CHM 4, SECT.009 TEST 2: CHAP\'S 15 &16 wer all questions in the examination book

Question

CHM 4, SECT.009 TEST 2: CHAP'S 15 &16 wer all questions in the examination booklet (10 pts. each) 1) Identify the conjugate acid-base pairs in each reaction: a) HC,H,O, + CH,NH, CH,O,+ CH,NH, b) HNO, +H,0 NO, +o 2) Calculate the correct pH of each solution: a) 7.2 x 10 M Sr(OH) b) 5.2 x 10 HNO, 3) Calculate the correct pH of a 0.1 3 M solution of C,H,NH' (K,-5.6 x 104). 4 Calculate the pli of a solution made by dissolving 0 5s grams of Naf in 600 ml of water (K,- u)3 1.5 x 10"). 5) A 0.2M solution of C.i,co,H has a plt of 2.44. What is the value of K, for C,H,CO,H? 6) A 28 ml. solution of 0.12 M NaoH is titrated with 0013M ic a) What volume of HCI needs to be added to reach the equivalence point? b) What is the pH at the midpoint? c) What is the pll at the equivalence point? WA A 39mL solution of0.15 MHC,HO, (K,= 1.4 x 104) is titrated with 0.12 M NaOH: a) What volume of NaOH needs to be added to reach the equivalence point? b) What is the pH at the midpoint? c) What is the phH at the equivalence point? 8) What is the pH ofa buffer made by mixing 150 ml, of 0.22 M C2H,CIO,H (K, = 1.4 x 103) with 120 mL of 0.25 M NaC,JH,CIO,? Determine the pH of a buffer after the addition of a 10 ml. sample of 1.6 M NaOH to 300 mL of solution which is 0.22 MC,H,O,H (K, 1.8 x 10') and 0.20 M Na C,H,O 2 10) How many grams of Nall,PO, must be added to a 250 ml. solution of H,po, (K,-7.5 x 10") to produce a buffer with a pH of 2.25?

Explanation / Answer

ans 1) a)   HC2H3O2 + CH3NH2 ------ C2H3O2- + CH3NH3+

if acid looses proton it becomes conjugate base and vice versa

So, HC2H3O2 is acid and C2H3O2- is conjugate base and CH3NH2 is base and CH3NH3+ is conjugate acid.

b) HNO2 +H2O --- NO2- + H3O+

if acid looses proton it becomes conjugate base and vice versa

So, HNO2 is acid and NO2- is conjugate base and H2O is base and H3O+ is conjugate acid.

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