24. What is the pH of a solution that results from diluting 0.20 mol nitrous aci

Question

24. What is the pH of a solution that results from diluting 0.20 mol nitrous acid (HNO2) and 0.50 mol sodium nitrite (NaNO2) with water to a volume of 2.0 L? (Ka of HNO2 = 4.5 x 10-4) 25. Each of the following mixtures can produce an effective buffer solution EXCEPT a. HF and KF b. NaH2PO4 and Na3PO4. c. NaHCO3 and Na2CO3. d. NaH2PO4 and Na2HPO4. e. HNO2 and NaNO2 26. If the ratio of base to acid in a buffer decreases by a factor of 100, how does the the pH of the buffer change? 27. The concentration of Ba2+ in an aqueous solution is 5.5 × 10-3 M. What concentration of CO32 is required to begin precipitating BaCOs? The Ksp of BaCO3 is 2.58 x 109 28. The solution contained 3.20 x 105 M of AgNOs When KCI was added to the solution up to 5.63 x 10 M, the precipitation of AgCI was observed. What is the Ksp of AgCI according to these data? Show your work.

Explanation / Answer

24) According to Henderson-hasselbalch equation,

pH = pKa + log [salt] /[acid]

pka = - log Ka = - log (4.5 x 10 -4) = 3.35

given that,

voulme = 2L

moles of NaNO2 = 0.50 mol

moles of HNO2 = 0.20 mol

hence, [HNO2] = 0.20 mol / 2 L = 0.10M

[NaNO2 ] = 0.50 mol / 2L = 0.25M

Hence, pH = 3.35 + log (0.25 / 0.10) = 3.35 + 0.398 = 3.748

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