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A container of antibiotic is labeled \"tetracycline hydrochloride\". This means

ID: 514023 • Letter: A

Question

A container of antibiotic is labeled "tetracycline hydrochloride". This means A. this particular preparation of tetracycline is very acidic. B. tetracycline contains an amine group that has been protonated, and chloride is the counterion. C. tetracycline contains a carboxyl group that has been protonated, and chloride is the counterion. D. tetracycline contains a chlorine atom that has been protonated. E. the pills will not dissolve well in water. At the equivalence point in the titration of an acid with a base. A. the [H_3 O^+] equals the K_a of the acid. B. the [H_3 O^+] equals the K_a of the indicator. C. the number of moles of added base equals the number of moles of acid originally present. D. the pH is 7.0. E. the pH has reached a maximum. When a weak base is titrated with a strong acid, the pH at the equivalence point A. is greater than 7.0. B. is equal to 7.0. C. is less than 7.0. D. is equal to the pK_ of the acid. E. is equal to 14.0 - pK_ where pk_ is that of the conjugate base of the weak acid. Which of the following substances has the smallest solubility in water? A. Pbl_2, K_sp = 7.9 times 10^-9 B. BaF_2, K_sp = 1.5 times 10^-6 C. Ca(OH)_2, K_sp = 6.5 times 10^-6 D. Zn(IO_3)_2, K_sp = 3.9 times 10^-6 E. Ag_2 SO_4, K_sp = 1.5 times 10^-5 0.20 mol of NaF is added to 1.00 L of 0.35 M cadmium nitrate cd(NO_3)_2. Which of the following statements is correct? K_sp = 6.44 times 10^-3 for CdF_3 A. Cadmium fluoride precipitates. B. The solution is unsaturated and no precipitate forms. C. The solubility of cadmium fluoride is increased by the presence of additional fluoride ions. D. One must know K_sp for cadmium nitrate to make predictions on this system. E. The presence of NaF will raise the solubility of Cd(NO_3)_2. Which of the following would be expected to be more soluble in acid than in neutral water? A. CaF_2 B. CaCl_2 C. CaBr_2 D. Cal_2 E. none of these

Explanation / Answer

6. A container of antibiotic is labeled " Tetracycline Hydrochloride".This means tetracycline contains a chlorine atom that has been protonated. As per the structure of Tetracycline Hydrochloride, the amine or carboxylic group is not protonated but chlorine atom is protonated

7. At the equivalence point of titration of an acid with base, the number of moles of added base equals the number of moles of acid originally present. This is the definition of equivalence point.

8. When a weak base is titrated with a strong acid, the pH at equivalence point is less than 7. At the equivalence point, the solution only has ions of conjugate acid of a weak base and the conjugate acid is strong for a weak base. So when this conjugate acid will come i contact with H2O it will form hydronium ions again making the solution acidic and thus pH will be less than 7

9. PbI2 has the smallest solubility in water. Since all the substance dissociate in water to give same number of ions (3) so their solubility can directly be compared with their solubility product and the substance with lowest solubility product is the has the smallest solubility in water.

10. NaF dissociates to give 0.2 mol of Na+ and F- and 1 litre solution of 0.35 M Cd(NO3)2 will give 0.35 moles of Cd+ and 0.70 moles of NO3- in 1 litre solution. [Cd+] = 0.35 mol/1 litre = 0.35, [F-] = 0.20 mol/1 litre = 0.20

Solubility, Q = [Cd+][F-]2

Q = [0.35][0.20]2

Q = 0.014
which is greater than the Ksp of 6.44 × 10-3

Thus,answer is
a. Cadmium fluoride precipitates

11. CaF2 is the least soluble in water and most soluble in acid among all the salts present.

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