Choose the correct ranking based on acid strength for these three acids. Each pi
ID: 529272 • Letter: C
Question
Choose the correct ranking based on acid strength for these three acids. Each picture is a representation of an ionized acid that is dissolved in water. The water molecules are not included in the pictures for the sake of clarity. (A) HY > HX > HZ (B) HY > HZ > HX (C) HZ > HY > HX (D) HZ > HX > HY A one liter solution contains 0.200 M CH_3COOH (K = 1.8 times 10^-5) and 0.200 M CH_3COONa The initial pH is 4.74. Calculate the pH when 0.0500 mole of HCl is added to the solution. (A) 4.96 (B) 4.74 (C) 4.52 (D) 4.23 Ten millimeters of 0.10 M ammonium chloride is titrated with 0.10 M sodium hydroxide, The titration curve is shown. What is the approximate pK of the ammonium ion? (A) 12.0 (B) 10.5 (C) 9.0 (D) 7.2 What is the conjugate base of H_2PO^-_4? (A) PO^2-_3 (B) Po^2-_4 (C) H_3PO_4 (D) HPO^2-_4 Which statement is true about the pH of an aqueous solution? (A) As pH increases, pK_w increases. (B) As pH increases, pK_w decreases. (C) As pH increases, hydroxide ion concentration increases. (D) As pH increases, hydronium ion concentration increases. At 50 degree C, pK_w = 13.26. What is the pH of pure water at this temperature? (A) 13.26 (B) 7.37 (C) 7.00 (D) 6.6.3 Which is a Lewis acid-base reaction, but not a Bronsted-Lowry acid-base reaction? (A) NH_2(g) + BF_3(g) rightarrow H_3NBF_3(g) (B) NH_2(g) + H_2O(l) rightarrow NH _4(aq) + OH^-(aq) (C) CH_3NH_2(aq) + HBr(aq) rightarrow CH_3NH^2_3(aq) + Br^-(aq) (D) CH_3COOH(aq) + H_2O(l) rightarrow CH_3COO^-(aq) + H_2O^-(aq) The K_a, of a weak acid is l 8 times 10^-4. What is the K_a of its conjugate base? (A) 1.8 times 10^10 (B) 5.6 times 10^3 (C) 18 times 10^-4 D) 5.6 times 10^-21 An aqueous buffer contains acetic acid (CH_3COOH) and sodium acetate (CH_3COONa). Which reaction shows how the buffer minimizes the pH change when HCI is added? (A) H^+(aq) + OH^-(aq) H_2O(l) (B) CH_3COO^-(aq) + H^=(aq) CH_3COOH(aq) (C) CH_3COOH (aq) + H^+(aq) CH_3COOH^+_2(aq) (D) CH_3COOH(aq) + OH^-(aq) CH_3COO^-(aq) + H_2O(l) Which is a correct statement of the third law of thermodynamics? (A) The energy of the universe is constant. (B) The entropy of the universe is constant. (C) The energy of a system is controlled by the entropy with of that system. (D) The entropy of a perfect is zero at zero k. Which has the highest standard molar entropy? (A) CH_4(g) (B) CH_3CH_2CH_3(g) (C) CH_3CH_2CH_3(l) (C) CH_3(CH_2)_2CH_3(g) Which is true for a spontaneous process? (A) The entropy of the universe always increases. (B) The entropy of the system always decreases. (C) The entropy of the system always increases. (D) The entropy of the system is equal and opposite to the entropy change of the surroundings. To cause the largest increase in entropy for one mole of an ideal gas. _____ the temperature and _____ the volume. (A) increase, increase (B) increase, decrease (C) decrease, increase (D) decrease, decreaseExplanation / Answer
(33)
HY > HX > HZ
SInce HY undergoes almost complete ionisation, where as HX undergoes partial ionisation but HZ is not ionised.
(34)
Addition of strong acid to the acid buffer will increease the concentration of acid bu decrease the concentration of salt.
New, [acid] = 0.200 + 0.0500 = 0.250 M
[Salt] = 0.200 - 0.0500 = 0.150 M
pKa = - LogKa = - Log(1.8 * 10-5) = 4.74
Formula to caluclate pH of acid buffer is,
pH = pKa + Log[salt]/[acid]
pH = 4.74 + Log(0.150 / 0.250)
pH = 4.52
(C)
(35) Form the graph the pKa of Ammonium ion is around,
(C) 9.0