Answer the questions on acids, bases, pH and buffers. Questions and Problems Q1

Question

Answer the questions on acids, bases, pH and buffers.
Questions and Problems Q1 Complete the following table: H,0*1 TOH pH Acidic, Basic, or Neutral'? 2.0x10-6 9.8 3.5x10-3 O2 A solution has a [OH-]-4.0x10-5 M. What are the [H3O+] and the pH of the solution? A sample of 0.0084 mol of HCl is dissolved in water to make a 1500-mL solution. Calculate the molarity of the HCl solution, the [H30*1, and the pH. For a strong acid such as HCl, the [H30 is the same as the molarity of the HCI solution Q3 HCI(aq) + H2O(l)- -H,0+ (aq) + ?? (aq)

Explanation / Answer

Ans 1

Part a

[H3O+] = 2.0 x 10^-6

pH = - log [H3O+]

= - log (2.0 x 10^-6)

= 5.7 < 7 (acidic)

pOH = 14 - pH = 14 - 5.7 = 8.3

[OH-] = 10^-pOH = 10^(-8.3) = 5.01 x 10^-9

Part b

pH = 9.8 > 7 (basic)

pOH = 14 - 9.8 = 4.2

pH = - log [H3O+]

[H3O+] = 10^-pH = 10^(-9.8) = 1.58 x 10^-10

[OH-] = 10^-pOH = 10^(-4.2) = 6.31 x 10^-5

Part c

[OH-] = 3.5 x 10^-3

pOH = - log [OH-] = - log (3.5 x 10^-3) = 2.5

pH = 14 - pOH = 14 - 2.5 = 11.5 > 7 (basic)

[H3O+] = 10^-pH = 10^(-11.5) = 3.16 x 10^-12

Part d

Neutral

pH = 7

pOH = 14 - 7 = 7

[H3O+] = 10^-pH = 10^(-7) = 1.0 x 10^-7

[OH-] = 10^-pOH = 10^(-7) = 1.0 x 10^-7

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