Boric acid(H3BO3) has a Ka of 5.8x10^-10 and phosphoric acid (H3PO4) has a Ka1 o

Question

Boric acid(H3BO3) has a Ka of 5.8x10^-10 and phosphoric acid (H3PO4) has a Ka1 of 7.5x10^-3. Using the information provided in the table below select an indicator for a titration to endpoint of the first proton removal. Then explain Your answer.

Indicator
*Bromophenol Blue (pH range= 3.0 - 4.6)
*Bromoscresol Purple (pH range= 5.2 -6.8)
*Nile blue (pH range= 10.1-11.1)

H3BO3 Indicator?
H3PO4 Indicator?

Explain:

(There's no titration curve. this is all the question)

Short answer. Aents as emarked. Show werk for na redit ae caksition problems. Mloe osio- ADa) haa e Ka of5.0mWs and phogh ricocewad has a Kal of 7.5x, using the ite 3)autane, C Mae has a boling point or-1and an erapy dr vaportation of 22.44 kamel what s the eraopy change of this reverstle process?(2p0 A+-0.0125 as AS, 22, 972

Explanation / Answer

For first equivalence point

pH = pKa1 + pKa2

For H3BO3

pKa1 = 9.24

pKa2 = 12.4

pH =( 9.24 + 12.4)/2 = 10.82

Nile blue pH range ( 10.1 - 11.1) cover this pH

H3BO3 indicator is Nile blue

For H3PO4

pKa1 = 2.15

pKa2 = 7.20

pH =( 2.15 + 7.20 )/2= 4.68

Bromophenol blue range (3.0 to 4.6) nearly cover this pH

So, H3PO4 indicator is Bromophenol blue

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