Judith Herzfeld 1996,1998. These exercises are provided here for classroom and study use only. All other uses are copyright protected.

Transcription

1 Judith Herzfeld 1996,1998 These exercises are provided here for classroom and study use only. All other uses are copyright protected.

2 According to Bronsted-Lowry Theory, which of the following is not an acid? (a) HCOOH (b) HS (c) NH + 4 (d) CH 4

3 According to Bronsted-Lowry Theory, which of the following is a base? (a) HCN (b) CH 4 (c) H 2 S (d) NH 3

4 The equilibrium constant for which of the following reactions in water is an acidity constant? (a) NH H 2 O NH 3 + H 3 O + (b) NH 3 + H 2 O NH OH (c) HCOO + H 3 O + HCOOH + H 2 O (d) HCN + OH CN + H 2 O

5 K a (HCOOH) is the equilibrium constant for which of the following reactions in water? (a) HCOOH + NH 3 HCOO + NH 4 + (b) HCOOH + H 2 O HCOO + H 3 O + (c) HCOO + H 3 O + HCOOH + H 2 O (d) HCOOH + OH HCOO + H 2 O

6 K a (HS ) is the equilibrium constant for which of the following reactions in water? (a) HS + OH H 2 O + S 2 (b) HS + H 2 O H 3 O + + S 2 (c) HS + H 2 O OH + H 2 S (d) HS + H 3 O + H 2 O + H 2 S

7 K b (HS ) is the equilibrium constant for which of the following reactions in water? (a) HS + OH H 2 O + S 2 (b) HS + H 2 O H 2 S + OH (c) HS + H 3 O + H 2 O + H 2 S (d) HS + H 2 O H 3 O + + S 2

8 The equilibrium constant for the reaction NH OH NH 3 + H 2 O is (a) K a (NH 4 + ) (b) K b (NH 4 + ) (c) 1 / K a (NH 3 ) (d) 1 / K b (NH 3 )

9 Which of the following is the strongest acid? (a) H 3 AsO 4 (b) H 2 AsO 4 (c) HAsO 2 4 (d) AsO 3 4

10 The following figure shows the fractions of the protonated (HA) and deprotonated (A ) forms of two monoprotic acids. fraction 1 a b c d log([h3o+]) Which line represents the protonated form of the stronger acid?

11 The following figure shows the fractions of the four forms of a triprotic acid H 3 A. 1 a b c d log ([H3O+]) Which line represents A 3?

12 The following figure shows the fractions of the protonated and deprotonated forms of two bases. b c fraction a d log ([OH-]) Which curve represents the protonated form of the stronger base?

13 If a 1M solution was prepared of each of the following acids, which would have the highest [H 3 O + ]? (a) CH 3 COOH (K a = 1.76 x 10 5 M) (b) HF (K a = 7.2 x 10 4 M) (c) HCOOH (K a = 1.8 x 10 4 M) (d) HOCl (K a = 3.5 x 10 8 M)

14 When an acid HA is dissolved in water, which is not true? (a) The greater the total concentration of the acid, the greater [A ]. (b) The greater the total concentration of the acid, the greater [HA]. (c) The greater the total concentration of the acid, the greater [H 3 O + ]. (d) The greater the total concentration of the acid, the greater the degree of dissociation.

15 An acid is fully dissociated when the total concentration of acid in all forms is (a) >> K a (b) ~ K a (c) << K a

16 In a 1 M solution of HClO 2 (K a = 1 x 10 2 M), [H 3 O + ] will be (a) 1 M (b) 1 x 10 1 M (c) 1 x 10 2 M

17 Which of the following acid solutions has the higher [H 3 O + ]? (a) 1 x 10 3 M HIO 3 (K a = 1.6 x 10 1 M) (b) 1 M HClO 2 (K a = 1.1 x 10 2 M)

18 Which of the following acid solutions has the higher [H 3 O + ]? (a) 1 x 10 3 M HClO (K a = 3.0 x 10 8 M) (b) 1 x 10 4 M HClO 2 (K a = 1.1 x 10 2 M)

19 The ion product of water varies with temperature as follows T( C) K w (M 2 ) x x x We can conclude that as water is heated, (a) [H 3 O + ] and [OH ] both decrease (b) [H 3 O + ] and [OH ] both increase (c) [H 3 O + ] increases and [OH ] decreases (d) [H 3 O + ] decreases and [OH ] increases

20 At 25 C, a M solution of HCl has a [OH ] of (a) x M (b) x M (c) x M (d) x M

21 At 25 C, a 1.1 M solution of HClO 2 (K a = 1.1 x 10 2 M) has a [OH ] of (a) 9 x M (b) 9 x M (c) 9 x M (d) 8 x M

22 A solution has ph= The [H + ] in this solution is (a) 1.5 x M (b) 6.6 x M (c) 1.5 x 10 5 M (d) 6.6 x 10 4 M The [OH ] in this solution is (a) 1.5 x M (b) 6.6 x M (c) 1.5 x 10 5 M (d) 6.6 x 10 4 M

23 A solution has [OH ] =4.8 x 10 3 M. Its ph is (a) 11.7 (b) 8.4 (c) 4.8 (d) 2.3

24 The ph of a M HA solution is The K a for HA is (a) x M (b) x 10 5 M (c) 4.00 x M (d) 4.00 x 10 5 M

25 The conjugate base of HS is (a) S 2 (b) H 2 S

26 The conjugate acid of H 2 PO 4 is (a) HPO 4 2 (b) H 3 PO 4

27 All of the following are acid base conjugate pairs except (a) HONO, NO 2 (b) CH 3 NH 3 +, CH 3 NH 2 (c) C 6 H 5 COOH, C 6 H 5 COO (d) H 3 O +, OH

28 K b (HC 2 O 4 ) = (a) 1 / K a (H 2 C 2 O 4 ) (b) 1 / K a (C 2 O 4 2 ) (c) K w / K a (H 2 C 2 O 4 ) (d) K w / K a (C 2 O 4 2 )

29 Which of the following is the strongest base? (a) H 3 AsO 4 (b) H 2 AsO 4 (c) HAsO 2 4 (d) AsO 3 4

30 Which of the following acids has the strongest conjugate base? (a) HClO 4 (b) HClO 3 (c) HClO 2 (d) HClO

31 Given that K a (C 5 H 5 NH + ) = 5.6 x 10 6 M K a (HCOOH) = 1.77 x 10 4 M the salt pyridinium formate (C 5 H 5 NH + HCOO ) is (a) acidic (b) basic (c) neutral

32 Given that K a (H 3 PO 4 ) = 7.5 x 10 3 M K a (H 2 PO 4 ) = 6.23 x 10 8 M K a (HPO 2 4 ) = 2.2 x M the salt NaH 2 PO 4 is (a) acidic (b) basic (c) neutral the salt Na 2 H 2 PO 4 is (a) acidic (b) basic (c) neutral

33 NH 4 NO 3 is (a) acidic (b) basic (c) neutral [H 3 O + ] in a 0.1 M aqueous solution of this salt is obtained by solving 2 (a) x 01. M = K x a (NH 4 + ) (b) x2 01. M = K x a (HNO 3 ) (c) x2 01. M = K x b (NH 3 ) (d) x2 01. M = K x b (NO 3 )

34 KCN is (a) acidic (b) basic (c) neutral [OH ] in a 0.5 M aqueous solution of this salt is obtained by solving (a) x2 05. M = K x a (K+ ) (b) x2 05. M = K x a (HCN) (c) x2 05. M = K x b (KOH) (d) x2 05. M = K x b (CN )

35 Given that K a (CH 3 NH + 3 ) = 2.38 x M K a (HCN) = 4.9 x M K a (HOAc) = 1.8 x 10 5 M K a (NH + 4 ) = 5.7 x M which of the following solutions has the highest ph? (a) 0.1M CH 3 NH 3 Cl (b) 0.1M NaCN (c) 0.1M NH 4 NO 3 (d) 0.1M NaOAc The lowest ph?

36 The equilibrium constant for the reaction HONO (aq) + CN (aq) HCN (aq) + ONO (aq) is 1.1 x M. This value indicates that (a) CN is a stronger base than ONO (b) HCN is a stronger acid than HONO (c) the conjugate base of HONO is ONO (d) the conjugate acid of CN is HCN

37 The equilibrium constant for the reaction HClO 2 (aq) + NO 2 (aq) HNO 2 (aq) + ClO 2 (aq) is (a) K a (HClO 2 ) K b (NO 2 ) (b) K a (HNO 2 ) K b (ClO 2 ) (c) K a (HClO 2 ) / K a (HNO 2 ) (d) K b (ClO 2 ) / K b (NO 2 )

38 [NH 3 ] and [NH 4 + ] will be equal when [H 3 O + ] is (a) K a (NH 4 + ) (b) K b (NH 3 ) (c) 1 / K a (NH 4 + ) (d) 1 / K b (NH 3 )

39 Methyl orange has a pk a of 3.7. It will change color when the [H 3 O + ] is in the vicinity of (a) 3.7 M (b) 10.3 M (c) M (d) M

40 Bromthymol blue changes color when the ph is in the vicinity of 7.1. It s K a is (a) 7.1 M (b) 6.9 M (c) M (d) M

41 A flask contains 100 ml of 0.1 M HOAc. To prepare a buffer with ph=pk a (HOAc) which of the following samples should be added to the flask? (a) 50 ml of 0.2 M Ba(OAc) 2 (b) 200 ml of 0.1 M Ba(OAc) 2 (c) 25 ml of 0.2 M Ba(OAc) 2 (d) 100 ml of 0.1 M Ba(OAc) 2

42 Which mixture has a different ph from the others? (a) 1 L of 1 M NaOH + 1 L of 2 M HCN (b) 1 L of 1 M NaCN + 1 L of 1 M HCN (c) 1 L of 1 M NaOH + 2 L of 1 M HCN (d) 1 L of 1 M NaOH + 1 L of 1 M HCN

43 Which of the following mixtures will be a buffer solution when dissolved in 500 ml of water? (a) 0.2 mol C 6 H 5 NH mol HCl (b) (c) (d) 0.2 mol C 6 H 5 NH mol NaOH 0.2 mol C 6 H 5 NH mol HCl 0.2 mol C 6 H 5 NH mol NaOH

44 Which of the following mixtures is a buffer with ph close to pk a (NH 4 + ) (a) (b) (c) (d) 30 ml of 0.1 M NH 4 Cl + 10 ml of 0.1 M NaOH 30 ml of 0.1 M NH 4 Cl + 15 ml of 0.1 M NaOH 30 ml of 0.1 M NH 4 Cl + 20 ml of 0.1 M NaOH 30 ml of 0.1 M NH 4 Cl + 30 ml of 0.1 M NaOH

45 A weak base, B, has a basicity constant K b = 2 x 10-5 M. The ph of any solution in which [B]=[BH + ] is (a) 4.7 (b) 5.3 (c) 8.7 (d) 9.3

46 The following figure shows the composition diagram of H 3 PO ph Which ph cannot be buffered well by phosphate? (a) 2 (b) 5 (c) 7 (d) 13

47 The following figure shows the composition diagram of H 3 PO ph To make a ph 7 buffer which mixture would you use? (a) Na 3 PO 4 and Na 2 HPO 4 (b) Na 2 HPO 4 and NaH 2 PO 4 (c) NaH 2 PO 4 and H 3 PO 4 For a ph 2 buffer?

48 A buffer is prepared that contains 1 mol NaOAc and 1 mol HOAc. When 0.5 mol of NaOH is added, the ph (a) doubles (b) increases by log 2 = (c) increases by log 3 = (d) depends on the volume

49 ml of a solution of a solution of X is titrated with a 0.1 M solution of Y giving volume Y (ml) Y is a (a) strong base (b) strong acid (c) weak base (d) weak acid The initial concentration of X is (a) 1 M (b) 0.1 M (c) 0.05 M (d) 0.01 M X is a (a) strong base (b) strong acid (c) weak base (d) weak acid

50 ml samples of two different acids are titrated with 0.1 M NaOH giving a b volume NaOH (ml) Which is the more concentrated acid? Which is the weaker acid? The molarity of acid a is (a) 0.01 (b) 0.1 (c) 1 (d) 10 The molarity of acid b is (a) 0.01 (b) 0.02 (c) 0.05 (d) 0.2

51 In titrating 0.10 M HCOOH (formic acid) with 0.10 M NaOH, the solution at the equivalence point is (a) 0.10 M HCOONa (b) 0.05 M HCOOH (c) 0.05 M HCOONa (d) 0.05 M NaOH

52 A 50 ml sample of 30 mm Ba(OH) 2 is titrated with 30 mm HCl. The solution at the equivalence point is (a) 60 mm BaCl 2 (b) 30 mm BaCl 2 (c) 15 mm BaCl 2 (d) 10 mm BaCl 2

53 A 10 ml sample of a 0.2 M solution of the weak diprotic acid H 2 X is titrated with 0.2 M KOH. The solution at the second equivalence point is (a) 0.2 M KHX (b) 0.2 M K 2 X (c) 0.1 M KHX (d) M K 2 X