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Mixtures of weak acids and bases

38 questions on Mixtures of weak acids and bases from the Ionic Equilibrium II chapter: 7 NEET level, 16 JEE Main, 15 JEE Advanced. Each one opens with its answer and solution.

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Which of the following mixtures (equal volumes of 0.1 M solutions) forms an acidic buffer? NEET level
A solution is 0.10 M in a weak acid HA (K_a = 4.0 x 10^-6) and 0.10 M in a weak acid HB (K_a = 1.0 x 10^-6). Use [H+] = sqrtK_a1c_1 + K_a2c_2. The pH is closest... NEET level
Ammonium formate is the salt of a weak acid (HCOOH, pK_a = 3.75) and a weak base (NH3, pK_b = 4.75). Use pH = 7 + tfrac12(pK_a - pK_b). The pH of its aqueous so... NEET level
50 mL of 0.20 M CH3COOH is mixed with 30 mL of 0.10 M NaOH. Given pK_a = 4.76, log 3 = 0.477 and log 7 = 0.845, the pH is JEE Main level
A solution is 0.100 M in NH3 (K_b = 1.8 x 10^-5) and 1.00 x 10^-3 M in NaOH. Find the pH, using the exact quadratic for the ionisation of NH3 (no approximation ... JEE Main level
A solution is 1.00 x 10^-3 M in HCl and 0.100 M in CH3COOH (K_a = 1.8 x 10^-5). Using the exact quadratic for the ionisation of acetic acid, the pH is JEE Main level
100 mL of 0.10 M Na2CO3 is mixed with 60 mL of 0.10 M HCl. For HCO3-, pK_a2 = 10.33. With log 2 = 0.301 and log 3 = 0.477, the pH of the resulting solution is JEE Main level
A solution contains 0.10 M NH3 (K_b = 1.8 x 10^-5) and 0.10 M CH3NH2 (K_b = 4.4 x 10^-4). Use [OH-] = sqrtK_b1c_1 + K_b2c_2 and K_w = 1.0 x 10^-14. Find the pH ... JEE Main level
What is the degree of ionisation of 0.100 M CH3COOH (K_a = 1.8 x 10^-5) in a solution that is also 0.0500 M in HCl? Use the exact quadratic. Give alpha x 10^3 t... JEE Main level
100 mL of 0.20 M NH3 is mixed with 50 mL of 0.15 M HCl. For NH3, K_b = 1.8 x 10^-5 (pK_b = 4.745). Find the pH of the mixture (two decimals). JEE Main level
A solution is 0.10 M in CH3COOH and 0.10 M in CH3COONa (pK_a = 4.74). Assume volume changes on adding solids or gas are negligible. Select the correct statement... JEE Main level
A mixture is prepared from 50 mL of 0.10 M HCl and 50 mL of 0.10 M CH3COOH (pK_a = 4.74). It is then treated with 70 mL of 0.10 M NaOH. With log 2 = 0.301 and l... JEE Advanced level
100 mL of 0.30 M NH3 is mixed with 100 mL of 0.20 M CH3COOH. Given K_b(NH3) = 1.8 x 10^-5 (pK_b = 4.74), K_a(CH3COOH) = 1.8 x 10^-5 and log 2 = 0.301, the pH is... JEE Advanced level
A solution is 0.10 M in CH3COOH (K_a = 1.8 x 10^-5) and 0.10 M in HCN (K_a = 6.2 x 10^-10). Find [CN-] in the solution (in M). Neglect the dissociation of water... JEE Advanced level
100 mL of a solution that is 0.040 M in HCl and 0.060 M in CH3COOH (pK_a = 4.74) is titrated with 0.10 M NaOH. What total volume of NaOH (in mL, nearest integer... JEE Advanced level
50 mL of 0.10 M H3PO4 is mixed with 80 mL of 0.10 M NaOH. Given pK_a1 = 2.15, pK_a2 = 7.21, pK_a3 = 12.32, find the pH (two decimals). Take log 2 = 0.301, log 3... JEE Advanced level
What volume of 0.10 M HCl (in mL, nearest integer) must be added to 100 mL of 0.15 M NH3 to obtain a solution of pH 9.00? pK_b(NH3) = 4.74, K_w = 1.0 x 10^-14. ... JEE Advanced level
50 mL of 0.10 M HCl is mixed with 50 mL of 0.10 M CH3COOH (K_a = 1.8 x 10^-5) and titrated with 0.10 M NaOH. Neglect the ionisation of water; where only the wea... JEE Advanced level
A 0.10 M solution of ammonium formate, HCOONH4, is prepared. Take K_a(HCOOH) = 1.8 x 10^-4 (pK_a = 3.75), K_b(NH3) = 1.8 x 10^-5 (pK_b = 4.75) and K_w = 1.0 x 1... JEE Advanced level
A solution is 0.1 M in HCl and 0.1 M in CH3COOH (K_a = 1.8x10^-5). Its pH is approximately NEET level
50 mL of 0.2 M CH3COOH is mixed with 50 mL of 0.1 M NaOH. Given pK_a of acetic acid = 4.74, the pH of the mixture is NEET level
What is the approximate pH of a solution that is 0.1 M in NaOH and 0.1 M in NH3 (K_b = 1.8x10^-5)? NEET level
A solution contains 0.1 M HA (K_a = 4.0x10^-6) and 0.1 M HB (K_a = 6.0x10^-6). Using [H+] = sqrtK_1C_1 + K_2C_2, the pH is NEET level
A solution is 0.10 M in CH3COOH (K_a = 1.8x10^-5) and 0.10 M in HCOOH (K_a = 1.8x10^-4). Using [H+] = sqrtK_1C_1+K_2C_2, find the pH (two decimals). JEE Main level
40 mL of 0.20 M NH3 is mixed with 30 mL of 0.10 M HCl. Given pK_b(NH3) = 4.74 and log 2 = 0.301, log 3 = 0.477, the pH is JEE Main level
A solution is 0.25 M in HCl and 0.050 M in a weak acid HA (K_a = 3.0x10^-5). Assuming [H+] approx 0.25 M, find the degree of dissociation of HA in units of 10^-... JEE Main level
A buffer is 0.10 M in CH3COOH and 0.10 M in CH3COONa (pK_a = 4.74). Select the correct statement(s). JEE Main level
100 mL of 0.15 M NaOH is added to 250 mL of 0.10 M HCOOH (pK_a = 3.75). Using log 2 = 0.301 and log 3 = 0.477, the pH is JEE Main level
A solution contains 0.100 M NH3 (K_b = 1.8x10^-5) and 0.0500 M NaOH. Solve the ammonia equilibrium exactly for the extra OH- it supplies, then find the pH (two ... JEE Main level
Equal volumes of 0.10 M CH3COOH (pK_a = 4.76) and 0.10 M NH3 (pK_b = 4.74) are mixed. Using pH = 7 + tfrac12(pK_a - pK_b) for the salt of a weak acid and a weak... JEE Main level
A solution is prepared that is 0.20 M in Na2CO3 and 0.10 M in NaHCO3. Given pK_a2(H2CO3) = 10.33 and log 2 = 0.301, its pH is JEE Main level
50 mL of 0.30 M NH4Cl is mixed with 30 mL of 0.20 M NaOH. Given pK_b(NH3) = 4.74, log 2 = 0.301 and log 3 = 0.477, the pH of the mixture is JEE Advanced level
A solution is 0.10 M in CH3COOH (K_a = 1.8x10^-5) and 0.10 M in HCN (K_a = 6.2x10^-10). The concentration of CN- is JEE Advanced level
100 mL of 0.20 M Na2CO3 is mixed with 150 mL of 0.10 M HCl. Given pK_a2(H2CO3) = 10.33 and log 3 = 0.477, the pH is JEE Advanced level
A solution is 0.10 M in NH3 (K_b = 1.8x10^-5) and 0.10 M in CH3NH2 (K_b = 4.5x10^-4). Using [OH-] = sqrtK_1C_1+K_2C_2, the concentration of NH4+ is JEE Advanced level
A solution contains 0.10 M HA (K_a = 2.0x10^-5) and 0.050 M NaA. Without volume change, 0.020 mol L^-1 of HCl is then added. Using log 2 = 0.301, the pH is JEE Advanced level
Take pK_a(CH3COOH) = 4.74 and pK_b(NH3) = 4.74. Which of the following mixtures give a solution with the pH stated? JEE Advanced level
A solution is 0.10 M in HA (K_a = 2.0x10^-4) and 0.10 M in HB (K_a = 5.0x10^-6). Using [H+] = sqrtK_AC_A + K_BC_B, select the correct statement(s). JEE Advanced level