chemistry help please 12. Formic acid (HCHO,) is a weak acid with Ka- 1.8x104. T
ID: 561752 • Letter: C
Question
chemistry help please
12. Formic acid (HCHO,) is a weak acid with Ka- 1.8x104. The plH of a buffer solution containing HCHO,/NaCHO, is 3.89, which of the following statements is TRUE? B) [HCHO] INaCHO] D) It is not possible to make a buffer of this phl from HCHO, and NaCHO Which of the following compounds will have the highest molar solubility in pure 13. A) Pb(IO)h, Ksp 1.5x 109 B) PbF2. Ksp 3.6x10 C) SrSO4, Ksp-3.2×10-7 ) No definite statement about molar solubility of these compounds can be made based on the information given. a slightly soluble salt. In presence of ammonia, Ni can form the complex NiNH) Based on these information, which of the following statements is correct? with K,- 14. Ni(OH) is 5.6x10. A) Ni(OD), is more soluble in ammonia than in pure water B) NitOH) has the same solubility in ammonia and in pure water. C) Ni(OH is less soluble in ammonia than in pure water D) No statements can be made about solubility of Ni(OH) based on the information given 15. What volume of water must be added to 20.0 mL of 0.10 M HCI so that its pH becomes l.30? A) 25. mL B) 40. mL C) 20. ml D) 50. ml 16. What is the pH at equivalence point for the titration curve shown below titrant A) pH 7 C) pH=7 D) pH 14Explanation / Answer
12 ) A
Pka = -log(ka) = 3.74
PH =HCHO2/ NaCHO2 = 3.89
pH = pKa + log [NaCHO2]/[HCHO2]
log [NaCHO2]/[HCHO2] = 3.89 - 3.74 = 0.15 which means NaCHO2 > HCHO2
13 ) C
why becuase solubilty = sqrt of ksp
so the one with more ksp will have more solubilty
14) A ) NiOH2 have more solubility in ammonia ore than in water
15) B
aply formua M1V1=M2V2
M2 = 10-ph
M1= 0.10M V1 = 20ml by calculating we get M2 = 0.050M
16 ) B
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