I GOT THIS WRONG IN AN ASSIGNMENT. I HAVE AN EXAM IN 2 DAYS. CAN YOU SHOW ME HOW TO DO IT PLS.
What is the pH of a 2.62 x 10 -1 M NaNO2 solution ? NB the pKa for HNO2 = 3.153.
12.13
13.42
1.87
8.29
0.58
NaNO2 is the salt of a strong base (NaOH) and a weak acid (HNO2). The NO2^- is hydrolyzed.
NO2^- + HOH ==> HNO2 + OH^-
Kb = (Kw/Ka) = (HNO2)(OH^-)/(NO2^-)
Set up an ICE chart.
You know Kw. You can calculate Ka from pKa. (HNO2) will be x. (OH^-) will be x. (NO2^-) = 0.262. Solve for x, convert to pOH, then to pH. I found pH = 8.285 which I would round to 8.28 but I would pick the 8.29 for the answer.
To find the pH of a solution, you need to use the equation for calculating the pH of a weak acid. In this case, NaNO2 is a salt of a weak acid (HNO2), so you need to consider the dissociation of the weak acid.
The dissociation equation for HNO2 is:
HNO2 ⇌ H+ + NO2-
Since only the acid is weak, you can assume that it fully dissociates into H+ and NO2-. As a result, the concentration of H+ will be equal to the concentration of HNO2.
First, calculate the pKa of the weak acid using the formula pKa = -log(Ka). In this case, pKa = 3.153.
Next, use the pKa value to find the Ka value using the equation Ka = 10^(-pKa). Therefore, Ka = 10^(-3.153).
Now, apply the equation for converting Ka to the concentrations of H+ and HNO2. Ka = [H+][NO2-] / [HNO2].
Since the stoichiometric coefficient for HNO2 is 1, we know that [HNO2] = 2.62 x 10^(-1) M.
Now, we can rearrange the equation to solve for [H+]: [H+] = (Ka * [HNO2]) / [NO2-].
The concentration of NO2- is equal to the concentration of NaNO2. So [NO2-] = 2.62 x 10^(-1) M.
Plug in the values and solve for [H+].
[H+] = (10^(-3.153) * (2.62 x 10^(-1))) / (2.62 x 10^(-1))
Simplifying the equation, [H+] = 10^(-3.153).
Finally, take the negative logarithm of the [H+] value to find the pH of the solution.
pH = -log([H+])
Use a calculator to evaluate -log(10^(-3.153)) to find the pH.
The correct pH value for the solution will be one of the options provided (12.13, 13.42, 1.87, 8.29, or 0.58).