This is because it has a positive charge and can easily lose a hydrogen ion. Therefore, CH₃NH₃⁺ has acidic properties.

b. NO3- does not have any acidic or basic properties. It is a neutral ion.

c. The acidic equilibrium equation for CH₃NH₃⁺ in water is:

CH₃NH₃⁺ + H₂O → CH₃NH₄⁺ + OH-

d. To find the value of Ka for CH₃NH₃⁺, we can use the Kb of CH₃NH₂ and the equation:

Ka × Kb = Kw

Given that Kb for CH₃NH₂ is 4.4 × 10^-4, we can solve for Ka and find that its value is 2.3 × 10^-11.

e. To determine the pH of the solution, we need to consider the acidic equilibrium equation. After solving for Ka, we can use the equation:

pH = -log[H₃O+]

Substituting the concentration of [H₃O+] from the equation, we can calculate the pH of the solution.

Answer 2

a. CH₃NH₃⁺ has acidic properties because it can donate a proton. b. NO₃⁻ does not have acidic or basic properties. c. The acidic equilibrium equation for the solution is CH₃NH₃⁺ + H₂O ⇌ CH₃NH₂ + H₃O⁺. d. The value of Ka for CH₃NH₃⁺ is 2.27 × 10^-11. e. The pH of the solution can be calculated using the concentration of H₃O⁺ ions.

Step-by-step explanation:

a. CH₃NH₃⁺ has acidic properties because it can donate a proton (H⁺) in a chemical reaction. This is due to the presence of the methylammonium cation (CH₃NH₃⁺) in the solution.

b. NO₃⁻ does not have acidic or basic properties as it does not donate or accept protons. It is a neutral ion.

c. The acidic equilibrium equation for the solution is CH₃NH₃⁺ + H₂O ⇌ CH₃NH₂ + H₃O⁺.

d. To calculate the value of Ka for CH₃NH₃⁺, we need to use the relationship between Ka and Kb. The Kb for CH₃NH₂ is 4.4 × 10^-4, and since CH₃NH₃⁺ is the conjugate acid of CH₃NH₂, we can use the equation Kb × Ka = Kw (the ionization constant of water). Therefore, Ka = Kw/Kb = 1.0 × 10^-14 / 4.4 × 10^-4 = 2.27 × 10^-11.

e. To determine the pH of the solution, we need to consider the concentration of H₃O⁺ ions. Since CH₃NH₃⁺ is a weak acid and does not completely ionize, we need to calculate the concentration of H₃O⁺ ions using the equilibrium equation and then take the negative logarithm to find the pH. This calculation requires additional information such as the initial concentration of CH₃NH₃⁺ and its equilibrium concentration.