pH is a logarithmic scale used to indicate the hydrogen ion concentration, [H^+]

Question

pH is a logarithmic scale used to indicate the hydrogen ion concentration, [H^+] of a solution: pH = -log [H^+] Due to the autoionization of water, in any aqueous solution, the hydrogen ion concentration and the hydroxide ion concentration, [OH^-] are related to each other by the K_w of water. K_w = [H^+][OH^-] = 1.00 times 10^-14 where 1.00 times 10^-14 is the value at approximately 297 K. Based on this relation, the pH and pOH are also related to each other as 14.00 = pH + pOH The temperature for each solution is carried out at approximately 297 K where K_w = 1.00 times 10^-14. 0.55 g of hydrogen chloride (HCl) is dissolved in water to make 3.0 L of solution. What is the pH of the resulting hydrochloric acid solution? Express the pH numerically to two decimal places. pH = 0.90 g of sodium hydroxide (NaOH) pellets are dissolved in water to make 6.0 L of solution. What is the pH of this solution? Express the pH numerically to two decimal places. pH =

Explanation / Answer

Let us convert into moles

= 0.55 / 36.45 = 0.015089 Moles

The disassociation equation is

HCl =====> H+    + Cl-

Let us calculate the molalrity of the solution

Molarity=moles/volume

Molarity = 0.015089 Moles / 3.0 L = 0.005029 M

The equation for pH is pH=-log[H+]

pH = -log 0.005029

pH = 2.29

PART B

Let us convert into moles

= 0.9 / 40 = 0.0225 Moles

The disassociation equation is

NaOH =====> Na+    + OH-

Let us calculate the molalrity of the solution

Molarity=moles/volume

Molarity = 0.0225 Moles / 6.0 L = 0.00375 M

The equation for pH is pOH=-log[OH-]

pOH = -log 0.00375

pOH = 2.425

pH + pOH = 14

pH = 14- pOH

pH = 14- 2.425

pH = 11.57

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