Question

i need help answering these questiona the graph helps to answer #1

Experiment 4 Advance Study Assignment: pH, Its Measurement and Applications 1. A solution of a weak acid was tested with the indicators used in this experiment. The colors observed were as follows: Methyl violet Thymol blue Methyl yellow violet orange red Congo red Bromcresol green yellow Chapter 4: pH Measurements-Buffers and Their Properties What is the approximate pH of the solution? 2. An aqueous solution of NH, has a pH of 11.6. The ammonia (NH) molecule is the conjugate base of the NH, (called "ammonium") ion. Write the net ionic equation for the reaction that makes an aqueous solution of NH, basic. (Eq. 5.) 3. The pH of a 0.10 M HOBr solution is 4.8. a. What is (H') in that solution? b. What is [OBr")? What is [HOBr]? (Where do the H and Br" ions come from?) M; c. What is the value of K for HOBr? What is the value of pK,?

Answer 1

1) ans- From the graph we can identify that the pH of the acid should be approximately equal to 3 as the colour changes for

methyl violet- violet ,ie,pH>2

thymol blue-pH>3

methyl yellow-4

congo red-pH would be similiar to 3

Bromcresol green-pH  <4

hence if we take the average of all the pH,it would be approximately 3.

2)ans-

A07SHEK 2) the hot wnic aquation that makes an aqueous solu of Nie basic is given below! Ny 199 + OH - NH3 lag) + H2001 Baus (a) Here given ph of 0.10m hobe is 4.8 We know, pH-tog [ht] .. [ut] - antilog LpH - antilop [4.8 ] [4+]= (10) PH - 1048 [nt] = 1.588 165m 16 Ang Ho Br will be duriouates into equal quantities of Hitions and [OB) ions. Thus [o Ber] = [pt7 [OB] = 1.58410 sm Now concentration of horr = concentration before dissouation - concentration ofles discrietia i - 0.10M - 1.58 x 105M Dilomas 0.10>>> 1.58x105 (1) Ane We know that Ka= [ut] [OB67 [HoBa] ka= [ 1.5805) [ 1.58x10-5) ka = 2.60 x26q10:10) Now, pha= -log(ka) apka= -log(2.50 x109) = 8.6