The pH at the equivalence point of a titration of a weak base with a strong acid

Question

The pH at the equivalence point of a titration of a weak base with a strong acid will be greater than 7.00 equal to 7.00 less than 7.00 undeterminable Consider a solution of 2.0 M HCN and 1.0 M NaCN (K_a for HCN = 6.2 Times 10^-10), Which of the following statements is true? The solution is not a buffer because [HCN] is not equal to [CN^-]. The pH of the solution will be below 7.0. The buffer will be more resistant to pH changes from addition of strong acid than of strong base. [OH] > [H^+] What is the effective buffer range of a solution with 1.00 M HA)(K_d = 1 Times 10^-5) and 1.00 M NaA? 4 - 6 5 - 7 3 - 5 4.5 - 5.5 Which of the following solutions has the greatest buffering capacity? 0.50 M HC_2H_3O_2 and 0.50 M NaC_2H_3O_2 0.50 M HC_2H_3O_2 and 1.00 M NaC_2H_3O_2 1.00 M HC_2H_3O_2 and 0.50 M NaC_2H_3O_2 1.00 M HC_2H_3O_2 and 1.00 M NaC_2H_3O_2 Methyl orange is an indicator with a K_a of 1 Times 10^-5. Its acid form, HIn, is red, while its base form, In^+, is yellow. At pH = 5.0, the indicator will be orange red blue yellow The correct mathematical expression for finding the molar solubility (S) of Al_2S_2 is: 2S^3 = K_sp 108S^3 = K_sp 4S^3= K_sp 8S^3 = k_sp If [OH^-] = 3.64 Times 10^-4 M in a saturated solution of Mg(OH)_2, the K_sp of Mg(OH)_2 is: 6.5 Times 10^-8 4.7 Times 10^-11 1.3 Times 10^-7 2.4 Times 10^-11 Calculate the concentration of Al^3+ in a saturated aqueous solution of Al(OH)_3 (K_sp = 1.8 Times 10^-32). 5.1 Times 10^-9 M 1.7 Times 10^-34 M 1.2 Times 10^-8 M 6.7 Times 10^-5 M Given the solubility products, BaSO_4 K_sp: 1.5 Times 10^-9 1.3 Times 10^-8 5.0 Times 10^-8 M 1.6 Times 10^-9 Which of the following is the most soluble compound? BaSO_4 PbSO_4 AgBr BaCO_3 The best explanation for the dissolution of ZnS in dilute HCl is that: The sulfide-ion concentration is decreased by the formation of HS. the sulfide-ion concentration is decreased by oxidation to sulfur. the zinc-ion concentration is decreased by the formation of a chloro complex. The solubility product of ZnCl_2 is less than that of ZnS. If 30.0 mL of 5.00 Times 10^-4 M Ca(NO_3)_2 are added to 70.0 mL of 2.00 Times 10^-4 M NaF, will a precipitate occur? ((K_sp of CaF_2 = 4.0 Times 10^-11) No, because the ion product is greater than K_sp. Yes, because the ion product is less than K_sp. No, because the ion product is less than K_sp. Yes, because the ion product is greater than K_sp.

Explanation / Answer

10) C

For weak acid vs strong acid titrations, pH at equivalence point will be less than 7.

14) B

In acid form , colour of indicator = red

15) B

Al2S3 --------------> 2Al3+ + 3S2-

   2s 3s

Ksp = (2s)2 (3s)3

= 108s5

17) A

Al(OH)3 -----------> Al3+ + 3OH-

s 3s s = molar solubility of Al(OH)3

Ksp = s (3s)3

1.8 x10-32 = 27s4

s = 0.51 x 10-8

= 5.1 x 10-9 M

Therefore,

concentration of Al3+ = 5.1 x 10-9 M

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