Question

A. 200.0 mL of 0.025 M HBr (aq) is diluted with water to a final volume of 500.0 mL. What's the final pH?

B. What is the final pH when 60.0 mL solution of 0.10 M PIPES (pKa = 6.8) is mixed with 120.0 mL of 0.10M Na PIPES.

C. How much gas in moles would a canister of gas at 50.0°C hold with a volume of 50.0 L at 1.00 atm pressure?

Answer 1

A)

volume V1 = 200.0 mL

concentration C1 = 0.025 M

volume V2 = 500.0 mL

C1 V1 = C2 V2

0.025 x 200 = C2 x 500

C2 = 0.1

final concnetration of HBr = 0.10 M

pH = -log [H+] = -log (0.1)

pH = 1.0

2)

mmoles of PIPES = 60 x 0.1 = 6

mmoles of NaPIPES = 120 x 0.1 = 12

pH = pKa + log [salt / acid]

     = 6.8 + log [12 / 6]

pH = 7.1

c)

temperature = 50 oC = 323 K

volume = 50.0 L

pressure = 1.00 atm

P V = n R T

1 x 50 = n x 0.0821 x 323

n = 1.89

moles of gas = 1.89